Quantum Spin Hall Insulator State in HgTe Quantum Wells

By M. König, S. Wiedmann, C. Brüne, A. Roth, H. Buhmann, L. Molenkamp, Xiao-Liang Qi, Shoucheng Zhang. Science, 2007

4,748 citations recorded by the source corpus.

Recent theory predicted that the quantum spin Hall effect, a fundamentally new quantum state of matter that exists at zero external magnetic field, may be realized in HgTe/(Hg,Cd)Te quantum wells. We fabricated such sample structures with low density and high mobility in which we could tune, through an external gate voltage, the carrier conduction from n-type to p-type, passing through an insulating regime. For thin quantum wells with well width d < 6.3 nanometers, the insulating regime showed the conventional behavior of vanishingly small conductance at low temperature. However, for thicker quantum wells (d > 6.3 nanometers), the nominally insulating regime showed a plateau of residual conductance close to 2e2/h, where e is the electron charge and h is Planck's constant. The residual conductance was independent of the sample width, indicating that it is caused by edge states. Furthermore, the residual conductance was destroyed by a small external magnetic field. The quantum phase transition at the critical thickness, d = 6.3 nanometers, was also independently determined from the magnetic field–induced insulator-to-metal transition. These observations provide experimental evidence of the quantum spin Hall effect.

Subfields: Atomic and Molecular Physics, and Optics, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/a38e5bfdbbd8e204c42b6180f041231fb935a3ad

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In Atomic and Molecular Physics, and Optics

In Materials Chemistry

Citations in the corpus

Heusler Compounds—A Material Class With Exceptional Properties (2011, background): “Recently, it was demonstrated that around 50 Heusler compounds show a band inversion, similar to that of HgTe, in which the quantum spin Hall effect was observed experimentally [11], [12], [ 113 ].”
Photonic topological insulators. (2012, background): “Although success in identifying topological insulator behavior among strongly spin-orbit coupled electronic systems has been impressive [ 8, 9, 10, 11], the property is still relatively uncommon.”