RT Journal Article
SR Electronic
T1 Quantum Spin Hall Insulator State in HgTe Quantum Wells
JF Science
JO Science
FD American Association for the Advancement of Science
SP 766
OP 770
DO 10.1126/science.1148047
VO 318
IS 5851
A1 König, Markus
A1 Wiedmann, Steffen
A1 Brüne, Christoph
A1 Roth, Andreas
A1 Buhmann, Hartmut
A1 Molenkamp, Laurens W.
A1 Qi, Xiao-Liang
A1 Zhang, Shou-Cheng
YR 2007
UL http://science.sciencemag.org/content/318/5851/766.abstract
AB 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.