Bose metal: Gauge-field fluctuations and scaling for field-tuned quantum phase transitions

We extend our previous discussion of the Bose metal to the field-tuned case. We point out that the recent observation of the metallic state as an intermediate phase between the superconductor and the insulator in the field-tuned experiments on MoGe films is in perfect consistency with the Bose metal scenario. We establish a connection between general dissipation models and gauge-field fluctuations and apply this to a discussion of scaling across the quantum phase boundaries of the Bose metallic state. Interestingly, we find that the Bose metal scenario implies a possible two parameter scaling for resistivity across the Bose metal-insulator transition, which is remarkably consistent with the MoGe data. Scaling at the superconductor-metal transition is also proposed, and a phenomenolgical model for the metallic state is discussed. The effective action of the Bose metal state is described and its low energy excitation spectrum is found to be omega proportional tok(3).