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

Abstract

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 in tact. In the vicinity of 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. In addition, we also show that the metallic state remains intact in the presence of Ohmic dissipation in spite of recent claims to the contrary. 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 the recent experiments on vortex glass systems in which the linear resistivity remained non-zero below the putative vortex glass transition and the experiments on thin films in which a metallic phase has been observed to disrupt the direct transition from a superconductor to an insulator.

Disorder-induced superconductor to insulator transition and finite phase stiffness in two-dimensional phase-glass models

“…The phase-glass model with a Gaussian distribution of disorder with nonzero mean has been studied in detail analytically, and the glass state found for larger disorder was shown to correspond to a Bose metal, within a mean-field theory approach [10][11][12]. This result and its extension to the magnetic field-tuned transition [27] provide a compelling description of experiments showing metallic behavior in superconducting thin films [13][14][15]28], in terms of a minimum model with glassy behavior [29]. However, although results from meanfield theory tend to agree with those for models with infinite range interactions or in high dimensions, they are usually not reliable for low-dimensional systems with short-range interactions.…”

How magnetic field can transform a superconductor into a Bose metal

“…Due to their small size, their spectrum does not experience Landau quantization and hence provides a reservoir of low energy states for the metallic transport. This alternative also provides a mechanism for Bose metal other than the exotic proposal of quantum phase glass [23,24], where the Josephson coupling constant is random in sign in the latter proposal. The anomalous metallic state described in the present paper possesses some of the features observed in the stripeordered LBCO [4] and the indium oxide films [7].…”

Theoretical analysis of drag resistance in amorphous thin films exhibiting superconductor-insulator transitions

“…39 argued against these results and obtained infinite conductance instead. This analysis has recently been extended to include the external perpendicular magnetic field, 38 which is more relevant to the experiments on the magnetic field tuned transition. However, Ref.…”