Density functional theory for freezing transition of vortex-line liquid with periodic layer pinning

TL;DR

This paper uses density functional theory to analyze the freezing transition of vortex lines in layered superconductors, revealing a two-step transition involving smectic and lattice phases influenced by layer pinning.

Contribution

It demonstrates that strong layer pinning stabilizes a smectic phase with period m=2 and maps out phase diagrams, providing new insights into vortex matter in layered superconductors.

Findings

A smectic phase with period m=2 can be stabilized by layer pinning.

Vortex liquid freezing involves a second-order smectic transition and a first-order lattice transition.

Direct first-order transitions occur for m>2 regardless of pinning strength.

Abstract

By the density functional theory for crystallization, it is shown that for vortex lines in an underlying layered structure a smectic phase with period m=2 can be stabilized by strong layer pinning. The freezing of vortex liquid is then two-step, a second-order liquid-smectic transition and a first-order smectic-lattice transition. DFT also indicates that a direct, first-order liquid-lattice transition preempts the smectic order with m>2 irrespectively of the pinning strength. Possible H-T phase diagrams are mapped out. Implications of the DFT results to the interlayer Josephson vortex system in high-Tc cuprates are given.