Condensed Matter Physics Seminar
2 p.m., Thursday, October 18, 2001
Room 1201, Physics Building
Schizophrenic Electrons in Flatland: Physics of Which Layer?
Sankar Das Sarma
(Department of Physics, University of Maryland)
Abstract: I will talk about a most peculiar phenomenon where
electrons in a bilayer system (i.e. electrons confined in two parallel thin
two-dimensional layers separated by some distance) lose their layer identity and
do not 'know' which layer they belong to EVEN IN THE STRICT ABSENCE OF ANY
INTER-LAYER TUNNELING. The electrons go 'schizophrenic' as the charge density in
individual layers is no longer a good quantum number, and there is a spontaneous
breaking of the U(1) symmetry in each layer leading to all kinds of good things
such as Goldstone mode, supefluidity, X-Y ferromagnetism of a very special kind,
Bose condensation of inter-layer excitons, Kosterlitz-Thouless transition, and
possibly even a strange new type of Josephson effect. To top it off I will
discuss recent experiments which have compellingly established the real
existence in nature of this strange 'spontaneous interlayer coherence'
phenomenon in bilayer quantum Hall systems. A partial elementary discussion of
some of the things (but, not all!) I will discuss in my talk can be found in the
Search and Discovery section of the May 2001 issue of Physics Today (Barbara
Goss Levi, Physics Today Vol.54, #5, p.14 (2001)).
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