Abstract:
Topological insulators (TI) have been the subject of intense theoretical and experimental investigation due to their distinct electronic properties compared to conventional electronic systems. This thesis investigates electronic properties of two topological insulators, InAs/GaSb double quantum wells and monolayer WTe2, through transport measurements at ultra-low temperatures.
Using double gate geometry, InAs/GaSb quantum wells can be tuned between topological and trivial states. Previous works have reported the existence of robust helical edge conduction in the inverted regime. Here, we found an enhanced edge conduction in the trivial state with superficial similarity to the observed edge conduction in those reports. However, using various transport techniques and sample geometries, the edge conduction in our samples was found to have a non-helical origin.
Another topological insulator that is studied in this thesis is monolayer WTe2. Here, we report that monolayer WTe2, already known to be a 2D TI, becomes a superconductor by mild electrostatic doping, at temperatures below 1K. The 2D TI-superconductor transition can be easily driven by applying a small gate voltage. Furthermore, we observed peculiar features such as enhancement of parallel critical magnetic field above the Pauli limit possibly, from spin orbit scattering.
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2020-03-02T12:30:002020-03-02T14:30:00"Quantum Transport in 2D Topological Insulators"Event Information:
Final PhD Oral Examination
Abstract:
Topological insulators (TI) have been the subject of intense theoretical and experimental investigation due to their distinct electronic properties compared to conventional electronic systems. This thesis investigates electronic properties of two topological insulators, InAs/GaSb double quantum wells and monolayer WTe2, through transport measurements at ultra-low temperatures.
Using double gate geometry, InAs/GaSb quantum wells can be tuned between topological and trivial states. Previous works have reported the existence of robust helical edge conduction in the inverted regime. Here, we found an enhanced edge conduction in the trivial state with superficial similarity to the observed edge conduction in those reports. However, using various transport techniques and sample geometries, the edge conduction in our samples was found to have a non-helical origin.
Another topological insulator that is studied in this thesis is monolayer WTe2. Here, we report that monolayer WTe2, already known to be a 2D TI, becomes a superconductor by mild electrostatic doping, at temperatures below 1K. The 2D TI-superconductor transition can be easily driven by applying a small gate voltage. Furthermore, we observed peculiar features such as enhancement of parallel critical magnetic field above the Pauli limit possibly, from spin orbit scattering.Event Location:
Room 200, Graduate Student Centre (6371 Crescent Road)