domingo, 25 de julio de 2010

Physics of High-Temperature Cuprate Superconductors


The cuprate superconductors are doped Mott insulators whose phase diagram exhibits numerous departures from Fermi liquid theory, most notably the pseudogap and strange metal (resistivity scaling linearly with temperature) regimes of the normal state. Typical approaches to this problem include 1) phenomenology based on some preferred ordered state, 2) numerical simulations, and 3) inspired guesses as to the low-energy degrees of freedom. Our work aims to establish a general principle from which the inherent strong-coupling physics of a doped Mott insulator arises. Ultimately the route to solving any strongly coupled problem is to isolate the propagating degrees of freedom. Typically the propagating modes cannot be read off by inspecting a Hamiltonian but rather are dynamically generated through a collective organization of the elemental fields. In identifying the principle that leads to such organization, it helps to know what to throw out. A ubiquitous phenomenon in strongly correlated systems such as a doped Mott insulator, not seen in weakly interacting systems, is spectral weight transfer over wide energy scales. The general class of phenomena arising from such transfer of spectral weight we termed Mottness. Determining what are the strongly correlated entities that get rid of spectral weight transfer would then re-instate a rigid band picture, rendering the problem then weakly coupled. We have succeeded in doing precisely this by integrating out exactly the high-energy degrees of freedom in a doped Mott insulator described by the Hubbard model. New propagating degrees of freedom, bound states of holes and charge 2e bosons, emerge which are capable of explaining the pseudogap and the transition to the strange metal regimes. Much of our current effort is on elucidating how these new degrees of freedom pair up to form the superconducting state.

Nombre: Franklin J. Quintero C.
Asignatura: CRF
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