Vortex glass is a metal: Unified theory of the magnetic-field and disorder-tuned Bose metals

We consider the disordered quantum rotor model in the presence of a magnetic field. We analyze the transport properties in the vicinity of the multicritical point between the superconductor, phase glass, and paramagnetic phases. We find that the magnetic field leaves metallic transport of bosons in the glassy phase intact. In the vicinity of the superconductivity-to-Bose metal transition, the resistitivy turns on as (H- Hc) 2 with Hc. This functional form is in excellent agreement with the experimentally observed turn-on of the resistivity in the metallic state in MoGe -namely, R≈ Rc (H- Hc) μ, 1<μ<3. The metallic state is also shown to presist in three spatial dimensions. As the phase glass in d=3 is identical to the vortex glass, we conclude that the vortex glass is, in actuality, a metal rather than a superconductor at T=0. Our analysis unifies recent experiments on vortex glass systems in which the linear resistivity remained nonzero below the putative vortex glass transition and experiments on thin films in which a metallic phase has been observed to disrupt the direct transition from a superconductor to an insulator.