Abstract
The Nernst effect was measured in the electron-doped cuprate superconductor (PCCO) at four concentrations, from underdoped to overdoped , for a wide range of temperatures above the critical temperature . A magnetic field up to 15 T was used to reliably access the normal-state quasiparticle contribution to the Nernst signal , which is subtracted from the total signal , to obtain the superconducting contribution . As a function of , peaks at a field whose temperature dependence obeys ), as it does in a conventional superconductor such as . The doping dependence of the characteristic field scale , shown to be closely related to the upper critical field , tracks the domelike dependence of , showing that superconductivity is weakened below the quantum critical point where the Fermi surface is reconstructed, presumably by the onset of antiferromagnetic order. Our data at all dopings are quantitatively consistent with the theory of Gaussian superconducting fluctuations, eliminating the need to invoke unusual vortexlike excitations above , and ruling out phase fluctuations as the mechanism for the fall of with underdoping. We compare the properties of PCCO with those of hole-doped cuprates and conclude that the domes of and versus doping in the latter materials are also controlled predominantly by phase competition rather than phase fluctuations.
12 More- Received 23 May 2014
- Revised 1 July 2014
DOI:https://doi.org/10.1103/PhysRevB.90.024519
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