Wigner glass formation in 2DHG of p-Si/SiGe by high magnetic fields

Abstract

High-frequency ac σx xac = σ 1 — i · σ2 and dc σxxdc conductivities were studied on a low density (p = 8.2 . 1010 cm-2) 2DHG of p-Si/Si0.92Ge0.08 heterostructures by acoustic and transport techniques respectively. In the vicinity of B=3.5 T the integer quantum Hall effect related to the filling factor ν = 1 was observed and at low temperatures the ac conductance corresponds to hopping of the holes between localized states: σ2 > σ 1 > 0. The features revealed in the ultraquantum limit B>14 T at low temperatures T<0.8 K: (i) negative value of σ2; (ii) small imaginary part of the ac conductance σ1 >> |σ2|; (iii) linear frequency dependence of σ1 and σ2; (iv) independence of σ1 and σ2 on the magnetic field and temperature; (v) thresholdlike behavior of the I-V curves and (vi) its hysteresis; (vii) I-V dependence in the sub-threshold region typical for a creep in a crystal I ∼ exp(—A/V 0.3) indicate the formation of a pinned Wigner glass.