Journal ArticleJournal of the Korean Physical Society · April 1, 2023
We study the properties of a quantum critical region of an XXZ model in two dimensions. The quantum critical point at zero temperature evolves as the temperature increases. Using the quantum Monte Carlo method with stochastic series expansions, we simulate ...
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Journal ArticlePhysical Review B · October 25, 2021
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We find the nonlinear conductance of a dissipative resonant level in the nonequilibrium steady state near its quantum critical point. The system consists of a spin-polarized quantum dot connected to two resistive leads that provide ohmic dissipation. We fo ...
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Journal ArticlePhysical Review A · March 24, 2021
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We study a minimal model that has a driven-dissipative quantum phase
transition, namely a Kerr non-linear oscillator subject to driving and
dissipation. Using mean-field theory, exact diagonalization, and the Keldysh formalism, we analyze the critical phen ...
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Journal ArticlePhysical Review B · July 1, 2020
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We analyze a system in which a topological Majorana zero mode (MZM) combines with a MZM produced by quantum frustration. At the boundary between the topological and non-topological states, a MZM does not appear. The system that we study combines two parts, ...
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Journal ArticleNature Physics · May 18, 2020
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The search for topological excitations such as Majorana fermions has spurred interest in the boundaries between distinct quan- tum states. Here, we explore an interface between two prototypical phases of electrons with conceptually different ground states: ...
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Journal ArticlePhysical Review Letters · April 9, 2019
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Maximally entangled two-qubit states (Bell states) are of central importance in quantum technologies. We show that heralded generation of a maximally entangled state of two intrinsically open qubits can be realized in a one-dimensional (1D) system through ...
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Journal ArticlePhys Rev Lett · February 22, 2019
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Excitation of a bound state in the continuum (BIC) through scattering is problematic since it is by definition uncoupled. Here, we consider a type of dressed BIC and show that it can be excited in a nonlinear system through multiphoton scattering and delay ...
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Journal ArticlePhysical Review A · October 8, 2018
Understanding large-scale interacting quantum matter requires dealing with the huge number of quanta that are produced by scattering even a few particles against a complex quantum object. Prominent examples are found from high-energy cosmic ray showers, to ...
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Journal ArticleNew Journal of Physics · April 16, 2018
We investigate the open dynamics of a qubit due to scattering of a single photon in an infinite or semi-infinite waveguide. Through an exact solution of the time-dependent multi-photon scattering problem, we find the qubitʼs dynamical map. Tools of open qu ...
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Journal ArticlePhysical Review A · February 7, 2018
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We obtain photon statistics by using a quantum jump approach tailored to a system in which one or two qubits are coupled to a one-dimensional waveguide. Photons confined in the waveguide have strong interference effects, which are shown to play a vital rol ...
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Journal ArticlePhysical Review A · July 21, 2017
We investigate interference and correlation effects when several detuned emitters are placed along a one-dimensional photonic waveguide. Such a setup allows multiple interactions between the photons and the strongly coupled emitters, and underlies proposed ...
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Journal ArticlePhys Rev Lett · February 3, 2017
We show that placing a quantum system in contact with an environment can enhance non-Fermi-liquid correlations, rather than destroy quantum effects, as is typical. The system consists of two quantum dots in series with two leads; the highly resistive leads ...
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Journal ArticlePhysical Review A · March 28, 2016
We investigate the quantum dynamics of a generic model of light-matter interaction in the context of high-impedance waveguides, focusing on the behavior of the photonic states generated in the waveguide. The model treated consists simply of a two-level sys ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · October 6, 2015
A local interaction between photons can be engineered by coupling a nonlinear system to a transmission line. The required transmission line can be conveniently formed from a chain of Josephson junctions. The nonlinearity is generated by side-coupling this ...
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Journal ArticlePhysical Review A - Atomic, Molecular, and Optical Physics · May 22, 2015
We study two-level systems (2LS) coupled at different points to a one-dimensional waveguide in which one end is open and the other is either open (infinite waveguide) or closed by a mirror (semi-infinite). Upon injection of two photons (corresponding to we ...
