1] Department of Applied Physics, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
Nat Mater. 2013 Sep;12(9):787-91. doi: 10.1038/nmat3682. Epub 2013 Jun 16.
The quantum spin Hall (QSH) state is a state of matter characterized by a non-trivial topology of its band structure, and associated conducting edge channels. The QSH state was predicted and experimentally demonstrated to be realized in HgTe quantum wells. The existence of the edge channels has been inferred from local and non-local transport measurements in sufficiently small devices. Here we directly confirm the existence of the edge channels by imaging the magnetic fields produced by current flowing in large Hall bars made from HgTe quantum wells. These images distinguish between current that passes through each edge and the bulk. On tuning the bulk conductivity by gating or raising the temperature, we observe a regime in which the edge channels clearly coexist with the conducting bulk, providing input to the question of how ballistic transport may be limited in the edge channels. Our results represent a versatile method for characterization of new QSH materials systems.
量子自旋霍尔(QSH)态是一种物质状态，其能带结构具有非平凡的拓扑结构，并具有相关的传导边缘通道。QSH 态被预测并在 HgTe 量子阱中实验证明得以实现。边缘通道的存在是通过在足够小的器件中进行局域和非局域输运测量推断出来的。在这里，我们通过成像由 HgTe 量子阱制成的大 Hall 条中的电流产生的磁场，直接证实了边缘通道的存在。这些图像区分了通过每个边缘和体的电流。通过门控或提高温度来调节体的电导率，我们观察到一个边缘通道与传导体共存的区域，这为研究弹道输运如何在边缘通道中受到限制提供了线索。我们的结果为新的 QSH 材料系统的特性提供了一种通用的方法。
