Thermal activation energy for Cuprates from a Multilayer Boson-Fermion Model*

In the mixed state, Type II superconductors, such as cuprates and pniptides, which present a cuasi-2D layered structure, permit a vortex flux flow penetration in the presence of an external magnetic field B, arranged in the form of an Abrikosov net.  However, between the lower critical field H_c1 and the upper critical field  H_c2 and near T_c , thermal fluctuations directly affect the vortex motion (TAFF) [1], so a thermal activation energy  U(T,B) must be overcome to allow flux motion and changing the  resistivity.

Here we report the thermal activation energy using the expression U(T,B)=Φ²₀H_c(T)/(2√2πλ(T)μ₀H), which is obtained combining the phenomenological relation from Yeshurun et al. with the G-L relation  H_c(T)=Φ₀/(2√2πλ(T)ξ(T)) [2], where we use the expressions for the coherence  ξ(T) and penetration λ(T)  lengths previously obtained applying the Multilayer Boson-Fermion model of superconductivity [3] for underdoped cuprates.

The comparison of our results with the experimental data show a better agreement than the ones reported in the literature using other models.

1. Hettinger, et al., PRL 62, 2044 (1989).

2. Tinkham, PRL 61, 1658 (1988).

3.  P. Salas et al. Physica C 524, 37 (2016).