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Journal ArticleEPJ Quantum Technology · December 1, 2014
For a one-dimensional (1D) waveguide coupled to two or three qubits, we show that the photon-photon correlations have a wide variety of behavior, with structure that depends sensitively on the frequency and on the qubit-qubit separation L. We study the cor ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · August 7, 2014
We develop a systematic variational coherent-state expansion for the many-body ground state of the spin-boson model, in which a quantum two-level system is coupled to a continuum of harmonic oscillators. Energetic constraints at the heart of this technique ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · June 27, 2014
We consider theoretically the transport properties of a spinless resonant electronic level coupled to strongly dissipative leads, in the regime of circuit impedance near the resistance quantum. Using the Luttinger liquid analogy, one obtains an effective H ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · March 18, 2014
The key feature of a quantum spin coupled to a harmonic bath - a model dissipative quantum system - is competition between oscillator potential energy and spin tunneling rate. We show that these opposing tendencies cause environmental entanglement through ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · February 18, 2014
We study tunneling through a resonant level connected to two dissipative bosonic baths: one is the resistive environment of the source and drain leads, while the second comes from coupling to potential fluctuations on a resistive gate. We show that several ...
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Journal ArticlePhys Rev Lett · August 30, 2013
We propose a new scheme for quantum computation using flying qubits--propagating photons in a one-dimensional waveguide interacting with matter qubits. Photon-photon interactions are mediated by the coupling to a four-level system, based on which photon-ph ...
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Journal ArticlePhysical Review Letters · July 22, 2013
We develop an approach to realizing a topological phase transition and non-Abelian braiding statistics with dynamically induced Floquet Majorana fermions (FMFs). When the periodic driving potential does not break fermion parity conservation, FMFs can encod ...
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Journal ArticlePhysical Review Letters · June 11, 2013
We study the quantum phase transition of interacting electrons in quantum wires from a one-dimensional (1D) linear configuration to a quasi-1D zigzag arrangement using quantum Monte Carlo methods. As the density increases from its lowest values, first, the ...
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Journal ArticlePhysical review letters · March 2013
We study photon-photon correlations and entanglement generation in a one-dimensional waveguide coupled to two qubits with an arbitrary spatial separation. To treat the combination of nonlinear elements and 1D continuum, we develop a novel Green function me ...
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Journal ArticleOptics letters · March 2013
We investigate a decoy-state quantum key distribution (QKD) scheme with a sub-Poissonian single-photon source, which is generated on demand by scattering a coherent state off a two-level system in a one-dimensional waveguide. We show that, compared to cohe ...
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Journal ArticlearXiv · January 30, 2013
The coupling of a qubit to a macroscopic reservoir plays a fundamental role in understanding the complex transition from the quantum to the classical world. Considering a harmonic environment, we use both intuitive arguments and numerical many-body quantum ...
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Journal ArticleNature Physics · January 1, 2013
A quantum phase transition is an abrupt change between two distinct ground states of a many-body system, driven by an external parameter. In the vicinity of the quantum critical point (QCP) where the transition occurs, a new phase may emerge that is determ ...
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Journal ArticleEur. Phys. J. B · October 16, 2012
We consider the low temperature regime of the mesoscopic Kondo problem, and
in particular the relevance of a Fermi-liquid description of this regime. Using
two complementary approaches -- a mean field slave fermion approximation on the
one hand and a Fermi ...
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Journal ArticleNature · August 2012
A Luttinger liquid is an interacting one-dimensional electronic system, quite distinct from the 'conventional' Fermi liquids formed by interacting electrons in two and three dimensions. Some of the most striking properties of Luttinger liquids are revealed ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · April 27, 2012
We study the Anderson impurity problem in a mesoscopic setting, namely the "Anderson box," in which the impurity is coupled to finite reservoir having a discrete spectrum and large sample-to-sample mesoscopic fluctuations. Note that both the weakly coupled ...
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Journal ArticlePhysical Review A - Atomic, Molecular, and Optical Physics · April 19, 2012
We study the generation of strongly correlated photons by coupling an atom to photonic quantum fields in a one-dimensional waveguide. Specifically, we consider a three-level or four-level system for the atom. Photon-photon bound states emerge as a manifest ...
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Chapter · January 1, 2012
Introduction The existence of efficient quantum error correction (QEC), combined with the concept of the accuracy threshold [G98, KLZ98a], inspired confidence that reliable quantum computation is achievable in principle. However, a key point to understand ...
