University of Minnesota
School of Physics & Astronomy

Condensed Matter Sack Lunch Seminar

Tuesday, February 3rd 2009
12:20 pm:
Condensed Matter Seminar in 435 Physics
Speaker: Ania Bleszynski-Jayich, Yale University
Subject: Measurements of persistent currents in normal metal rings using a micromechanical magnetometer
Ania Bleszynski-Jayich is a candidate for the Cond. Matter Experimentalist Asst. Prof. position.

A striking manifestation of quantum mechanics is the existence of a dissipationless current in a non-superconducting metal ring. The persistent current is analogous to electrons orbiting the nucleus in an atom, a more familiar quantum effect. The persistent current is a signature of electronic phase coherence around the ring and offers insight into many issues in mesoscopic physics such as coherence and electron interactions in metals. The prediction that an atom-like persistent current could be observed in a micron size metal ring generated considerable interest. However, the small magnitude of the current and the necessity of measuring it through its associated magnetic moment make persistent current experiments challenging. Few measurements have been reported and inconsistent results have left an unclear picture of the properties of persistent currents. In a novel approach to studying persistent currents we have developed a cantilever based torsional magnetometer capable of detecting a magnetic moment of 1 μB/Hz1/2 (and a force of 1.6 aN/Hz1/2) at a temperature of 300 mK. The rings are integrated directly onto the end of the cantilever. I present measurements of persistent currents in arrays of rings and single rings as a function of temperature, ring size, and magnetic field over a much broader range than previously possible. We compare our results to theory and previous experiments.

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