Activation energies and localization in the fractional quantum Hall effect


Journal Article

This paper summarizes an extensive study of the temperature dependence of magnetotransport in the fractional quantum Hall effect in GaAs-AlxGa1-xAs heterostructure devices of varying mobility and density. For devices with electron mobility 400 000 1 000 000 cm2/V s, we find a single activation energy, /23, in the longitudinal transport coefficients, xx and xx, for Landau-level filling factors=(1/3, (2/3, (4/3, and (5/3, with a magnetic field dependence which is vanishingly small for B 5.5 T and increases to 63.8 K at B=30 T. The observed 3 is smaller by more than a factor of 3 than either the unbound quasiparticle-quasihole pair-creation energy gap or the magneto-roton energy gap, calculated for an ideal two-dimensional electron system. Observations for devices of mobility 0 300 000 cm2/V s yield even smaller 3. Adequate fitting of all our results requires inclusion of finite electron layer thickness and disorder, with the effect of decreasing the energy gaps and providing a finite magnetic field threshold. At low temperatures and high magnetic fields, deviations from activated conduction are observed. These deviations are attributed to two-dimensional hopping conduction in a magnetic field. Samples of sufficiently low mobility, 0150 000 cm2/V s exhibit no evidence of activated conduction. Rather, the transport is qualitatively consistent with two-dimensional hopping alone. Studies at Landau-level filling factors =(2/5 and (3/5 also yield a single activation energy, /25, with a weak magnetic field dependence. Experimentally, we find 35 0.4, compared with an expected ratio of 0.28 from simple theoretical considerations. © 1987 The American Physical Society.

Full Text

Duke Authors

Cited Authors

  • Boebinger, GS; Stormer, HL; Tsui, DC; Chang, AM; Hwang, JCM; Cho, AY; Tu, CW; Weimann, G

Published Date

  • January 1, 1987

Published In

Volume / Issue

  • 36 / 15

Start / End Page

  • 7919 - 7929

International Standard Serial Number (ISSN)

  • 0163-1829

Digital Object Identifier (DOI)

  • 10.1103/PhysRevB.36.7919

Citation Source

  • Scopus