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Journal ArticleEPL · January 1, 2012
We study mesoscopic fluctuations in a system in which there is a continuous connection between two distinct Fermi liquids, asking whether the mesoscopic variation in the two limits is correlated. The particular system studied is an Anderson impurity couple ...
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Journal ArticlePhysical Review Letters · November 21, 2011
The manipulation of individual, mobile quanta is a key goal of quantum communication; to achieve this, nonlinear phenomena in open systems can play a critical role. We show theoretically that a variety of strong quantum nonlinear phenomena occur in a compl ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · November 16, 2011
We propose an experimental setup for detecting a Majorana zero mode consisting of a spinless quantum dot coupled to the end of a p-wave superconducting nanowire. The Majorana bound state at the end of the wire strongly influences the conductance through th ...
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Journal ArticlePramana - Journal of Physics · November 1, 2011
Two important themes in nanoscale physics in the last two decades are correlations between electrons and mesoscopic fluctuations. Here we review our recent work on the intersection of these two themes. The setting is the Kondo effect, a paradigmatic exampl ...
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Journal ArticlePhysical Review A - Atomic, Molecular, and Optical Physics · December 14, 2010
Strong coupling between a two-level system (TLS) and bosonic modes produces dramatic quantum optics effects. We consider a one-dimensional continuum of bosons coupled to a single localized TLS, a system which may be realized in a variety of plasmonic, phot ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · October 18, 2010
The concept of the "Kondo box" describes a single spin, antiferromagnetically coupled to a quantum dot with a finite level spacing. Here, a Kondo box is formed in a carbon nanotube interacting with a localized electron. We investigate the spins of its firs ...
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Journal ArticlePhysical Review A - Atomic, Molecular, and Optical Physics · August 31, 2010
We obtain an upper bound on the time available for quantum computation for a given quantum computer and decohering environment with quantum error correction implemented. First, we derive an explicit quantum evolution operator for the logical qubits and sho ...
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Journal ArticleSemiconductor Science and Technology · February 23, 2010
We study the conductance of mesoscopic graphene rings in the presence of a perpendicular magnetic field by means of numerical calculations based on a tight-binding model. First, we consider the magnetoconductance of such rings and observe the Aharonov-Bohm ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · November 2, 2009
We study interaction-induced localization of electrons in an inhomogeneous quasi-one-dimensional system-a wire with two regions, one at low density and the other high. Quantum Monte Carlo techniques are used to treat the strong Coulomb interactions in the ...
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Journal ArticleNew Journal of Physics · September 30, 2009
We study the conductance through two types of graphene nanostructures: nanoribbon junctions in which the width changes from wide to narrow, and curved nanoribbons. In the wide-narrow structures, substantial reflection occurs from the wide-narrow interface, ...
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Journal ArticleNano letters · March 2009
Molecular nanojunctions may support efficient thermoelectric conversion through enhanced thermopower. Recently, this quantity has been measured for several conjugated molecular nanojunctions with gold electrodes. Considering the wide variety of possible me ...
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Journal ArticlePhysical review letters · February 2009
We study the symmetry classes of graphene quantum dots, both open and closed, through the conductance and energy level statistics. For abrupt termination of the lattice, these properties are well described by the standard orthogonal and unitary ensembles. ...
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Journal ArticlePhys. Rev. B · 2009
We consider an “impurity” with a spin degree of freedom coupled to a finite reservoir of non-interacting electrons, a system which may be realized by either a true impurity in a metallic nano-particle or a small quantum
dot coupled to a large one. We show ...
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Journal ArticleNano letters · October 2008
Quantum interference in coherent transport through single molecular rings may provide a mechanism to control the current in molecular electronics. We investigate its applicability, using a single-particle Green function method combined with ab initio elect ...
