We argue that it is hopping transport that is responsible for broadening of the σxx peaks in low-mobility samples. Explicit expressions for the width Δν of a peak as a function of the temperature T, current J, and frequency ω are found. It is shown that Δv grows with T as ( T T1)K, where k is the inverse localization-length exponent. The current J is shown to act like an effective temperature Teff(J) α J 1 2 if Teff(J) ≫ T. Broadening of the oh peaks with frequency ω is found to be determined by the effective temperature Teff(ω) ≈ ℏω kB.
Bibliographical noteFunding Information:
We are grateful to L.W. Engel, SW. Hwang, C. Kurdak, D. Shahar, D.C. Tsui and H.P. Wei for providing us with the experimental data [22,26]T. his work was supportedb y the National Science Foundation under Grant No. DMR-9020587.