Quantum Spin Hall Insulator State in HgTe Quantum Wells

Abstract

Recent theory predicted that the Quantum Spin Hall Effect, a fundamentally novel quantum state of matter that exists at zero external magnetic field, may be realized in HgTe/(Hg,Cd)Te quantum wells. We have fabricated such sample structures with low density and high mobility in which we can tune, through an external gate voltage, the carrier conduction from n-type to the p-type, passing through an insulating regime. For thin quantum wells with well width d < 6.3 nm, the insulating regime shows the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d > 6.3 nm), the nominally insulating regime shows a plateau of residual conductance close to 2e 2 /h. The residual conductance is independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance is destroyed by a small external magnetic field.

Interface engineering of quantum Hall effects in digital transition metal oxide heterostructures

“…The direct confirmation of the TI state is possible by measuring the conductance. As in Bernevig et al 5 and König et al 8 , the conductance should be quantized as  = 2e 2 /h per (111) bilayer in the two-terminal measurement. The conductance can be controlled by using the gate voltage.…”

Magnetoresistance Anomaly in Topological Kondo Insulator SmB6 Nanowires with Strong Surface Magnetism

“…Many intriguing phenomena such as weak anti‐localization, quantum spin, and anomalous Hall effect have been discovered in TIs 3, 4, 5, 6. The interplay between TIs and magnetism or superconductivity can even lead to the possible realization of magnetic monopoles7 or Majorana fermions 8.…”

Room Temperature Quantum Spin Hall Insulators with a Buckled Square Lattice

“…Topological insulators (TIs), [1][2][3][4][5][6][7] as a new class of quantum materials, hold great potential for applications in quantum information, spintronics, field effect transistors, as well as thermoelectrics. [8][9][10][11][12][13][14] The most interesting character of TIs is the presence of robust topological Dirac surface states in three-dimensional (3D) TIs or helical edge states in two-dimensional (2D) TIs with spin locked to momentum as protected by time-reversal symmetry.…”

“…6,7 There is great interest in searching for room temperature (RT) 2D TIs. Among all predicted or synthesized 2D TIs, the hexagonal honeycomb lattice is the most common motif.…”