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Journal ArticlePhysical Review A - Atomic, Molecular, and Optical Physics · July 9, 2008
We analyze the long-time behavior of a quantum computer running a quantum error correction (QEC) code in the presence of a correlated environment. Starting from a Hamiltonian formulation of realistic noise models, and assuming that QEC is indeed possible, ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 2, 2008
We argue that Coulomb blockade phenomena are a useful probe of the crossover to strong correlation in quantum dots. Through calculations at low density using variational and diffusion quantum Monte Carlo (up to rs ∼55), we find that the addition energy sho ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · December 18, 2007
We study Fermi edge singularities in photoabsorption spectra of generic mesoscopic systems such as quantum dots or nanoparticles. We predict deviations from macroscopic-metallic behavior and propose experimental setups for the observation of these effects. ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · December 12, 2007
We discuss decoherence in charge qubits formed by multiple lateral quantum dots in the framework of the spin-boson model and the Born-Markov approximation. We consider the intrinsic decoherence caused by the coupling to bulk phonon modes. Two distinct quan ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · November 30, 2007
We obtain analytic formulas for the spacing between conductance peaks in the Coulomb blockade regime based on the universal Hamiltonian model of quantum dots. Random matrix theory results are developed in order to treat correlations between two and three c ...
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Journal ArticleThe Journal of chemical physics · October 2007
We investigate electron transport through single conjugated molecules--including benzenedithiol, oligophenylene ethynylenes of different lengths, and a ferrocene-containing molecule sandwiched between two gold electrodes with different contact structures-- ...
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Journal ArticlePhysical review letters · October 2007
The transparency of contacts between conjugated molecules and metallic single-walled carbon nanotubes is investigated using a single-particle Green's function method which combines a Landauer approach with ab initio density functional theory. We find that ...
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Journal ArticleThe Journal of chemical physics · October 2007
In the context of investigating organic molecules for molecular electronics, doping molecular wires with transition metal atoms provides additional means of controlling their transport behavior. The incorporation of transition metal atoms may generate spin ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · August 28, 2007
We study the development of electron-electron correlations in circular quantum dots as the density is decreased. We consider a wide range of both electron number, N≤20, and electron gas parameter, rs 18, using the diffusion quantum Monte Carlo technique. F ...
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Journal ArticleThe Journal of chemical physics · May 2007
The effect of the exchange-correlation potential in ab initio electron transport calculations is investigated by constructing optimized effective potentials using different energy functionals or the electron density from second-order perturbation theory. T ...
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Journal ArticlePhysical review letters · January 2007
We analyze the problem of a quantum computer in a correlated environment protected from decoherence by quantum error correction using a perturbative renormalization group approach. The scaling equation obtained reflects the competition between the dimensio ...
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Journal ArticleJournal of Computational and Theoretical Nanoscience · December 29, 2006
A fully self-consistent method combining density functional theory (DFT) and nonequilibrium Green function approach for calculating electron transport through molecular devices is reviewed. It uses periodic boundary conditions for DFT and treats the leads ...
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Journal ArticlePhysical review letters · July 2006
We study the decoherence of a quantum computer in an environment which is inherently correlated in time and space. We first derive the nonunitary time evolution of the computer and environment in the presence of a stabilizer error correction code, providin ...
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Journal ArticleJournal of the American Chemical Society · May 2006
Analogous to a quantum double-dot system, diblock structured molecules could also show negative differential resistance (NDR). Using combined density functional theory and nonequilibrium Green function technique, we show that molecular-level crossing in a ...
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Journal ArticleThe Journal of chemical physics · May 2006
We address the quality of electrical contact between carbon nanotubes and metallic electrodes by performing first-principles calculations for the electron transmission through ideal 2- and 3-terminal junctions, thus revealing the physical limit of tube-met ...
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Journal ArticleThe Journal of chemical physics · January 2006
We study the rectification of current through a single molecule with an intrinsic spatial asymmetry. The molecule contains a cobaltocene moiety in order to take advantage of its relatively localized and high-energy d states. A rectifier with large voltage ...
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Journal ArticlePhys.Rev.Lett. · 2006
Motivated by experiments on double quantum dots, we study the problem of a single magnetic impurity confined in a finite metallic host. We prove an exact theorem for the ground state spin, and use analytic and numerical arguments to map out the spin struct ...
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Journal ArticleProceedings of SPIE - The International Society for Optical Engineering · November 15, 2005
The spin of an electron confined into a lateral semiconductor quantum dot has been proposed as a possible physical realization of a qubit. While the spin has the advantage of large decoherence times, operations with more than one qubit will necessarily inv ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · October 15, 2005
For Coulomb blockade peaks in the linear conductance of a quantum dot, we study the correction to the spacing between the peaks due to dot-lead coupling. This coupling can affect measurements in which Coulomb blockade phenomena are used as a tool to probe ...
