Quantum spin hall insulator state in HgTe quantum wells
Quantum spin hall insulator state in HgTe quantum wells
复制标题
DOI：
10.1126/science.1148047
复制
发表时间：
2007-11-02
期刊：
影响因子：
56.9
通讯作者：
Zhang, Shou-Cheng
中科院分区：
文献类型：
--
作者：
Koenig, Markus;Wiedmann, Steffen;Zhang, Shou-Cheng
最近的理论预测，量子自旋霍尔效应可能在HgTe/(Hg，Cd)Te量子阱中实现，这是一种存在于零外磁场下的全新的物质量子态。我们制作了这种低密度和高迁移率的样品结构，在这种结构中，我们可以通过外部栅极电压，通过绝缘区将载流子传导从n型调整到p型。对于d<；6.3纳米的薄量子阱，在低温下，绝缘区呈现出小电导消失的常规行为。然而，对于较厚的量子阱(d>；6.3纳米)，名义上的绝缘区域显示出接近2e(2)/h的剩余电导平台，其中e是电子电荷，h是普朗克常数。剩余电导与样品宽度无关，表明它是由边态引起的。此外，在较小的外加磁场作用下，残余电导也被破坏。在临界厚度d=6.3纳米处的量子相变也独立于磁场诱导的绝缘体到金属的相变。这些观测结果为量子自旋霍尔效应提供了实验证据。
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 2e(2)/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.