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• PUBLIC
  LECTURE

• Department of Physics
• Brown University
• Box 1843
• Barus Holley Building
• 182 Hope Street
• Providence, RI 02912
• physics @ physics.brown.edu

The BCS Theory of
Superconductivity

Brad Marston
Prof of Physics
Brown University

Prof. Marston's Brown University Research Profile


Lecture
"Gapless Spin Liquids: An Idea Whose Time Has Come"

Abstract
Since the discovery of the copper-oxide high-temperature superconductors two decades ago there has been intense interest in the possibility that some two-dimensional quantum antiferromagnets might be spin-liquids, that is, possessing ground states with no broken symmetries. It was widely anticipated that such ground states would exhibit a gap to spin excitations because gapless systems were expected to be susceptible to various forms of order, and also lack the protection provided by a Goldstone mechanism. It therefore comes as something of a surprise that the three best candidate materials for two-dimensional spin liquids appear to exhibit gapless (or nearly gapless) spin excitations. I review the history of the gapped and gapless spin liquids, and discuss recent calculations that lend theoretical support to the idea that gapless spin-liquids can exist in two and higher spatial dimensions.