Zero-Bias Anomalies in Narrow Tunnel Junctions in the Quantum Hall Regime

We report on the study of cleaved-edge-overgrown line junctions with a serendipitously created narrow opening in an otherwise thin, precise line barrier. Two sets of zero-bias anomalies are observed with an enhanced conductance for filling factors nu > 1 and a strongly suppressed conductance for nu < 1. A transition between the two behaviors is found near nu approximate to 1. The zero-bias anomaly ( ZBA) line shapes find explanation in Luttinger liquid models of tunneling between quantum Hall edge states. The ZBA for nu < 1 occurs from strong backscattering induced by suppression of quasiparticle tunneling between the edge channels for the n = 0 Landau levels. The ZBA for nu > 1 arises from weak tunneling of quasiparticles between the n = 1 edge channels.