[hep-th] seminar u petak, 24. oktobra

[Maja Buric]

Pozdrav GPF grupi,

the next GPF seminar will be given by Vladimir Juricic on Friday 24th of 
October at 11.15, small seminar room on the second floor, at the IPB.


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


Abstract: 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.


Vidimo se, Maja