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Journal ArticleEurophysics Letters · October 1, 2005
We calculate the mesoscopic fluctuations of the magnetic anisotropy of ferromagnetic nanoparticles; that is, the effect of single-particle interference on the direction of the collective magnetic moment. A microscopic spin-orbit Hamiltonian considered as a ...
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Journal ArticleNano letters · October 2005
A single-molecule spintronic switch and spin valve using two cobaltocene moieties is proposed. Spin-dependent transport through a lead-molecule-lead junction has been calculated using first-principles density functional and nonequilibrium Green function me ...
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Journal ArticleThe Journal of chemical physics · September 2005
Bridging the difference in atomic structure between experiments and theoretical calculations and exploring quantum confinement effects in thin electrodes (leads) are both important issues in molecular electronics. To address these issues, we report here, b ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · July 15, 2005
For generic mesoscopic systems, such as quantum dots or nanoparticles, we study the Anderson orthogonality catastrophe (AOC) and Fermi-edge singularities in photoabsorption spectra in a series of two papers. In the present paper we focus on AOC for a finit ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · July 15, 2005
Despite considerable work on the energy-level and wave function statistics of disordered quantum systems, numerical studies of those statistics relevant for electron-electron interactions in mesoscopic systems have been lacking. We plug this gap by using a ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · June 15, 2005
Here we describe the design, single-molecule transport measurements, and theoretical modeling of a ferrocene-based organometallic molecular wire, whose bias-dependent conductance shows a clear Lorentzian form with magnitude exceeding 70% of the conductance ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · June 15, 2005
We address the issue of accurately treating interaction effects in the mesoscopic regime by investigating the ground-state properties of isolated irregular quantum dots. Quantum Monte Carlo techniques are used to calculate the distributions of ground-state ...
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Journal ArticleThe Journal of chemical physics · February 2005
Using benzene sandwiched between two Au leads as a model system, we investigate from first principles the change in molecular conductance caused by different atomic structures around the metal-molecule contact. Our motivation is the variable situations tha ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2005
We study decoherence of a quantum dot charge qubit due to coupling to piezoelectric acoustic phonons in the Born-Markov approximation. After including appropriate form factors, we find that phonon decoherence rates are one to two orders of magnitude weaker ...
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Journal ArticleThe Journal of chemical physics · January 2005
We investigate the effects of lateral interactions on the conductance of two molecules connected in parallel to semi-infinite leads. The method we use combines a Green function approach to quantum transport with density functional theory for the electronic ...
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Journal ArticleJournal of the American Chemical Society · December 2004
Combining density functional theory calculations for molecular electronic structure with a Green function method for electron transport, we calculate from first principles the molecular conductance of benzene connected to two Au leads through different anc ...
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Journal ArticlePhysical review letters · October 2004
We study the x-ray edge problem for a chaotic quantum dot or nanoparticle displaying mesoscopic fluctuations. In the bulk, x-ray physics is known to produce Fermi-edge singularities-deviations from the naively expected photoabsorption cross section in the ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · March 24, 2004
We study the effect of mesoscopic fluctuations on the magnitude of errors that can occur in exchange operations on quantum dot spin qubits. Midsize double quantum dots, with an odd number of electrons in the range of a few tens in each dot, are investigate ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2004
We study the effect of mesoscopic fluctuations on the magnitude of errors that can occur in exchange operations on quantum dot spin qubits. Midsize double quantum dots, with an odd number of electrons in the range of a few tens in each dot, are investigate ...
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Journal ArticlePhys. Rev. B · October 24, 2003
Kohn-Sham spin-density functional theory provides an efficient and accurate model to study electron-electron interaction effects in quantum dots, but its application to large systems is a challenge. Here an efficient method for the simulation of quantum do ...
