Abstract
The authors use effective low-energy theories involving Dirac composite fermions to investigate the effects of a dissipative Coulomb interaction on certain superconductor-insulator and integer quantum Hall transitions in the presence of quenched randomness in two spatial dimensions. The paper shows how composite fermions provide a unifying framework for various diffusive quantum critical points.
Highlights
Delocalization transitions determine the phase diagrams of various electronic systems [1,2,3]
We study the effects of quenched disorder and a dissipative Coulomb interaction on the critical properties of two such models
While it is clear that the Dirac mass is even under C, it is less obvious that perturbation by ψψ is time-reversal invariant
Summary
Delocalization transitions determine the phase diagrams of various electronic systems [1,2,3]. Using the large Nf expansion, we reexamine these works and extend them to include the effects of a dissipative Coulomb interaction (Sec. II C) and “topological disorder” (Sec. II D), generally confirming prior results that found interacting, diffusive fixed points for certain types of disorder. A capacitively coupled screening plane has been found to affect the metallic behavior in thin films [46], lifting an anomalous lowtemperature metallic regime that intervenes a direct magnetic field-tuned SIT To investigate such effects, we consider a Coulomb interaction that is screened by a diffusive twodimensional Fermi gas [47]. Our result differs from that of Vishwanath, Moore, and Senthil [47], who studied the effects of a dissipative Coulomb interaction on the dirty XY model using the double- expansion and found a line of fixed points with z = 1 and continuously varying ν. Of other types of disorder on the theories in (1.4) [and (1.2)] when a dissipative Coulomb interaction is present
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