Engineering Weyl nodes in Dirac semimetals by a magnetic field

TL;DR

This paper explores how applying a magnetic field to Dirac semimetals induces a phase transition from a gapped state to a Weyl semimetal with separated Weyl nodes, driven by a dynamically generated chiral shift.

Contribution

It demonstrates the emergence of Weyl nodes in Dirac semimetals under magnetic fields through a phase transition involving chiral symmetry breaking.

Findings

Existence of a critical chemical potential for phase transition.

Formation of Weyl nodes with a chiral shift aligned with the magnetic field.

Rearrangement of the Fermi surface during the transition.

Abstract

We study the phase diagram of a Dirac semimetal in a magnetic field at a nonzero charge density. It is shown that there exists a critical value of the chemical potential at which a first-order phase transition takes place. At subcritical values of the chemical potential the ground state is a gapped state with a dynamically generated Dirac mass and a broken chiral symmetry. The supercritical phase is the normal (gapless) phase with a nontrivial chiral structure: it is a Weyl semimetal with a pair of Weyl nodes for each of the original Dirac points. The nodes are separated by a dynamically induced chiral shift. The direction of the chiral shift coincides with that of the magnetic field and its magnitude is determined by the quasiparticle charge density, the strength of the magnetic field, and the strength of the interaction. The rearrangement of the Fermi surface accompanying this phase transition is described.