School of Physical Sciences, National Institute of Science Education & Research, HBNI, Jatni, 752050, India.
Sci Rep. 2017 Jul 31;7(1):6954. doi: 10.1038/s41598-017-06820-w.
Quantum Hall edge modes are chiral while quantum spin Hall edge modes are helical. However, unlike chiral edge modes which always occur in topological systems, quasi-helical edge modes may arise in a trivial insulator too. These trivial quasi-helical edge modes are not topologically protected and therefore need to be distinguished from helical edge modes arising due to topological reasons. Earlier conductance measurements were used to identify these helical states, in this work we report on the advantage of using the non local shot noise as a probe for the helical nature of these states as also their topological or otherwise origin and compare them with chiral quantum Hall states. We see that in similar set-ups affected by same degree of disorder and inelastic scattering, non local shot noise "HBT" correlations can be positive for helical edge modes but are always negative for the chiral quantum Hall edge modes. Further, while trivial quasi-helical edge modes exhibit negative non-local"HBT" charge correlations, topological helical edge modes can show positive non-local "HBT" charge correlation. We also study the non-local spin correlations and Fano factor for clues as regards both the distinction between chirality/helicity as well as the topological/trivial dichotomy for helical edge modes.
量子霍尔边缘模式是手性的，而量子自旋霍尔边缘模式是螺旋的。然而，与总是出现在拓扑系统中的手性边缘模式不同，准螺旋边缘模式也可能出现在平凡绝缘体中。这些平凡的准螺旋边缘模式不受拓扑保护，因此需要与由于拓扑原因而产生的螺旋边缘模式区分开来。早期的电导测量被用于识别这些螺旋状态，在这项工作中，我们报告了使用非局域散粒噪声作为这些状态的螺旋性质的探针的优势，以及它们的拓扑或其他起源，并将其与手性量子霍尔状态进行了比较。我们发现，在受相同程度无序和非弹性散射影响的类似设置中，非局域散粒噪声“HBT”相关性对于螺旋边缘模式可以是正的，但对于手性量子霍尔边缘模式总是负的。此外，虽然平凡的准螺旋边缘模式表现出负的非局域“HBT”电荷相关性，但拓扑螺旋边缘模式可以表现出正的非局域“HBT”电荷相关性。我们还研究了非局域自旋相关性和费诺因子，以寻找关于手性/螺旋性以及螺旋边缘模式的拓扑/平凡二分法的线索。
