Density driven symmetry breaking in holographic superconductors

We study the density driven symmetry breaking in holographic superconductors by considering the positive mass squared case. We show that even for the positive m(2), a scalar condensation still forms, provided the chemical potential is high enough. As m(2) increases, the phase space folds due to the nonlinearity of the equations of motion, and two nearby points in the phase space can represent symmetry breaking and preserving configurations, respectively. The phase space defined by the set of initial conditions of field variables at the horizon undergoes a nonlinear radial evolution to result in the phase space folding, a characteristic phenomenon in a nonlinear system. We then calculate the specific heat, which characterizes superconductors and has been measured in experiments. We observe a discontinuity in the specific heat at the transition point and compare our results with experimentally observed numbers. The electrical conductivity for various m(2) is also calculated.We want to thank P. Basu, S. Hartnoll, and A. Yarom for useful comments on the first version of the paper. This work was supported in part by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) through the Center for Quantum Spacetime (CQUeST) of Sogang University with grant number 2005-0049409. The work of S. J. Sin was also supported in part by KOSEF Grant R01-2007-000-102140. Y. Kim acknowledges the Max Planck Society (MPG), the Korea Ministry of Education, Science, Technology (MEST), Gyeongsangbuk-Do and Pohang City for the support of the Independent Junior Research Group at the Asia Pacific Center for Theoretical Physics (APCTP)