Bielectron vortices in two-dimensional Dirac semimetals

TL;DR

This paper predicts the existence of bielectron vortices in two-dimensional Dirac semimetals, which are bound states of Dirac fermions that could lead to new quantum phenomena and explain experimental observations in graphene.

Contribution

It introduces a new type of quasiparticle, bielectron vortices, formed by Dirac fermions, independent of the interaction sign, with potential implications for Majorana physics and condensed matter experiments.

Findings

Bielectron vortices can form in 2D Dirac materials regardless of interaction sign.

These vortices are zero-energy, double-charged, and bosonic, enabling condensation.

Potential explanation for unexplained phenomena in gated graphene experiments.

Abstract

Searching for new states of matter and unusual quasiparticles in emerging materials and especially low-dimensional systems is one of the major trends in contemporary condensed matter physics. Dirac materials, which host quasiparticles which are described by ultrarelativistic Dirac-like equations, are of a significant current interest from both a fundamental and applied physics perspective. Here we show that a pair of two-dimensional massless Dirac-Weyl fermions can form a bound state independently of the sign of the inter-particle interaction potential, as long as this potential decays at large distances faster than Kepler's inverse distance law. This leads to the emergence of a new type of energetically-favourable quasiparticle: bielectron vortices, which are double-charged and reside at zero-energy. Their bosonic nature allows for condensation and may give rise to Majorana physics without invoking a superconductor. These novel quasiparticles arguably explain a range of poorly understood experiments in gated graphene structures at low doping.