Signatures of neutral quantum Hall modes in transport through low-density

Bernd Rosenow

Harvard University, USA

Constrictions in fractional quantum Hall (FQH) systems not only facilitate backscattering between counter-propagating edge modes, but also reduce the constriction filling fraction $\nu_c$ with respect to the bulk filling fraction $\nu_b$. If both $\nu_b$ and $\nu_c$ correspond to incompressible FQH states, at least part of the constriction region is surrounded by composite edges, whose low energy dynamics is characterized by a charge mode and one or several neutral modes. The FQH neutral modes influence charge transport through the constriction in important ways. In the limit of coherent transport, the presence of neutral modes gives rise to universal conductance fluctuations. In the incoherent regime, when the thermal length is smaller than the geometric size of the constriction, neutral modes renormalize the strength of scattering across the constriction, and thus determine the relative strength of forward and backwards scattering.