Lehigh University, Department of Physics, Bethlehem, PA 18015, USA
09.10.2026. u 14:00h
Institute of Physics, 1st wing lecture room & Zoom
From the Standard model for elementary particles to various quantum crystals, such as graphene, the dynamics of underlying fermionic degrees of freedom is governed by the Dirac Hamiltonian that manifestly preserves the Lorentz symmetry. In this talk, first I will propose a general principle of constructing non-Hermitian (NH) Lorentz invariant Dirac operator, featuring two velocity parameters vH and vNH, associated with the Hermitian and anti-Hermitian components of such operators, respectively. I will show that in such noninteracting systems, all the observables, such as the energy spectrum, density of states, and frequency dependent optical conductivity and shear viscosity are governed by an effective Fermi velocity vF=(vH 2- vH 2)1/2.
Next, I will consider interactions between NH Dirac quasiparticles and bosonic degrees of freedom, such as (a) the scalar order-parameter fluctuations mediated by short-range Hubbard-like repulsions, yielding Yukawa interactions and (b) relativistic helical photons, giving rise to NH quantum electrodynamics. In both scenarios, although the system primarily loses the Lorentz symmetry at the lattice or ultraviolet scale, it gains a NH Lorentz symmetry through various quantum loop corrections in the deep infrared regime in terms of a unique terminal velocity for all the participating degrees of freedom. I will briefly mention such a generic outcome for spin-3/2 NH birfringent Driac fermions.
If time permits, I will finally showcase the Hermitian extension of this construction in terms of hidden-ordered Dirac fermions, and highlight two phenomena, namely NH and inverse catalysis from lattice-based numerical self-consistent solutions for competing orders.
References:
- Juricic and B. Roy, Communications Physics 7, 169 (2024)
Sk A. Murshed and B. Roy, Journal of High Energy Physics 2024, 143 (2024)
Sk A. Murshed and B. Roy, SciPost Phys. 18, 073 (2025)
- Roy, arXiv:2606.27368
- A. Leong and B. Roy, Phys. Rev. B 113, 155152 (2026)
Join Zoom Meeting:
https://us06web.zoom.us/j/5081440931
Meeting ID: 508 144 0931
Seminar hosts: Juraj Krsnik i Borna Radatović