Compressibility of the quantum spin Hall insulator HgTe
POSTER
Abstract
Quantum spin Hall (QSH) insulators are two-dimensional electron systems which host spin-polarized edge states while the bulk remains insulating. These helical edge states provide a potential support system to encode information in ‘topological quantum bits’ robust to the decoherence. Despite immense theoretical and experimental efforts, the rise of these new materials has however been hampered by strong difficulties to clearly observe their predicted topological properties. These challenges motivate the investigation of the dynamics of their topological edge states using microwave techniques.
Here we report on the compressibility of the QSH insulator HgTe, measured in metal-oxyde-HgTe capacitors. The quantum capacitance reflects the expected band structure of the HgTe quantum wells. A capacitance minimum associated to a resistance maximum signal the QSH regime. We analyse the dependence of this minimum as a function of the capacitor size and identify both 2D and 1D contributions, which can be used to estimate the 1D channel size. Similar measurements performed on non-topological quantum wells do not show any sizable 1D contributions in agreement with the absence of edge states.
Here we report on the compressibility of the QSH insulator HgTe, measured in metal-oxyde-HgTe capacitors. The quantum capacitance reflects the expected band structure of the HgTe quantum wells. A capacitance minimum associated to a resistance maximum signal the QSH regime. We analyse the dependence of this minimum as a function of the capacitor size and identify both 2D and 1D contributions, which can be used to estimate the 1D channel size. Similar measurements performed on non-topological quantum wells do not show any sizable 1D contributions in agreement with the absence of edge states.
*We acknowledge support from the ERC StG Castles (Grant 758077)
Presenters
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Matthieu Dartiailh
- Physics, New York University
- Center for Quantum Phenomena, Department of Physics, New York University
- Laboratoire Pierre Aigrain UMR 8551, Ecole normale Supérieure - PSL Research university, CNRS, Université Pierre et Marie Curie - Sorbonne Universités, Université Paris Dider