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Journal ArticlePhysical review letters · September 2003
Using density-functional theory calculations, we investigate the addition energy (AE) of quantum dots formed of fullerenes or closed single-wall carbon nanotubes. We focus on the connection between symmetry and oscillations in the AE spectrum. In the highl ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2003
We study the effect of the exchange interaction on the Coulomb blockade peak height statistics in chaotic quantum dots. Since exchange reduces the level repulsion in the many-body spectrum, it strongly affects the fluctuations of the peak conductance at fi ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2003
Properties of the Kondo effect in quantum dots depend sensitively on the coupling parameters and so on the realization of the quantum dot—the Kondo temperature itself becomes a mesoscopic quantity. Assuming chaotic dynamics in the dot, we use random matrix ...
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Journal ArticlePhysical review letters · January 2003
We use spin-density-functional theory to study the spacing between conductance peaks and the ground-state spin of 2D model quantum dots with up to 200 electrons. Distributions for different ranges of electron number are obtained in both symmetric and asymm ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2003
Properties of the Kondo effect in quantum dots depend sensitively on the coupling parameters and so on the realization of the quantum dot-the Kondo temperature itself becomes a mesoscopic quantity. Assuming chaotic dynamics in the dot, we use random matrix ...
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Journal ArticlePhysica A: Statistical Mechanics and its Applications · April 1, 2002
Universal statistical aspects of wave scattering by a variety of physical systems ranging from atomic nuclei to mesoscopic systems and microwave cavities are described. A statistical model for the scattering matrix, introduced in the past in the context of ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2002
We study the statistics of the spacing between Coulomb blockade conductance peaks in quantum dots with large dimensionless conductance g. Our starting point is the “universal Hamiltonian”-valid in the (formula presented) limit-which includes the charging e ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2002
We study the statistics of the spacing between Coulomb blockade conductance peaks in quantum dots with large dimensionless conductance g. Our starting point is the "universal Hamiltonian" - valid in the g → ∞ limit - which includes the charging energy, the ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · December 15, 2001
We use random matrix models and a Fermi-liquid approach to investigate the ground state energy of electrons confined to a nanoparticle. Our expression for the energy includes the charging effect, the single-particle energies, and the residual screened inte ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · December 15, 2001
We develop a semiclassical theory of Coulomb blockade peak heights in chaotic quantum dots. Using Berry's conjecture, we calculate peak height distributions and correlation functions. We demonstrate that corrections to the corresponding results of the stan ...
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Journal ArticleSolid State Communications · November 19, 2001
We report that excitonic lasing gain coexists with spontaneous optical emission characteristic of an electron-hole plasma in highly photoexcited one-dimensional semiconductors. The experiments probe quantum T-wire laser structures optimized for high photoe ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · April 18, 2001
We study spin-dependent transport through ferromagnet/normal-metal/ferromagnet double tunnel junctions in the mesoscopic Coulomb-blockade regime. We calculate the conductance in the absence or presence of spin-orbit interaction and for arbitrary orientatio ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · March 13, 2001
We develop a semiclassical density functional theory in the context of quantum dots. Coulomb blockade conductance oscillations have been measured in several experiments using nanostructured quantum dots. The statistical properties of these oscillations rem ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2001
We calculate the Coulomb-blockade peak-spacing distribution at finite temperature using the recently introduced “universal Hamiltonian” to describe the (formula presented) interactions. We show that the temperature effect is important even at (formula pres ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2001
The effect of silicon-oxide interface roughness on the weak-localization magnetoconductance of a silicon metal-oxide-semiconductor field-effect transistor in a magnetic field, tilted with respect to the interface, is studied. It is shown that an electron p ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2001
The effect of silicon-oxide interface roughness on the weak-localization magnetoconductance of a silicon metal-oxide-semiconductor field-effect transistor in a magnetic field, tilted with respect to the interface, is studied. It is shown that an electron p ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2001
We calculate the Coulomb-blockade peak-spacing distribution at finite temperature using the recently introduced "universal Hamiltonian" to describe the e-e interactions. We show that the temperature effect is important even at kBT∼Δ (Δ is the single-partic ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2001
We develop a semiclassical density functional theory in the context of quantum dots. Coulomb blockade conductance oscillations have been measured in several experiments using nanostructured quantum dots. The statistical properties of these oscillations rem ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · 2001
We study spin-dependent transport through ferromagnet/normal-metal/ferromagnet double tunnel junctions in the mesoscopic Coulomb-blockade regime. We calculate the conductance in the absence or presence of spin-orbit interaction and for arbitrary orientatio ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2000
We investigate the spin of the ground state of a geometrically confined many-electron system. For atoms, shell structure simplifies this problem—the spin is prescribed by the well-known Hund’s rule. In contrast, quantum dots provide a controllable setting ...
