On the Phase Behavior of Disordered Type-II Superconductors

Asle Sudbø, Anh Kiet Nguyen, J. Hove

Nandini Trivedi, Amit Ghosal, Mohit Randeria

Mi-Ji Liang, Yong-Feng Yang, Chen Cheng +1 more

We use the density-matrix renormalization group method to investigate the superconductor-insulator transition (SIT) in disordered quasi-one-dimensional systems. Focusing on the case of an interacting spinful Hamiltonian at quarter filling, we contrast the differences arising in the SIT when the parent noninteracting model features flat or dispersive bands. Furthermore, we unveil the critical disorder amplitude that triggers insulating behavior by comparing disorder distributions that preserve or not SU(2) symmetry. While scaling analysis suggests the transition be of a Berezinskii-Kosterlitz-Thouless type for all models (two lattices and two disorder types), only in the flat-band model with Zeeman-like disorder is the critical disorder nonvanishing. In this sense, the flat-band structure does strengthen superconductivity in the presence of attractive interactions. For both flat- and dispersive-band models, (i) in the presence of SU(2)-symmetric random chemical potentials, the disorder-induced transition is from superconductor to insulator of singlet pairs; (ii) for the Zeeman-type disorder, the transition is from superconductor to insulator of unpaired fermions. In all cases, our numerical results suggest no intermediate disorder-driven metallic phase.

Luca Dell’Anna

S. Mo, J. Hove, Asle Sudbø

We present results from large-scale Monte Carlo simulations on the full Ginzburg-Landau (GL) model, including fluctuations in the amplitude and the phase of the matter field, as well as fluctuations of the noncompact gauge field of the theory. From this we obtain a precise critical value of the GL parameter ${\ensuremath{\kappa}}_{\mathrm{tri}}$ separating a first-order metal-to-superconductor transition from a second-order one, ${\ensuremath{\kappa}}_{\mathrm{tri}}=(0.76\ifmmode\pm\else\textpm\fi{}0.04)/\sqrt{2}.$ This agrees surprisingly well with earlier analytical results based on a disorder theory of the superconductor to metal transition, where the value ${\ensuremath{\kappa}}_{\mathrm{tri}}=0.798/\sqrt{2}$ was obtained. To achieve this, we have done careful infinite volume and continuum limit extrapolations. In addition we offer an interpretation of ${\ensuremath{\kappa}}_{\mathrm{tri}},$ namely, that it is also the value separating type-I and type-II behavior.

B. Chatterjee, A. Taraphder