Faculty of Science and Technology

Title: OVERCOMING RESISTANCE WITH QUANTUM PERSISTENCE

Abstract: Ironing a shirt, boiling water in a teapot, or reading under the light of incandescent bulb we know that electric current is pushed through a wire by voltage applied to its ends, and that by forcing their way through a metal electrons do generate heat. Yet, quantum mechanics gives electrons an opportunity to flow without any dissipation and thus in the absence of accelerating electric field. Being non-dissipative, such electric currents do not decay in time -- they are persistent. All one needs to create such current in a metallic loop is to pierce a magnetic flux through it - exotic effects like superonductivity can enhance these currents, but are not at all necessary. The profound reason for having the persistent current is the breaking of time-reversal symmetry by the flux. Thus persistent currents are quite ubiquitous, and actually share a common root with atomic diamagnetism. They are big and relatively easy to detect in superconducting closed circuits -- e.g., qubits. In non-superconducting rings, persistent currents are tiny, and were measured reliably only very recently. I will tell about two Yale experiments with persistent currents: the first involving a new type of qubit, "fluxonium", and the second involving non-superconducting rings, and about the theory behind these new exciting experiments.

Speaker: Leonid Glazman is a Professor of Physics and Applied Physics at Yale University since 2007, after being Director of the William I. Fine Institute of Theoretical Physics at the University of Minnesota. His field of research is condensed matter theory. He is a recognized expert in the physics of mesoscopic systems with major contributions to the theory of electron transport and correlations in systems of reduced dimensionality, such as quantum dots and quantum wires. During his career Prof. Glazman has authored more than 200 papers which received above 7000 citations in total. Among his accomplishments are the explanation of the conductance quantization in ballistic point contacts, successful prediction of the Kondo effect in conduction of quantum dots, and discovery of a new mechanism of electron energy relaxation mediated by magnetic impurites in metals. L. Glazman is a recepient of the Humboldt Research Award

for Senior U.S. Scientists and a Fellow of the American Physical Society.