title: Zero-resistance states induced by electromagnetic-wave excitation in GaAs/AlGaAs heterostructures.
abstract: The observation of vanishing electrical resistance in condensed matter has led to the discovery of new phenomena such as, for example, superconductivity, where a zero-resistance state can be detected in a metal below a transition temperature T(c) (ref. 1). More recently, quantum Hall effects were discovered from investigations of zero-resistance states at low temperatures and high magnetic fields in two-dimensional electron systems (2DESs). In quantum Hall systems and superconductors, zero-resistance states often coincide with the appearance of a gap in the energy spectrum. Here we report the observation of zero-resistance states and energy gaps in a surprising setting: ultrahigh-mobility GaAs/AlGaAs heterostructures that contain a 2DES exhibit vanishing diagonal resistance without Hall resistance quantization at low temperatures and low magnetic fields when the specimen is subjected to electromagnetic wave excitation. Zero-resistance-states occur about magnetic fields B = 4/5 Bf and B = 4/9 Bf, where Bf = 2pifm*/e,m* is the electron mass, e is the electron charge, and f is the electromagnetic-wave frequency. Activated transport measurements on the resistance minima also indicate an energy gap at the Fermi level. The results suggest an unexpected radiation-induced, electronic-state-transition in the GaAs/AlGaAs 2DES.
authors.affiliation: Gordon McKay Laboratory of Applied Science, Harvard University, 9 Oxford Street, Cambridge, Massachusetts 02138, USA. mani@deas.harvard.edu
authors.forename: Ramesh G
authors.initials: RG
authors.lastname: Mani
authors.forename: Jürgen H
authors.initials: JH
authors.lastname: Smet
authors.forename: Klaus
authors.initials: K
authors.lastname: von Klitzing
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Narayanamurti
authors.forename: William B
authors.initials: WB
authors.lastname: Johnson
authors.forename: Vladimir
authors.initials: V
authors.lastname: Umansky