Spontaneously translational symmetry breaking in the excited states of holographic superconductor

TL;DR

This paper explores spontaneous translational symmetry breaking in excited states of a holographic superconductor model, revealing new solutions where symmetry is broken without external periodic sources, and analyzing their thermodynamic stability.

Contribution

It introduces solutions with broken translational symmetry in excited states of the holographic superconductor, extending previous models and analyzing their temperature dependence and free energy.

Findings

Broken translational symmetry occurs spontaneously in excited states.

Non-translational invariant solutions have lower free energy.

Condensates vanish at low temperatures, related to lattice length.

Abstract

We revisit HHH model in [Phys. Rev. Lett. {\bf 101}, 031601 (2008)] and extend the ansatz of matter fields to being of depending on a spatial dimension except the holographic direction. Despite homogeneous solutions of ground and excited states, especially for the excited states, there also exists solutions where the translational invariance is broken. It is worth mentioning that no periodic sources are assigned to the matter fields, so the translational symmetry is broken spontaneously. We investigate how the new solutions and the condensates of excited states develop with the change of temperature. Moreover, since this kind of condensate will decrease at certain temperature and eventually vanish at sufficiently low temperature, we also study the relation between this interval and length of lattice. Besides, we compare the free energies of non-translational invariant solutions and those of translational invariance in the HHH model, and find that the free energies of the former situations are lower.