Scholars@Duke
Olivier Delaire

Olivier Delaire

Associate Professor of the Thomas Lord Department of Mechanical Engineering and Materials Science
Thomas Lord Department of Mechanical Engineering and Materials Science
olivier.delaire@duke.edu
387 Gross Hall, Durham, NC 27708
144 Hudson Hall, Box 90300, Durham, NC 27708

Featured Works

Ultrafast lattice disordering can be accelerated by electronic collisional forces

Journal article Nature Physics · October 1, 2023 Featured Publication In the prevalent picture of ultrafast structural phase transitions, atomic motion occurs in a slowly varying potential energy surface adiabatically determined by fast electrons. However, this ignores non-conservative forces caused by electron–lattice colli ... Full text Cite

Nonthermal Bonding Origin of a Novel Photoexcited Lattice Instability in SnSe.

Journal article Physical review letters · October 2023 Featured Publication Lattice dynamics measurements are often crucial tools for understanding how materials transform between different structures. We report time-resolved x-ray scattering-based measurements of the nonequilibrium lattice dynamics in SnSe, a monochalcogenide rep ... Full text Cite

Extreme phonon anharmonicity underpins superionic diffusion and ultralow thermal conductivity in argyrodite Ag<sub>8</sub>SnSe<sub>6</sub>.

Journal article Nature materials · August 2023 Featured Publication Ultralow thermal conductivity and fast ionic diffusion endow superionic materials with excellent performance both as thermoelectric converters and as solid-state electrolytes. Yet the correlation and interdependence between these two features remain unclea ... Full text Cite

Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe3.

Journal article Nature communications · July 2022 Featured Publication Spin and lattice are two fundamental degrees of freedom in a solid, and their fluctuations about the equilibrium values in a magnetic ordered crystalline lattice form quasiparticles termed magnons (spin waves) and phonons (lattice waves), respectively. In ... Full text Cite

Strongly Anharmonic Phonons and Their Role in Superionic Diffusion and Ultralow Thermal Conductivity of Cu7PSe6

Journal article Advanced Energy Materials · June 1, 2022 Featured Publication The quest for advanced superionic materials requires understanding their complex atomic dynamics, but detailed studies of the interplay between lattice vibrations and ionic diffusion remain scarce. Here inelastic and quasielastic neutron scattering measure ... Full text Cite

Direct Detection of V-V Atom Dimerization and Rotation Dynamic Pathways upon Ultrafast Photoexcitation in VO2

Journal article Physical Review X · June 1, 2022 Featured Publication Photoinduced ultrafast phase transitions can generate quasiequilibrium states with novel emergent properties modulated by the interplay of electronic and lattice degrees of freedoms. Therefore, accurately probing transient atomic structures and their dynam ... Full text Cite

Observation of a Novel Lattice Instability in Ultrafast Photoexcited SnSe

Journal article Physical Review X · March 1, 2022 Featured Publication There is growing interest in using ultrafast light pulses to drive functional materials into nonequilibrium states with novel properties. The conventional wisdom is that above-gap photoexcitation behaves similarly to raising the electronic temperature and ... Full text Cite

A two-dimensional type I superionic conductor.

Journal article Nature materials · December 2021 Featured Publication Superionic conductors possess liquid-like ionic diffusivity in the solid state, finding wide applicability from electrolytes in energy storage to materials for thermoelectric energy conversion. Type I superionic conductors (for example, AgI, Ag2 ... Full text Cite

Fast Na diffusion and anharmonic phonon dynamics in superionic Na3PS4

Journal article Energy and Environmental Science · December 1, 2021 Featured Publication The design of new solid electrolytes (SEs) hinges on identifying and tuning relevant descriptors. Phonons describe the atomic dynamics in crystalline materials and provide a basis to encode possible minimum energy pathways for ion migration, but anharmonic ... Full text Cite

Two-dimensional overdamped fluctuations of the soft perovskite lattice in CsPbBr3.

