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Multifractal Conductance Fluctuations of Helical Edge States
E B Olshanetsky1,2, G M Gusev3, A D Levin3
1Institute of Semiconductor Physics, Novosibirsk 630090, Russia.
Two-dimensional topological insulators exhibit helical edge states, but exhibit unexpected conductance deviations. This study reveals multifractality in these fluctuations, offering insights into Anderson transitions in topological materials.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Physics
Background:
- Two-dimensional topological insulators possess a bulk band gap and one-dimensional helical edge states.
- Theory predicts topological protection against backscattering for helical transport.
- Experimental observations in long samples show conductance deviations and helical mode localization.
Purpose of the Study:
- Investigate transport properties in HgTe quantum wells with inverted energy spectra.
- Characterize conductance fluctuations in the helical edge state transport regime.
- Explore the multifractality of mesoscopic fluctuations at the spin quantum Hall transition.
Main Methods:
- Experimental transport measurements on HgTe quantum wells.
- Analysis of conductance fluctuations at millikelvin temperatures.
- Study of systems dominated by helical edge state transport.
Main Results:
- Observed multifractality in conductance fluctuations within the helical edge state transport regime.
- Attributed multifractality to mesoscopic fluctuations of electron wave functions or local density of states.
- Demonstrated the HgTe system as a tunable platform for Anderson transition studies.
Conclusions:
- Mesoscopic fluctuations in topological insulators can lead to multifractal conductance patterns.
- The HgTe quantum well system is suitable for studying Anderson transitions between topological states.
- Understanding these fluctuations is crucial for harnessing topological protection in future devices.
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