Boston Chapter of the IEEE Photonics Society

Abstract:  Quantized Hall states are peculiar states that can occur in two-dimensional electron systems at low temperatures in a strong magnetic field.  At the edge of such a state, there is necessarily a conducting channel, in which electrons can flow in only one direction.  Interference between electrons in different channels can occur in geometries with constrictions, where two edges come close enough together that electrons can tunnel between them.  Fabry-Pérot and Mach-Zehnder-type interference has been observed, as has a two-particle interference between electrons from independent sources, analogous to the Hanbury Brown-Twiss effect for photons. To understand the variety of observed interference patterns, however, it is necessary to take into account the Coulomb interaction between electrons in the system, as well as the Aharanov-Bohm phase-shift for electron trajectories in a magnetic field.

Biography:  Bertrand Halperin's research interests concern many aspects of the theory of condensed matter systems and statistical physics. Over the years, his work has included contributions to the theories of static and dynamic critical phenomena, including melting and other phase transitions in two-dimensional systems; quantum antiferromagnets in one and two dimensions, one-dimensional metals;  superconductivity; low-temperature properties of glasses; and transport in inhomogeneous media.  A major portion of Halperin's work has concerned properties of two-dimensional electron systems at low temperatures in strong magnetic fields, or "quantum Hall systems".  Much of his current research involves the theory of electron states and transport in small particles of a metal or semiconductor.  Much of this work has been motivated by experiments carried out in various laboratories at Harvard.