Phase Fluctuations and the Pseudogap inYBa2Cu3Ox

Abstract

The thermodynamics of the superconducting transition is studied as a function of doping using high-resolution expansivity data of YBa(2)Cu(3)O (x) single crystals and Monte Carlo simulations of the anisotropic 3D- XY model. We directly show that T(c) of underdoped YBa(2)Cu(3)O (x) is strongly suppressed from its mean-field value (T(MF)(c)) by phase fluctuations of the superconducting order parameter. For overdoped YBa(2)Cu(3)O (x) fluctuation effects are greatly reduced and T(c) approximately T(MF)(c). We find that T(MF)(c) exhibits a similar doping dependence as the pseudogap energy, naturally suggesting that the pseudogap arises from phase-incoherent Cooper pairing.

Critical fluctuations and pseudogap observed in the microwave conductivity ofBi2Sr2CaCuPeligrad1, Mehring2, Dulčić3 2004Phys. Rev. B122100View full textAdd to dashboardCite

“…Later on, the penetration depth measurements in Y Ba 2 Cu 3 O 7−δ revealed critical behavior as wide as ±10K from T c , 7 belonging to the universality class 3D XY. More recent measurements of thermal expansivity 8,9 and two-coil inductive measurements 10 have confirmed this wide range of critical fluctuations, while dc fluctuatuation conductivity measurements still claimed very narrow critical regions 11,12,13,14,15,16 . A major problem in the analysis of a dc fluctuation conductivity is to account for the short wavelength cutoff, 5,6,11,15 and energy cutoff 17,18 at higher temperatures.…”

“…12 reveals the existence of two critical regimes with the static critical exponents ν = 2/3 well above T c , and a crossover to ν = 1 when T c is approached. The former critical regime corresponds to the 3D XY universality class, and has been reported before 8,9,10 . However, the well defined crossover to the critical regime with ν = 1 is novel and surprising.…”

Phase separation models for cuprate stripe arrays

“…Further evidence for this can be found by comparing the superconducting fluctuations [107][108][109][110]87 , Fig. 15.…”

“…15. [ 107] and (diamonds) [ 87], LSCO (triangles) [ 108], and YBCO (closed squares) [ 109] and (open squares) [ 110].…”

Thermal fluctuations and vortex melting in theNb3Snsuperconductor from high resolution specific heat measurements

“…We observe in the 0.25 T data that the anomaly represents 3% of the specific-heat jump and it appears over a temperature range ϳ10 −2 K. For comparison, G for the HTSC YBa 2 Cu 3 O 7 ͑YBCO͒ is of the order of 1 K, while fluctuation contributions have been observed up to 30 K above T c . 4,5 Furthermore, G increases in a field due to a reduction of the effective dimensionality arising from the confinement of the excitations to a few low Landau orbits. 24 This lead to the observation of fluctuations in some classical superconductors, especially in Nb, in rather high fields close to H c2 ͑0͒ which have been interpreted in terms of "lowest Landau level" ͑LLL͒ fluctuations.…”