Dependence of the Dresselhaus SOI depending on the quantum ...
Spin-orbit interaction in a dual gated InAs/GaSb quantum well A. Beukman et al. (Kouwenhoven Group) arXiv:1704.03482 Kris Cerveny 19.05.2017 Friday Group Meeting Talk Introduction Motivation:
InAs and GaSb have strong SOI Rashba strength tunable with gating for InAs Control of SOI necessary for spintronic devices Strong SOI + large g-factor + inducible superconductivity ingredients for topological superconducting phase Experiment:
Investigates SOI in dual-gated InAs/GaSb quantum well Tune between single and double carrier regimes ( and + holes) Analyze difference in density of SO split bands Extract zero-field density difference SOI near hybridization gap 2
InAs/GaSb DQW InAs + GaSb Interesting band structure  GaSb valence band maximum higher in energy than InAs conduction band minimum  Energy range where in InAs coexist with holes from the GaSb Strong coupling -hole hybridization gap when  F. Qu et al., PRL 115, (2015)  H. Kroemer, Physica E 20 (2004)
3 Sample 20m x 80m Hall barm x 80m x 80m Hall barm Hall bar 300mK Measurements GaSb substrate lattice matched with subsequent layers no need for thick buffer as with GaAs better coupling between BG and wells!  F. Qu et al., PRL 115, (2015) 4
as function of 2T out of plane magnet High (dashed lines) inside gap Green line separates single- and dual-carrier regimes Line : mobility highest Line : close to hybridization gap 5 Electron-only Regime Trends Clear SdH
in fromoscillations 1-10: beating pattern as function of Extra frequency peak SdH osc. Asymmetry for each spin band periodic between beats in (amplitude and oscillation #)
Trace along line (fixed density) Decreased spacing of peaks (decreasing ) System Increasing favors one#SO ofeigenstate oscillations in A & B nodes pushed to lower B fields
6 Center Frequency Peak Emergent Emergent central central peak peak does does not not correspond correspond to to aa density density
33 possible possible mechanisms mechanisms can can cause cause extra extra freq. freq. components: components: Magnetic Magnetic inter-subband inter-subband scattering scattering Magnetophonon
Magnetophonon resonances resonances Magnetic Magnetic breakdown breakdown: Carriers tunneling between spin polarized Fermi-surfaces [Schematics] W. G. Chambers, Proc. Phys. Soc., Vol 84, 1964 7 Simulation vs Measurement Parameter
tuning yields: and extract Solve for LL energies In 2D systems: Compare data to QM LL simulations with the MB mechanism  Valid for infinite square well =0.04 0 ; = 11.5
Cubic Dresselhaus term set to zero for good fits!?!?  R. Winkler, Spin-orbit Coupling Effects in Two-dimensional Electron and Hole Systems, Springer 2003 8 Two Carrier Regime in InAs present with holes in GaSb simultaneously Investigate influence of hybridization on through magnetoresistance traces on line
Hole concentration increases from point 1 to 13 13: near hybrid. gap 9 Magnetoresistance Data Traces with and without beating no beating no ZFDD extractable Non-monotonic behavior! Band structure calculations agree qualitatively for first 10 points
10 Lack of Beating Two possible reasons: Strong asymmetry between spin species determines visibility ()  When approaching hybrid. gap and are very dissimilar visibility reduced below experimental detection limits Energy window with single spin band present  No beating possible They can not determine which is the cause
 J. Luo et al., PRB, 41, (1990)  F. Nichele et al., ArXiv (2016), 1605.01241 11 Conclusion Study of SOI in InAs/GaSb DQW by top and back gating Tunable in electron-only regime extract Rashba and Dresselhaus Non-monotonic spin splitting behavior in two carriers regime crossing of spin bands due to hybridization 12
Thanks for listening!! 13 =2T 14 15 16 17
Christopher Schierholz Rashba SpinOrbit Interaction in Low and High Magnetic Fields 18
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