Non-linear transport in quantum Hall systems

Michael Zudov

University of Minnesota, USA

When a two-dimensional electron system (2DES) is subject to microwave radiation, its magnetoresistance exhibits microwave-induced resistance oscillations (MIRO) originating from inter-Landau level transitions due to microwave absorption. Another class of oscillations appears in 2DES at elevated temperatures when acoustic phonons become excited. Remarkably, even though phonons of all different energies below the thermal energy are present, the main contribution comes from the most energetic phonons an electron can scatter off. The frequency of such phonon is determined only by the sound velocity and electron momentum. As a result, absorption of such phonons leads to indirect inter-Landau level transitions and 2DES shows phonon-induced resistance oscillations (PIRO). Here we focus on the extension of MIRO and PIRO into non-linear transport regime which is known for Hall-field induced resistance oscillations (HIRO) arising from elastic transitions between Hall field-tilted Landau levels. Non-linear regime in microwave-illuminated 2DES [1] reveals many unexpected features, e.g. the evolution of the MIRO peaks into zero-differential resistance states. We will discuss crucial role of transitions combined of microwave absorption and elastic impurity scattering as well as their competition with pure impurity scattering. We further show [2] that dc electric field can effectively tune acoustic phonon resonances and induce a prominent resistance peak when electrons are accelerated to the speed of sound. Unrelated to microwave or phonon resonances, we also find that dc field can induce states with zero-differential resistance which appears to be analogous to the microwave-induced zero-resistance states. This work was supported by NSF Grant No. DMR-0548014.
[1] Zhang, Zudov, Pfeiffer, West, PRL 98, 106804 (2007)
[2] Zhang, Zudov, Pfeiffer, West, PRL 100, 036805 (2008)