A quantum phase transition in d-wave superconductors and symmetry features of quasi-one-dimensional superconductors

I. Ţifrea, D. Bodea, I. Grosu +1 more

We consider the fluctuation conductivity in the critical region of a disorder induced quantum phase transition in layered d-wave superconductors. We specifically address the fluctuation contribution to the system’s conductivity in the limit of large (quasi-two-dimensional system) and small (quasi-three-dimensional system) separation between adjacent layers of the system. Both in-plane and c-axis conductivities were discussed near the point of insulator-superconductor phase transition. The value of the dynamical critical exponent, z = 2, permits a perturbative treatment of this quantum phase transition under the renormalization group approach. We discuss our results for the system conductivities in the critical region as function of temperature and disorder.

Matthias Vojta C, Subir Sachdev A

Xiao Liang, Moe Key

With the coupled Dyson-Schwinger equations in the framework of the unified QED3 theory,we study the phase transition between the antiferromagnet(AF) and the d-wave superconductor (dSC) of planar cuprates at T=0.By solving the coupled Dyson-Schwinger equations both analytically and numerically in rainbow approximation in Landau gauge and comparing the obtained results with that given in the 1/N expansion,we find that there exists a chiral symmetry breaking from dSC phase to AF phase when the quasi- fermion flavors N■4 in half-filling and the AF phase can possibly coexist with the dSC phase in the underdoped region.By comparing the pressure between the coexistent AF-dSC phase and dSC phase,we find that AF-dSC coexisting phase is the stable phase,the AF phase can then coexist with the dSC phase.

Wei Zhang, Carlos A. R. Sá de Melo

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.

N. Bergeal, Johan Biscaras, Simon Hurand +6 more