Magnetic penetration depth

In contrast to the conventional s-wave superconductor picture above, Gasparov et al. (2006) report unusual temperature dependence of the magnetic penetration depth A.(T) and upper critical field Hc2(T) and propose that ZrBi2 has an unconventional two-gap superconductivity. 

Figure 2.34 illustrates these serious experimental problems. In the upper part (a) the magnetic penetration depth of k-(ET)2Cu(NCS)2 measured by ac susceptibility [220] and in the lower part (b) the same quantity obtained by dc magnetization [227] is shown. The clear discrepancy of the behavior of A(T) at low temperatures is obvious. In the ac-susceptibility experiment consistent with [221, 222, 223] a variation is found. This non-exponential non-BCS dependence can be explained with energy-gap nodes of several different topologies [222]. On the other hand, the data of [227] could very well be described by conventional weak-coupUng theory in the clean limit as shown... 

Fig. 2.34. Temperature dependence of the in-plane magnetic penetration depth extracted from (a) ac-susceptibility and (b) dc-magnetization measurements. The inset in (b) shows the low-T data in enlarged scale together with model curves for BCS (solid line) and for two triplet states, ti and t4 (broken curves). From [220] and [227]...

Fig. 4. The temperature dependence of the magnetic penetration depth of the paired holon superconductor (solid line) compared with the experimental data of YBa2Cu307 8. The data is from Cooper et al. (Ref. 14).

D.R. Harshman, R. N. Kleiman, M. Inui, G.P. Espinosa, D.B. Mitzi, A. Kapitulnik, T. Pfiz, 2.98 D. L. Williams Magnetic penetration depth and flux dynamics in single crystal Bi2Sr2CaCu20s-8, Phys. 

S Kohjiro, A Shoji, S Kiryu. Magnetic penetration depths and normal-state resistivities of epitaxial and polycrystaUine NbC -Ni-, films. Jpn J Appl Phys 3LL239, 1992. 

S Kubo, M Asahi, M Hikita, M Igarashi. Magnetic penetration depths in superconducting NbN films prepared by reactive dc magnetron sputtering. Appl Phys Lett 44 258, 1984. 

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