Absence of hexagonal-to-square lattice transition in LiFeAs vortex matter

The hexagonal versus the square lattice

Schmutz Schaller’s conjecture regarding the lengths of the hexagonal versus the lengths of the square lattice is shown to be true. The proof makes use of results from (computational) prime number theory. Using an identity due to Selberg, it is shown that, in principle, the conjecture can be resolved without using computational prime number theory. By our approach, however, this would require a ...

The Phase Transition to a Square Vortex Lattice in Type-II Superconductors with Fourfold Anisotropy

We investigate the stability of the square vortex lattice which has been recently observed in experiments on the borocarbide family of superconductors. Taking into account the tetragonal symmetry of these systems, we add fourfold symmetric fourth-derivative terms to the Ginzburg-Landau(GL) free energy. At Hc2 these terms may be treated perturbatively to lowest order to locate the transition fro...

Vortex lattice transition in D-wave superconductors

Making use of the extended Ginzburg Landau theory, which includes the fourth order derivative term, we study the vortex state in a magnetic field parallel to the c axis. The vortex core structure is distorted due to this higher order term, which reveals the fourfold symmetry. Further, this distortion gives rise to the core interaction energy, which favors a square lattice tilted by 45 from the ...

Spin transport in the square lattice vortex state of rotational

Structural phase transitions of vortex matter in an optical lattice.

We consider the vortex structure of a rapidly rotating trapped atomic Bose-Einstein condensate in the presence of a corotating periodic optical lattice potential. We observe a rich variety of structural phases which reflect the interplay of the vortex-vortex and vortex-lattice interactions. The lattice structure is very sensitive to the ratio of vortices to pinning sites and we observe structur...