Zero-bias Anomaly of Quantum Point Contacts in the Low-Conductance Limit

Y. Ren, W. W. Yu, S. M. Frolov, J. A. Folk, W. Wegscheider

Published 2010-05-20, updated 2010-07-09Version 3

Most quantum point contacts (QPCs) fabricated in high-mobility 2D electron gases show a zero-bias conductance peak near pinchoff, but the origin of this peak remains a mystery. Previous experiments have primarily focused on the zero-bias peak at moderate conductance, in the range (1-2)e^2/h. Here, measurements are presented of zero-bias peaks that persist down to 10^{-4}e^2/h. Magnetic field and temperature dependencies of the zero-bias peak in the low-conductance limit are qualitatively different from the analogous phenomenology at higher conductance, with implications for existing theoretical models of transport in low-density QPCs.