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Journal ArticleScience (New York, N.Y.) · January 2000
Coherent wave propagation in disordered media gives rise to many fascinating phenomena as diverse as universal conductance fluctuations in mesoscopic metals and speckle patterns in light scattering. Here, the theory of electromagnetic wave propagation in d ...
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Journal ArticlePhysical Review B - Condensed Matter and Materials Physics · January 1, 2000
We consider the contribution of electron-electron interactions to the orbital magnetization of a two-dimensional electron gas, focusing on the ballistic limit in the regime of negligible Landau-level spacing. This regime can be described by combining diagr ...
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Journal ArticleIEEE Transactions on Vehicular Technology · January 1, 1999
A new approach to the modeling of wireless propagation in buildings is introduced. We treat the scattering by walls and local clutter probabilistically through either a relaxation-time approximation in a Boltzmann equation or by using a diffusion equation. ...
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Journal ArticlePhysical Review Letters · January 1, 1999
We develop a semiclassical theory of Coulomb blockade peak heights in quantum dots and show that the dynamics in the dot leads to a large modulation of the peak height. The corrections to the standard statistical theory of peak height distributions, power ...
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Journal ArticlePhysical Review Letters · 1999
Bicrystal grain boundary Josephson junctions of the electron-doped cuprate superconductor Nd1.85Ce0.15CuO4-y are used to measure the temperature dependence of the in-plane London penetration depth λab(T) and the maximum Josephson current Ic(T). Results sho ...
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Journal ArticlePhysical Review Letters · January 1, 1998
We show that the classical dynamics of independent particles can determine the quantum properties of interacting electrons in the ballistic regime. This connection is established using diagrammatic perturbation theory and semiclassical finite-temperature G ...
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Journal ArticlePhysica E: Low-Dimensional Systems and Nanostructures · January 19, 1997
We study interaction effects on the orbital magnetism of diffusive mesoscopic quantum systems. By combining many-body perturbation theory with semiclassical techniques, we show that the interaction contribution to the ensemble-averaged quantum thermodynami ...
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Journal ArticleSuperlattices and Microstructures · January 1, 1997
An asymmetric quantum T wire (QTWR) may be formed whenever two quantum wells (QW) of differing widths intersect. We measured the photoluminescence and photoluminescence excitation from such QTWRs using microscope optics with high spatial resolution. The in ...
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Journal ArticleJournal of Physics A: Mathematical and General · December 1, 1996
We find the invariant measure for two new types of S matrices relevant for chaotic scattering from a cavity in a waveguide. The S matrices considered can be written as a 2 × 2 matrix of blocks, each of rank N, in which the two diagonal blocks are identical ...
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Journal ArticleSurface Science · July 20, 1996
We present a theory of Coulomb blockade oscillations in tunneling through a pair of quantum dots connected by a tunable tunneling junction. The positions and amplitudes of peaks in the linear conductance are directly related, respectively, to the ground st ...
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Journal ArticleEurophysics Letters · February 20, 1996
We propose an information-theoretic model to describe the common features of typical chaotic scattering processes by including two time scales, a prompt and an equilibrated component. The model, introduced in nuclear physics, uses the average value of the ...
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Journal ArticleApplied Physics Letters · December 1, 1995
We study the photocurrent induced in an asymmetric superlattice as a function of the frequency of applied radiation. In order to investigate the principal features, we consider the simplest finite-period structure: one containing an asymmetric unit formed ...
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Journal ArticlePhysica A: Statistical Mechanics and its Applications · October 15, 1995
The statistical properties of the electronic conductance through a ballistic quantum dot are studied by means of an information-theoretic statistical model for the scattering matrix. The model, introduced in the past in the context of nuclear physics, desc ...
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Journal ArticlePhysica D: Nonlinear Phenomena · May 15, 1995
It is shown that classical chaotic scattering has experimentally measurable consequences for the quantum conductance of semiconductor microstructures. These include the existence of conductance fluctuations -a sensitivity of the conductance to either Fermi ...