Journal article Nat Mater · July 2021 Featured Publication Lead halide perovskites exhibit structural instabilities and large atomic fluctuations thought to impact their optical and thermal properties, yet detailed structural and temporal correlations of their atomic motions remain poorly understood. Here, these c ... Full text Link to item Cite

Soft anharmonic phonons and ultralow thermal conductivity in Mg3(Sb, Bi)2 thermoelectrics.

Journal article Science advances · May 2021 Featured Publication The candidate thermoelectric compounds Mg3Sb2 and Mg3Bi2 show excellent performance near ambient temperature, enabled by an anomalously low lattice thermal conductivity (κl) comparable to those of much ... Full text Cite

Controlling phonon lifetimes via sublattice disordering in AgBiSe2

Journal article Physical Review Materials · October 12, 2020 Featured Publication Understanding and controlling microscopic heat transfer mechanisms in solids is critical to material design in numerous technological applications. Yet, the current understanding of thermal transport in semiconductors and insulators is limited by the diffi ... Full text Cite

Extended anharmonic collapse of phonon dispersions in SnS and SnSe

Journal article Nature Communications · September 4, 2020 Featured Publication AbstractThe lattice dynamics and high-temperature structural transition in SnS and SnSe are investigated via inelastic neutron scattering, high-resolution Raman spectroscopy and anharmonic first-principles simulations. We u ... Full text Cite

Anharmonic lattice dynamics and superionic transition in AgCrSe 2

Journal article Proceedings of the National Academy of Sciences · February 25, 2020 Featured Publication Significance Unveiling the unusual atomic dynamics in superionic conductors is critical for the design of energy conversion and storage materials, for example to rationalize their ther ... Full text Open Access Cite

Lattice dynamics of the hybrid improper ferroelectrics (Ca,Sr)3Ti2 O7

Journal article Physical Review B · December 6, 2019 Featured Publication The structure and lattice dynamics of the hybrid improper ferroelectric compound Ca3-xSrxTi2O7 (for x=0,0.6, and 0.9) have been studied with a combination of diffraction, inelastic scattering experiments, Raman spectroscopy, and calorimetry measurements, a ... Full text Cite

Frustrated Magnetism in Mott Insulating (V1-xCrx)2 O3

Journal article Physical Review X · February 21, 2019 Featured Publication V2O3 famously features all four combinations of paramagnetic versus antiferromagnetic and metallic versus insulating states of matter in response to percent-level doping, pressure in the GPa range, and temperature below 300 K. Using time-of-flight neutron ... Full text Cite

Selective breakdown of phonon quasiparticles across superionic transition in CuCrSe 2

Journal article Nature Physics · January 1, 2019 Featured Publication Superionic crystals exhibit ionic mobilities comparable to liquids while maintaining a periodic crystalline lattice. The atomic dynamics leading to large ionic mobility have long been debated. A central question is whether phonon quasiparticles—which condu ... Full text Open Access Cite

Momentum-resolved observations of the phonon instability driving geometric improper ferroelectricity in yttrium manganite

Journal article Nature Communications · December 1, 2018 Featured Publication Magnetoelectrics offer tantalizing opportunities for devices coupling ferroelectricity and magnetism but remain difficult to realize. Breakthrough strategies could circumvent the mutually exclusive origins of magnetism and ferroelectricity by exploiting th ... Full text Open Access Cite

Ultrafast disordering of vanadium dimers in photoexcited VO 2

Journal article Science · November 2, 2018 Featured Publication Snapshots of a phase transition Time-resolved x-ray scattering can be used to investigate the dynamics of materials during the switch from one structural phase to another. So far, methods provide an e ... Full text Cite

Recent progresses on physics and applications of vanadium dioxide

Journal article Materials Today · October 1, 2018 Featured Publication As a strongly correlated electron material, vanadium dioxide (VO2) has been a focus of research since its discovery in 1959, owing to its well-known metal–insulator transition coupled with a structural phase transition. Recent years have witness ... Full text Cite

Mobility and stability descriptors of lithium ion conductors based on lattice dynamics

Conference ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY · March 18, 2018 Featured Publication Link to item Cite

Neutron and x-ray scattering study of phonon dispersion and diffuse scattering in (Na,Bi)Ti O3-xBaTi O3 single crystals near the morphotropic phase boundary

