[institut] [phys4phys] GPF seminar, 24th October

[Maja Buric]

Dear colleagues,

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.



Link:
https://gravityserver.ipb.ac.rs/b/mar-ae0-f4q-qww


Best regards,
Maja Buric
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