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Magnetic-field-induced localization in 2D topological insulators.
Pierre Delplace1, Jian Li, Markus Büttiker
1Département de Physique Théorique, Université de Genève, CH-1211 Genève, Switzerland.
Physical Review Letters
|February 2, 2013
Summary
Localized helical edge states in quantum spin Hall insulators are achieved by breaking time-reversal symmetry with a magnetic field. Our model shows localization length depends on magnetic field strength, decreasing with B^{-2} at low fields and saturating at high fields.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Helical edge states in quantum spin Hall insulators are crucial for spintronic applications.
- Localization of these states is necessary for device functionality.
- Time-reversal invariance must be broken to induce localization.
Purpose of the Study:
- To develop a theoretical model for the localization of helical edge states.
- To investigate the role of random magnetic fluxes in this localization process.
- To determine the dependence of localization length on applied magnetic field.
Main Methods:
- Development of a scattering theory model.
- Analysis of helical edge state coupling to random magnetic fluxes.
- Theoretical calculation of localization length as a function of magnetic field.
Main Results:
- The localization length is inversely proportional to the square of a small magnetic field (B^{-2}).
- The localization length saturates to a constant value at sufficiently large magnetic fields.
- Specific estimations for HgTe/CdTe quantum wells are provided.
Conclusions:
- Random magnetic fluxes provide a mechanism for localizing helical edge states.
- The magnetic field dependence of localization length offers a tunable parameter for controlling edge state behavior.
- The findings are relevant for designing spintronic devices based on quantum spin Hall insulators.
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