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Journal Article · February 20, 1995
We propose an information-theoretic statistical model to describe the
universal features of those chaotic scattering processes characterized by a
prompt and an equilibrated component. The model, introduced in the past in
nuclear physics, incorporates the a ...
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Journal Article · 1995
The statistical properties of the electronic conductance through a ballistic quantum dot are studied by means of an information-theoretic statistical model for the scattering matrix. The model, introduced in the past in the context of nuclear physics, desc ...
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Journal ArticleApplied Physics Letters · January 1, 1995
We suggest that a scanning tunneling microscope (STM) may be used for investigating the insulator-conductor interface, in particular SiO2/Si, at nanometer scale. For an insulating film transparent to tunneling, we estimate, using a simple model, the roughn ...
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Journal ArticleChaos (Woodbury, N.Y.) · October 1993
We show that classical chaotic scattering has experimentally measurable consequences for the quantum conductance of semiconductor microstructures. These include the existence of conductance fluctuations-a sensitivity of the conductance to either Fermi ener ...
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Journal ArticleApplied Physics Letters · January 1, 1992
We report the first observation of a quantum bound state formed at the junction of two intersecting quantum wells in the shape of a T. The atomically precise T junctions are fabricated by a novel cleaved edge overgrowth process in the AlGaAs/GaAs system. T ...
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Journal ArticleSuperlattices and Microstructures · January 1, 1991
The quantized conductance of ballistic electrons in narrow constrictions requires the low scattering rates of a high mobility 2-dimensional electron gas(2DEG). Despite the spectacular mobilities of 2DEGs, quantization breaks down for constrictions longer t ...
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Journal ArticleTechnical Digest - International Electron Devices Meeting · December 1, 1990
The charge distributions in the quantum wells of several double barrier diodes were measured. It is found that the ratio of the stored charge to the current is not equal to the coherent state lifetime and is basically insensitive to the amount of scatterin ...
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Journal ArticleSurface Science · April 2, 1990
We calculate the Hall resistance of four-probe junctions with unusual geometries similar to those used in recent experiments. We find a variety of behavior, including quenching at low magnetic fields and a negative Hall resistance at low fields. Our result ...
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Journal ArticleJournal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena · November 1, 1989
Recently, there has been growing interest in exploring the limits to scaling of semiconductor devices, and in understanding their characteristics in the regime where quantum effects and ballistic transport dominate. Using high-resolution fabricatio ...
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Journal ArticleApplied Physics Letters · January 1, 1987
Using Monte Carlo simulation, we show that ballistic electrons coupled with intervalley scattering produce peaks in the distribution function of electrons in submicron structures. The distribution functions f(v,x) and f(ε,x) for a submicron N+-N--N+ GaAs s ...
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Journal ArticleApplied Physics Letters · December 1, 1986
We present results for the negative differential mobility and the distribution function in GaAs and InP for electric fields less than 40 kV/cm based on the analytic solution of the Boltzmann equation for a model with two valleys and three relaxation times. ...
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Journal ArticlePhysica B+C · January 1, 1985
We have solved the Boltzman equation for a submicron N+-N--N+ GaAs structure within a two-valley model using energy-dependent relaxation times. Ballistic electrons produce a large peak in the velocity-distribution function throughout much of the N- region. ...
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Journal ArticlePhysical Review B · January 1, 1984
For a simple submicron semiconductor structure we have calculated exactly the electron distribution f(v,x) within a relaxation-to-local-equilibrium assumption for the collision term of the Boltzmann equation. This is the first calculation of the electron d ...
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Journal ArticleNuclear Instruments and Methods · May 1, 1979
Recent experiments at Brookhaven National Laboratory and Harvard University demonstrate that a detectable sonic signal is produced by energetic proton beams while traversing a fluid medium. The observed acoustic wave agrees with the predictions of a therma ...
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Journal ArticleIEEE Transactions on Nuclear Science · 1977
This work establishes that a detectable sonic signal is produced by protons while traversing through or stopping in a fluid medium. Experiments exploring the global characteristics of both the acoustic generation mechanism and the radiation pattern perform ...
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