Zero-bias tunneling anomaly in a two-dimensional electron system with disorder

Abstract

The temperature dependence of a zero-bias anomaly in the tunneling conductance of an Al/δ-GaAs tunneling structure with a two-dimensional electron density in the δ-layer of 3.5 × 1012 cm−2 has been investigated. It has been shown that the respective drop Δρ(ɛ, T) in the tunneling density of states ρ near the Fermi level EF of the two-dimensional electron system depends logarithmically on the energy ɛ within the range of 2.7kT < |ɛ| < ħ/τ, where ɛ is measured with respect to EF and τ is the momentum relaxation time of two-dimensional electrons. It has been found that the drop depth Δρ(0, T)/ρ is also proportional to ln(kT/ɛ0) in the temperature range T = 0.1–20 K and saturates below 0.1 K.