Journal article Physical Review B · November 10, 2017 Featured Publication Neutron and x-ray scattering measurements were performed on (Na1/2Bi1/2)TiO3-xat%BaTiO3 (NBT-xBT) single crystals (x=4, 5, 6.5, and 7.5) across the morphotropic phase boundary (MPB), as a function of both composition and temperature, and probing both struc ... Full text Cite

Lattice dynamics and thermal transport in multiferroic CuCrO2

Journal article Physical Review B · February 9, 2017 Featured Publication Inelastic neutron and x-ray scattering measurements of phonons and spin waves were performed in the delafossite compound CuCrO2 over a wide range of temperature, and complemented with first-principles lattice dynamics simulations. The phonon dispersions an ... Full text Cite

Anomalously low electronic thermal conductivity in metallic vanadium dioxide.

Journal article Science (New York, N.Y.) · January 2017 Featured Publication In electrically conductive solids, the Wiedemann-Franz law requires the electronic contribution to thermal conductivity to be proportional to electrical conductivity. Violations of the Wiedemann-Franz law are typically an indication of unconventional quasi ... Full text Cite

Hierarchical optimization for neutron scattering problems

Journal article Journal of Computational Physics · June 15, 2016 Featured Publication We present a scalable optimization method for neutron scattering problems that determines confidence regions of simulation parameters in lattice dynamics models used to fit neutron scattering data for crystalline solids. The method uses physics-based hiera ... Full text Link to item Cite

Hierarchical domain structure of lead-free piezoelectric (Na1/2 Bi1/2)TiO3-(K1/2 Bi1/2)TiO3 single crystals

Journal article Journal of Applied Physics · May 4, 2016 Featured Publication Full text Cite

Structural phase transition and phonon instability in Cu12Sb4S13

Journal article Physical Review B · February 2016 Featured Publication A structural phase transition has been discovered in the synthetic tetrahedrite Cu12Sb4S13 at approximately 88 K. Upon cooling, the material transforms from its known cubic symmetry to a tetragonal unit cell that is characterized by an in-plane ordering th ... Full text Cite

Electron-phonon coupling and thermal transport in the thermoelectric compound Mo3Sb(7−x)Te(x)

Journal article Physical Review B · December 2015 Featured Publication Phonon properties of Mo3Sb(7−x)Te(x) (x=0,1.5,1.7), a potential high-temperature thermoelectric material, have been studied with inelastic neutron and x-ray scattering, and with first-principles simulations. The substitution of Te for Sb leads to pronounce ... Full text Open Access Link to item Cite

Orbitally driven giant phonon anharmonicity in SnSe

Journal article Nature Physics · December 1, 2015 Featured Publication Understanding elementary excitations and their couplings in condensed matter systems is critical for developing better energy-conversion devices. In thermoelectric materials, the heat-to-electricity conversion efficiency is directly improved by suppressing ... Full text Cite

Twisting phonons in complex crystals with quasi-one-dimensional substructures.

Journal article Nature communications · April 2015 Featured Publication A variety of crystals contain quasi-one-dimensional substructures, which yield distinctive electronic, spintronic, optical and thermoelectric properties. There is a lack of understanding of the lattice dynamics that influences the properties of such comple ... Full text Cite

Metallization of vanadium dioxide driven by large phonon entropy.

Journal article Nature · November 2014 Featured Publication Phase competition underlies many remarkable and technologically important phenomena in transition metal oxides. Vanadium dioxide (VO2) exhibits a first-order metal-insulator transition (MIT) near room temperature, where conductivity is suppressed and the l ... Full text Cite

Phonon self-energy and origin of anomalous neutron scattering spectra in SnTe and PbTe thermoelectrics.

Journal article Physical review letters · May 2014 Featured Publication The anharmonic lattice dynamics of rock-salt thermoelectric compounds SnTe and PbTe are investigated with inelastic neutron scattering (INS) and first-principles calculations. The experiments show that, surprisingly, although SnTe is closer to the ferroele ... Full text Cite

Phonon localization drives polar nanoregions in a relaxor ferroelectric.

