Excited states of holographic superconductors with backreaction

In this paper we investigate the model of the anti-de Sitter gravity coupled to a Maxwell field and a free, complex scalar field, and construct a fully back-reacted holographic model of superconductor with excited states. With the fixed charge q, there exist a series of excited states of holographic superconductor with the corresponding critical chemical potentials. The condensates as functions of the temperature for the two operators $${\mathcal {O}}_1$$ O 1 and $${\mathcal {O}}_2$$ O 2 of excited states are also studied. For the optical conductivity in the excited states, we find that there exist the additional peaks in the imaginary and real parts of the conductivity. Moreover, the number of peaks corresponding to n-th excited state is equal to n.

Holographic subregion complexity in unbalanced holographic superconductors

By using the subregion CV conjecture, we numerically investigate the behavior of the holographic subregion complexity (HSC) and compare it with the holographic entanglement entropy (HEE) in the unbalanced holographic superconductors, which indicates that both the HEE and HSC can be used as good probes to the phase transition in unbalanced holographic superconductors. We observe that the HEE and HSC exhibit a similar linear growth behavior with the change of width for a strip geometry. However, for different fixed widths, the HSC exhibits different behaviors with the change of the temperature, while the behavior of HEE remains consistent. In particular, we find that there are certain conditions that make it difficult to observe the phase transition of this system through the HSC approach. Furthermore, we also note that the unbalance parameter has different effects on the HSC, while the HEE always increases as the unbalance parameter increases.

Holographic superconductors in 4D Einstein-Gauss-Bonnet gravity

We investigate the neutral AdS black-hole solution in the consistent D → 4 Einstein-Gauss-Bonnet gravity proposed in [K. Aoki, M.A. Gorji, and S. Mukohyama, Phys. Lett. B810 (2020) 135843] and construct the gravity duals of (2 + 1)-dimensional superconductors with Gauss-Bonnet corrections in the probe limit. We find that the curvature correction has a more subtle effect on the scalar condensates in the s-wave superconductor in (2 + 1)-dimensions, which is different from the finding in the higher-dimensional superconductors that the higher curvature correction makes the scalar hair more difficult to be developed in the full parameter space. However, in the p-wave case, we observe that the higher curvature correction always makes it harder for the vector condensates to form in various dimensions. Moreover, we note that the higher curvature correction results in the larger deviation from the expected relation in the gap frequency ωg/Tc ≈ 8 in both (2 + 1)-dimensional s-wave and p-wave models.