Condensed Matter Physics Seminar
2 p.m., Thursday, Decemeber 7, 2006
Room 1201, Physics Building
A Cooper solid?: Electrodynamics of the 2D
Superconductor-Insulator Quantum Phase Transition
Peter Armitage
(Johns Hopkins University)
Abstract: The complex AC conductivity of thin amorphous InO films
was studied as a function of magnetic field through the nominal 2D
superconductor-insulator transition. We have resolved a significant finite
frequency superfluid stiffness well into the insulating regime, giving the first
direct evidence for superconducting correlations in this insulating state. As
these superconducting fluctuations are temperature independent at low
temperatures, this also represents the first observations of quantum
superconducting fluctuations around an insulating ground-state. A phase diagram
is established that includes the superconducting state, a transition to a 'Bose'
insulator and an eventual crossover to a 'Fermi' insulating state at high
fields. We speculate on the consequences of these observations, their impact on
our understanding of the insulating state, and its relevance as a prototype for
other insulating states of matter that derive from superconductors.
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Host: Greene
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