Field-dependent resistive transitions in YBa ₂ Cu ₃ O _{7− δ} thin films: Influence of the pseudogap on vortex dynamics

Abstract

The nature of resistive transition of high-quality crystalline thin films of YBa 2 Cu 3 O 7−δ has been studied under magnetic fields (H) applied along the c direction over a wide range of doped holes, p, in the CuO 2 planes. The field-and temperature-dependent in-plane resistivity, ρ ab (T, H), has been analyzed within the thermally assisted flux-flow (TAFF) formalism. The flux activation energy, U(T, H), has been extracted from this analysis. The low-T part of the ρ ab (T, H) data can be described by an activation energy having the functional form of U(T, H) = (1 −t) m (H 0 /H) −β , where t = T /T c (reduced temperature), and H 0 is a field scale that primarily determines the magnitude of U(T, H). The temperature exponent, m, shows a systematic variation with p, whereas the field exponent, β , is insensitive to the p values and is close to unity. The H 0 , on the other hand, changes rapidly as p is varied. U(T, H) is linked to the pinning potential and consequently on the superconducting condensation energy. Since the normal state pseudogap directly affects superconducting condensation energy, a clear correspondence between H 0 and the PG energy scale, ε g , is found. Possible implications of these results are discussed.

Magnetotransport properties and pseudogap phase diagram of superconducting EuBa2Cu3Oy thin films: the influence of Eu substitution

“…The values of exacted activation energy U * for S91 in different fields are also shown in figure 5 for comparison. As seen, the zero-temperature U * is reasonably much larger than that determined from the simple Arrhenius plot, U, and also shows a power-law dependence U * ∝ H −α with α=0.93±0.02, which is near unity as previously reported [37]. The different α values in the power-law dependences of U and U * are possibly due to the different temperature regions extracted from the ρ(T) curve.…”

“…Surprisingly, little attention has been given to this interesting observation. Recently, Naqib and Islam [37] showed a greatly significant effect of doped hole number p on the activation energy U in YBCO films via changing the oxygen deficiency in the Cu−O chains, as conducted by this study. They demonstrated that the dimensionless activation energy can be expressed as U(T, H)=(1 − t) m (H 0 /H) β , where t is the reduced temperature and H 0 is a characteristic field scale.…”

“…Furthermore, since the activation energy is determined at different reduced temperatures, it is necessary to take account of the temperature and field dependences. A modified method to calculate the activation energy from the resistance transition has been proposed [36,37]. Following the procedures given in [36,37], we extract the temperature dependence of U with a choice of U(t)=U * (H)(1 − t) m , where the reduced temperature t=T/T c (H), U * (H) corresponds to the activation energy at 0 K, and m=2 as given in this modified method.…”

“…A modified method to calculate the activation energy from the resistance transition has been proposed [36,37]. Following the procedures given in [36,37], we extract the temperature dependence of U with a choice of U(t)=U * (H)(1 − t) m , where the reduced temperature t=T/T c (H), U * (H) corresponds to the activation energy at 0 K, and m=2 as given in this modified method. Here T c (H) is the mean-field transition temperature which can be estimated from the resistive transition curves in fields.…”

Possible quantum critical behavior revealed by the critical current density of hole doped high-Tc cuprates in comparison to heavy fermion superconductors

“…Details regarding the magnetic field dependent resistivity ( ρ ab ( H , T )) measurements and analysis of the flux dynamics can be found in ref. 36 . All the measurements presented for Y 1− x Ca x Ba 2 Cu 3 O 7− δ in this study were done for the H II c configuration, where the supercurrent circulated in the CuO 2 plane.…”