The quantum critical point of cuprate superconductors
Institut Quantique, Département de physique, Université de Sherbrooke
Canadian Institute for Advanced Research, Toronto, Canada
Abstract: By suppressing superconductivity with a large magnetic field, we have investigated the metallic ground state of several cuprate superconductors in the T = 0 limit (YBCO, Bi2212, LSCO, Nd-LSCO, Eu-LSCO, Bi2201), via measurements of resistivity, Hall and Seebeck coefficients, thermal conductivity and specific heat. We observe a sharp transition at a critical doping p*, into the enigmatic pseudogap phase. The key signature is a drop in carrier density n from n = 1 + p above p* to n = p below p* [1,2], signaling a major transformation of the Fermi surface. At p*, we observe the classic signatures of quantum criticality: the electrical resistivity is linear in T at low T [2,3,4] and the electronic specific heat Cel shows a sharp peak at p*, where it varies in temperature as Cel ~ – T logT . Understanding the mechanisms responsible for these various signatures will help elucidate the nature of the enigmatic pseudogap phase of cuprates.
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