August 29 , 2007
3 pm in Howey Physics Lecture Room 5

 

Ramesh Mani, Professor

Department of Physics & Astronomy
Georgia State University

 

" RADIATION-INDUCED ZERO-RESISTANCE STATES IN LOW DISORDER 2-DIMENSIONAL ELECTRON SYSTEMS "

Quantum Hall effect and superconductivity have shown that observation of vanishing resistance in unusual settings can be a harbinger of new physics. We present our experimental discovery of the novel zero-resistance states that appear in the ultra-high mobility 2-D electron systems irradiated by low energy photons. At low temperatures, the GaAs/AlGaAs 2-D electron system exhibits vanishing diagonal resistance, without Hall resistance quantization, when the sample is excited by radiation in the microwave and terahertz parts of the electromagnetic spectrum. Zero-resistance-states are observed at B = [4/(4j+1)] Bf, j=1, 2, 3 …, where Bf = 2p f m*/e, m* is the electron mass,  e is the electron charge and f is the radiation frequency. We also discuss the theoretical understanding of this fascinating effect.