Entropy of Vortex Cores Near the Superconductor-Insulator Transition in an Underdoped Cuprate

Abstract

We present a study of Nernst effect in underdoped La(2-x)Sr(x)CuO4 in magnetic fields as high as 28 T. At high fields, a sizable Nernst signal was found to persist in the presence of a field-induced nonmetallic resistivity. By simultaneously measuring resistivity and the Nernst coefficient, we extract the entropy of vortex cores in the vicinity of this field-induced superconductor-insulator transition. Moreover, the temperature dependence of the thermoelectric Hall angle provides strong constraints on the possible origins of the finite Nernst signal above T(c), as recently discovered by Xu et al. [Nature (London) 406, 486 (2000)].

Nernst effect in high-Tcsuperconductors

“…Indeed, curves taken at 20 K are comparable in magnitude with many of those below T c . Similar results have been obtained by Capan et al [24]. Hence from the perspective of the Nernst effect, the boundary between the superconducting state and the normal state in UD cuprates is truly blurred.…”

Bose–Einstein condensation of strongly correlated electrons and phonons in cuprate superconductors

“…In particular, the bipolaron theory accounts for the anomalously large Nernst signal, the thermopower and the insulating-like in-plane low temperature resistance [47,48] as observed [51,64,65,66].…”

Anomalous dissipation in the mixed state of underdoped cuprates close to the superconductor-insulator boundary

“…Remarkably, the temperature scale up to which such an anomalous Nernst signal extends is about 130K, regardless of the particular system studied. Moreover, the Nernst signal is found to persist at magnetic fields as high as 30T both in overdoped [3] and in underdoped [4] compounds.The debate on the origin of this residual Nernst signal in the normal state of underdoped cuprates is still open and has stimulated a number of theoretical works during the past months. Fluctuations of the superconducting order parameter above T c are considered to be the most plausible explanation for such a signal.…”

“…Remarkably, the temperature scale up to which such an anomalous Nernst signal extends is about 130K, regardless of the particular system studied. Moreover, the Nernst signal is found to persist at magnetic fields as high as 30T both in overdoped [3] and in underdoped [4] compounds.…”

“…Jf, 74.25.Fy, 74.40.+k, 74.60.Ge Recently, the peculiar behavior of Nernst effect in copper oxide superconductors has become a subject of growing attention [1,2,3,4,5,6,7,8,9]. In conventional superconductors, Nernst effect, namely the transverse component of the thermopower in a magnetic field, is known to be associated with vortex movement [10].…”