Lundi 10 février 2014 à 10h15
Salle 234, Ecole de Physique

Edge reconstruction in fractional quantum Hall effect and quantum spin Hall effect

Jianhui Wang, Weizmann Institute, Israel

In the first half of my talk I will discuss edge reconstruction in fractional quantum Hall effect, using the state at filling factor 2/3 as an example. By edge reconstruction we mean the appearance of an additional incompressible strip outside the minimum edge structure when the confining potential is smooth. I will explain how this combined with interaction and disorder provides a unified theory for some recent experimental results, namely a plateau at a transmission of 1/2 through a quantum point contact and a crossover of the effective charge from e/3 at high temperature to 2e/3 at low temperature. In the second half of my talk I will discuss the edge structure of quantum spin Hall effect (more specifically the Bernevig-Zhang model) when interaction and smoothness of the confining potential are taken into account. I will show that time-reversal symmetry can be broken at the edge via spontaneous spin polarization. More complicated structures are also possible when the confining potential become even smoother. Experimental implications will be discussed.