Journal article Nature communications · April 2014 Featured Publication Relaxor ferroelectrics exemplify a class of functional materials where interplay between disorder and phase instability results in inhomogeneous nanoregions. Although known for about 30 years, there is no definitive explanation for polar nanoregions (PNRs) ... Full text Cite

Glass-like phonon scattering from a spontaneous nanostructure in AgSbTe2.

Journal article Nature nanotechnology · June 2013 Featured Publication Materials with very low thermal conductivity are of great interest for both thermoelectric and optical phase-change applications. Synthetic nanostructuring is most promising for suppressing thermal conductivity through phonon scattering, but challenges rem ... Full text Cite

Anharmonic phonons and magnons in BiFeO 3

Journal article Physical Review B Condensed Matter and Materials Physics · February 13, 2012 Featured Publication The phonon density of states (DOS) and magnetic excitation spectrum of polycrystalline BiFeO 3 were measured for temperatures 200≤T≤750K, using inelastic neutron scattering (INS). Our results indicate that the magnetic spectrum of BiFeO 3 Full text Cite

Giant anharmonic phonon scattering in PbTe.

Journal article Nature materials · June 2011 Featured Publication Understanding the microscopic processes affecting the bulk thermal conductivity is crucial to develop more efficient thermoelectric materials. PbTe is currently one of the leading thermoelectric materials, largely thanks to its low thermal conductivity. Ho ... Full text Cite

Phonon softening and metallization of a narrow-gap semiconductor by thermal disorder

Journal article Proceedings of the National Academy of Sciences of the United States of America · March 22, 2011 Featured Publication The vibrations of ions in solids at finite temperature depend on interatomic force-constants that result from electrostatic interactions between ions, and the response of the electron density to atomic displacements. At high temperatures, vibration amplitu ... Full text Cite

Temperature and pressure dependence of the Fe-specific phonon density of states in Ba ( Fe1-x Cox)2As2

Journal article Physical Review B Condensed Matter and Materials Physics · March 4, 2010 Featured Publication The 57Fe -specific phonon density of states (DOS) of Ba (Fe 1-x Cox)2 As2 single crystals (x=0.0,0.08) was measured at cryogenic temperatures and at high pressures with nuclear-resonant inelastic x-ray ... Full text Cite

Phonon density of states of LaFeAsO(1-x)Fx.

Journal article Physical review letters · October 2008 Featured Publication We have studied the phonon density of states (PDOS) in LaFeAsO(1-x)Fx with inelastic neutron scattering methods. The PDOS of the parent compound (x=0) is very similar to the PDOS of samples optimally doped with fluorine to achieve the maximum Tc (x approxi ... Full text Cite

Adiabatic electron-phonon interaction and high-temperature thermodynamics of A15 compounds.

Journal article Physical review letters · September 2008 Featured Publication Inelastic neutron scattering was used to measure the phonon densities of states of the A15 compounds V3Si, V3Ge, and V3Co at temperatures from 10 to 1,273 K. It was found that phonons in V3Si and V3Ge, which are superconducting at low temperatures, exhibit ... Full text Cite

Charge redistribution and phonon entropy of vanadium alloys.

Journal article Physical review letters · December 2006 Featured Publication The effects of alloying on the lattice dynamics of vanadium were investigated using inelastic neutron scattering. Phonon densities of states were obtained for bcc solid solutions of V with 3d, 4d, and 5d transition metal solutes, from which vibrational ent ... Full text Cite

Vibrations of micro-eV energies in nanocrystalline microstructures.

Journal article Physical review letters · November 2004 Featured Publication The phonon density of states of nanocrystalline bcc Fe and nanocrystalline fcc Ni3Fe were measured by inelastic neutron scattering in two different ranges of energy. As has been reported previously, the nanocrystalline materials showed enhancements in thei ... Full text Cite

Negative entropy of mixing for vanadium-platinum solutions.

Journal article Physical review letters · October 2004 Featured Publication The phonon densities of states for pure vanadium and the solid solutions V-6.25% Ni, Pd, Pt were determined from inelastic neutron scattering measurements. The solute atoms caused a large stiffening of the phonons, resulting in large, negative vibrational ... Full text Cite