Holographic insulator/superconductor transitions in the three   dimensional AdS soliton
  We investigate the holographic description of a superconductor constructed in the (2+1)-dimensional AdS soliton background in the probe limit. We study the holographic properties through both analytical and numerical methods. With analytical methods, we are the first to obtain the exact formula for critical phase transition points as $\mu_{c}=1+\sqrt{1+m^2}$. Around the transition points, we find a correspondence between the value of the scalar field at the tip and the scalar operator at infinity. We also generalize the front properties to holographic models in higher dimensional AdS soliton spacetime. Moreover, we examine effects of the scalar mass on stability of phase transitions with numerical methods. With $m^{2}\in (-0.38,0]$, we arrive at the classical second order insulator/superconductor phase transition. Surprisingly, there is no stable superconducting phases in cases of $m^{2}\in (-1,-0.38]$. In other words, superconductor only exists in a certain range of the scalar mass in the (2+1)-dimensional AdS soliton spacetime, which is very different from properties in other spacetime. 
Yan Peng
hep-th