Supercooled vortex liquid and quantitative theory of melting of the flux-line lattice in type-II superconductors

Abstract

A metastable homogeneous state exists down to zero temperature in systems of repelling objects. Zero "fluctuation temperature" liquid state therefore serves as a (pseudo) "fixed point" controlling the properties of vortex liquid below and even around melting point. There exists Madelung constant for the liquid in the limit of zero temperature which is higher than that of the solid by an amount approximately equal to the latent heat of melting. This picture is supported by an exactly solvable large N Ginzburg -Landau model in magnetic field. Based on this understanding we apply Borel -Pade resummation technique to develop a theory of the vortex liquid in type II superconductors. Applicability of the effective lowest Landau level model is discussed and corrections due to higher levels is calculated. Combined with previous quantitative description of the vortex solid the melting line is located. Magnetization, entropy and specific heat jumps along it are calculated. The magnetization of liquid is larger than that of solid by 1.8% irrespective of the melting temperature. We compare the result with experiments on high T c cuprates Y Ba 2 Cu 3 O 7 , DyBCO, low T c material (K, Ba)BiO 3 and with Monte Carlo simulations.

Superconducting fluctuations and the Nernst effect in high-Tcsuperconductors

“…The Gi number describing the strength of fluctuations varies from 1.2 × 10 −4 (p = 0.10) to 5 × 10 −5 (p = 0.20). This is consistent with the previous values deduced from the thermodynamic experiments (magnetization and specific heat) [27,32] and the melting line [33]. The Gi number and anisotropy parameter as a function of p are shown in figure 4.…”

Vortex-lattice melting and paramagnetic depairing in the nematic superconductor FeSe

“…Further, we note that the midpoint of our broad melting discontinuity lies around a T ≈ −11, i.e., below the Li-Rosenstein value [94][95][96][97][98] (a T = −9.5) calculated for an ideal vortex lattice. We ascribe this difference to the weak flux pinning observed in our thermal-expansion measurements.…”

“…In Fig. 4, we compare our scaled heat-capacity data to the calculations of Li and Rosenstein [94][95][96][97][98] (thick solid line) who successfully derived an analytical expression of the 3D-LLL scaling function for −25 < a T < 8, which includes the expected contributions from vortex melting. This expression was found to describe the broadening of the calorimetric transitions and the melting discontinuity in RbEuFe 4 As 4 [31] extremely well.…”

Melting of vortex lattice in the magnetic superconductor RbEuFe4As4

“…The transition somewhat sharpens when resistivity drops below ∼ 60% of the normal level forming The black dashed line is the theoretical LLL scaling function following from calculations in Refs. [50,52]. 4 The dominating contribution to the specific-heat scaling function is given by the last term in Eq.…”

“…(57) of Ref. [50], which is proportional to the second derivative of the free-energy scaling function. The shape of this function plotted in Fig.…”