IPB

др Владимир Јуричић

23. октобра 2025.

У оквиру семинара Групе за гравитацију, честице и поља, у петак, 24. октобра 2025. године у 11:15 у сали 360 Института за физику у Београду, др Владимир Јуричић одржаће предавање:

Non-Hermitian Dirac Matter:  Yukawa-Lorentz symmetry and exceptional magic angles 

САЖЕТАК:

In this talk, we will discuss the emergence of non-Hermitian (NH) Dirac materials when Dirac systems interact with the environment. We first introduce a general framework for constructing symmetry-protected, Lorentz-invariant NH Dirac semimetals featuring real or imaginary linear band dispersions and vanishing density of states [1]. Short-range (Hubbard-type) interactions drive quantum phase transitions
to gapped orders via an intermediate quantum-critical, non-Fermi-liquid regime.  Depending on the Clifford algebra between NH Dirac operators and candidate mass orders, the renormalization group flows either to an NH fixed point or to a restored-Hermitian one, while generically exhibiting an emergent Yukawa–Lorentz symmetry with a unique Fermi velocity shared by fermionic and bosonic modes. We further discuss the role of tilt in NH Dirac systems via its observable consequences and interaction effects [2].

Turning to moiré platforms, a generalized Bistritzer–MacDonald theory of NH twisted bilayer graphene uncovers two kinds of magic angles: exceptional angles, marking real-to-imaginary spectral transitions (exceptional points), and a distinct Hermitian angle where only the real Fermi velocity vanishes while the imaginary part is maximal, representing an NH analogue of the Hermitian magic angle [3]. Finally, we discuss a general principle for the emergence of exceptional flat bands in NH bipartite lattices [4].

[1] V. J., B. Roy, Communications Physics 7, 169 (2024).
[2] S. Pino-Alarcon, V. J., Phys. Rev. B 111, 195126 (2025).
[3] J. P. Esparza, V. J., Phys. Rev. Lett. 134, 226602 (2025)
[4] J. P. Esparza, V. J., arXiv:2508.10901.