Prof. Ross McKenzie: Bad metals, good superconductors, and quantum spin liquids
Source: Monday physics colloquium
Bad metals, good superconductors, and quantum spin liquids
Prof. Ross McKenzie, University of Queensland, Brisbane, Australia*
The discovery in 1986 of high-temperature superconductivity in layered copper oxide materials led to the development of revolutionary new concepts in theoretical solid state physics. These concepts include superconductivity from repulsive electronic interactions, quantum spin liquids, and bad metals. I will introduce these concepts and discuss how organic molecular charge transfer salts realise them . Small variations in hydrostatic pressure or in chemical composition reveal a subtle competition between Mott insulating, metallic, and superconducting states. Theoretical studies of the relevant Hubbard and Heisenberg models show how spin frustration is essential to stabilising different quantum spin liquid ground states and Resonating Valence Bond superconductors. Recent numerical results elucidate the bad metal associated with the transition out of the Mott insulating state.
 P.W. Anderson, Science 235, 1196 (1987).
 B.J. Powell and R.H. McKenzie, Rep. Prog. Phys. 74, 056501 (2011).
 J. Kokalj and R.H. McKenzie, Phys. Rev. Lett. 110, 206402 (2013).