Electron pairing with gapless excitations in mixed double layers

TL;DR

This paper investigates interlayer pairing in mixed 2D electronic systems with different spectra, revealing complex quasiparticle spectra with deformed Dirac cones and unique density of states features.

Contribution

It introduces a mean-field analysis of interlayer pairing in mixed relativistic and non-relativistic 2D systems, highlighting the impact on quasiparticle spectra and band deformation.

Findings

Quasiparticle spectrum exhibits deformed Dirac cones near band touching points.

Band deformation leads to van Hove singularities in the density of states.

The phase difference of order parameter components influences the spectrum shape.

Abstract

We study the interlayer pairing states in layered systems of two different 2d electronic subsystems, one with relativistic linear and the other with non-relativistic parabolic spectrum. The complex order parameter of the paired state has a two component structure. We investigate the pairing state formation on the mean-field level, determine the critical interaction strength and evaluate the effective potential. The anisotropic three-band spectrum of quasiparticles depends explicitly on the phase difference of the order parameter components, rotates in momentum space as it changes. It is subject to the strong band deformation due to the pairing. It leads to the fusion and hybridization of initially decoupled bands. The quasiparticle spectrum has the shape of deformed Dirac cones in the vicinity of the two touching points between neighboring bands. The density of states exhibits a number of specific features due to band deformation, such as a van Hove singularity.