Do Superconductors Have Zero Resistance in a Magnetic Field?

Abstract

We show that dc voltage versus current measurements of a YBa(2)Cu(3)O(7-delta) film in a magnetic field can be collapsed onto scaling functions proposed by Fisher et al. [Phys. Rev. B 43, 130 (1991)] as is widely reported in the literature. We find, however, that good data collapse is achieved for a wide range of critical exponents and temperatures. These results strongly suggest that agreement with scaling alone does not prove the existence of a phase transition. We propose a criterion to determine if the data collapse is valid, and thus if a phase transition occurs. To our knowledge, none of the data reported in the literature meet our criterion.

Phase behavior of type-II superconductors with quenched point pinning disorder: A phenomenological proposal

“…Gauge glass models for the VG transition do not show a finite T transition in three dimensions, once effects of screening are included [71]. Also, recent work questions earlier reports supporting a scaling description of the experimental data on disordered cuprates [72,73]. Theoretically, the evidence appears to favour a low-temperature glassy phase without long-ranged phase correlations, at least in the weak disorder limit [11].…”

Flux pinning and vortex transitions in doped BaFe2As2 single crystals

“…Although Strachan et al 15 suggested that agreement with scaling alone does not prove the existence of a phase transition, but experimental evidence for the vortex-glass phase has been obtained for various high-T c superconductors such as Y-123, [10][11][12] Tl-2212, 13,14 MgB 2 , 16 and Ba 0.55 K 0.45 Fe 2 As 2 (Ref. 17) through the scaling exponent, as predicted by vortex-glass and modified vortex-glass theory.…”

Zero-magnetic-field dynamic scaling inBi2Sr2CaCu2O8Sefrioui1, Arias2, León3 et al. 2004Phys. Rev. B10020View full textAdd to dashboardCite

“…In the following we use scaling arguments to show that this is actually a BKTlike transition and to obtain the critical exponent z and the transition temperature. The transition temperature is obtained from the derivative plot as suggested by Strachan et al 19,20 The proposed criterion for I-V data is that log V vs log I isotherms above and below T BKT must have opposite concavities at the same applied currents. Figure 1(b) shows the current dependence of the derivative of the log V vs log I isotherms of Fig.…”

“…It is worth noting that the resistance data drops abruptly below 87 K suggesting a true superconducting state in our pure 2D system below 86 K. It is interesting to remark that the same set of parameters z , b, and T BKT consistently accounted for the resistance measurements and for the scaling, which is not necessarily the case if the opposite concavity criterion by Strachan et al is not observed. 19,20 Due to the large scaling flexibility equally satisfactory scaling plots can be constructed for different sets of b , z, and T BKT . In fact, if we tentatively fix the value of z = 2 for conserving the concept of universality of the BKT, it is actually possible to scale the data of Fig.…”

“…A zero field BKT transition has been reported for the highly anisotropic BSCCO and TBCCO superconductors 11-14 assuming but not testing the value z =2. In fact quite high values of z ϳ 6 have been reported 5 19,20 is used to arrive at the correct exponent and critical temperature from scaling arguments. Fresh Bi 2 Sr 2 CaCu 2 O 8 films show a BKT-like transition with z = 0.8, smaller than expected for the BKT transition but similar to that observed in frustrated Josephson junction arrays (JJA).…”