Tunneling measurements of the coulomb pseudogap in a two-dimensional electron system in a quantizing magnetic field

Abstract

We study the Coulomb pseudogap for tunneling into the two-dimensional electron system of high-mobility (Al,Ga)As/GaAs heterojunctions subjected to a quantizing magnetic field at filling factor $ν\leq 1$. Tunnel current-voltage characteristics show that for the double maximum observed in the tunnel resistance at $ν\approx 1$ the pseudogap is linear in energy with a slope that depends on filling factor, magnetic field, and temperature. We give a qualitative account of the filling factor dependence of the pseudogap slope and we confirm the recently reported appearance of another relaxation time for tunneling at $ν\approx 1$. For the tunnel resistance peaks at $ν=1/3$ and 2/3 a completely different behaviour of the current-voltage curves is found and interpreted as manifestation of the fractional gap.

7 pages, 9 figures included. Accepted to PRB