APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016;
Baltimore, Maryland
Session C13: DMP Prize Session
2:30 PM–5:30 PM,
Monday, March 14, 2016
Room: 309
Sponsoring
Unit:
DMP
Chair: Michael E. Flatté, University of Iowa
Abstract ID: BAPS.2016.MAR.C13.2
Abstract: C13.00002 : Frank Isakson Prize for Optical Effects in Solids: Optical spectroscopy and mechanisms of superconductivity.
3:06 PM–3:42 PM
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Abstract
Author:
Dirk van der Marel
(University of Geneva)
By its very nature the phenomenon of superconductivity is intimately
connected to the electrodynamics properties of a material, both in the
normal and in the superconducting state. Optical spectroscopy and electrical
transport -corresponding to the zero-frequency limit of the optical
response- provide for this reason sensitive tools probing the collective
response of a superconducting material. Optical spectroscopy can provide the
real and imaginary parts of the optical conductivity of an electron liquid
for all frequencies from radiowaves through infrared and visible up to the
ultraviolet and even X-ray frequencies. Theory of the optical response is
particularly well developed, leading among others to a number of sumrules,
providing powerful tools for confronting experiment and theoretical models
of superconducting pairing. In this talk examples of sumrules will be
discussed relating to the kinetic energy and the Coulomb energy of the
paired electrons, and experimental data of addressing these two energies
will be presented.
The basic understanding of pair formation in the conventional (i.e. BCS)
model of superconductivity is, that electrons form pairs as a result of an
attractive interaction. On general grounds one than expects the interaction
energy to become reduced when the electrons form pairs, while at the same
their kinetic energy increases. Superconductivity is a stable state of
matter provided that all contributions together result in a lowering of the
total (interaction, kinetic plus other terms if relevant) lowering of
energy. In this talk I will demonstrate that these two effects can be
observed in the cuprate superconductors, that behave according to
aforementioned trends for strongly overdoped cuprates, but that the observed
effects have the opposite sign for underdoped and optimally doped cuprates.
These observations compare favorably with published numerical calculations
based on models of strong electron-electron correlation, not involving the
vibrations of the lattice, and where the electron-electron interaction is
purely repulsive.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2016.MAR.C13.2