Challenges to the textbook picture in 2D-topological insulator materials investigated by novel local probes
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Challenges to the textbook picture in 2D-topological insulator materials investigated by novel local probes
CIC nanoGUNE Seminars
- Speaker
-
M. Reyes-Calvo, Nanoimaging Group nanoGUNE / Stanford University
- When
-
2015/02/23
12:00
- Place
- nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian
- Add to calendar
-
iCal
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In the Quantum Spin Hall textbook picture, a 2-dimensional topologically non-
trivial insulator _(2d-TI)_ is expected to present conductive edge states
protected against backscattering. The application of a magnetic field should
lift this protection, and above a critical field the material would enter a
trivial insulator regime, where the edge conduction fully disappears.
In real 2d-TI materials, such as inverted HgTe quantum wells, however, the
picture seems to be more complex and scattering happens over long enough
distances (around microns). Furthermore, although the resistance of the
devices increases in the presence of a magnetic field, but some predictions,
such as the removal of the edge conduction have not been yet directly probed.
In our work, we use novel local probe techniques to shed some light into the
above challenges. On the one hand, Scanning Gate Microscopy results allow us
to identify the microscopic origin of scattering in the quantum spin hall edge
states. On the other hand, Microwave Impedance Microscopy results reveal that
edge conduction persists unexpectedly at high magnetic fields. Finally, we
propose the use of lateral heterojunctions to probe the nature of such
unexpected states.