We report a procedure to determine the frequency-dependent conductance of quantum Hall structures in a broad frequency domain. The procedure is based on the combination of two known probeless methods -- acoustic spectroscopy and microwave spectroscopy. By using the acoustic spectroscopy, we study the low-frequency attenuation and phase shift of a surface acoustic wave in a piezoelectric crystal in the vicinity of the electron (hole) layer. The electronic contribution is resolved using its dependence on a transverse magnetic field. At high frequencies, we study the attenuation of an electromagnetic wave in a coplanar waveguide. To quantitatively calibrate these data, we use the fact that in the quantum-Hall-effect regime the conductance at the maxima of its magnetic field dependence is determined by extended states. Therefore, it should be frequency independent in a broad frequency domain. The procedure is verified by studies of a well-characterized p-SiGe/Ge/SiGe heterostructure.
@article{arxiv.1407.2834,
title = {Contactless Measurement of AC Conductance in Quantum Hall Structures},
author = {I. L. Drichko and A. M. Diakonov and V. A. Malysh and I. Yu. Smirnov and Y. M. Galperin and N. D. Ilyinskaya and A. A. Usikova and M. Kummer and H. von Känel},
journal= {arXiv preprint arXiv:1407.2834},
year = {2015}
}