Vladimir Juričić, NORDITA, the Nordic Institute for Theoretical Physics, Stockholm, Sweden

Optical conductivity in the interacting two-dimensional nodal semimetals

Dirac and Weyl semimetals feature pseudorelativistic linearly dispersing excitations which give rise to universal signatures in optical conductivity. They are stable for weak electron-electron interactions due to a vanishing density of states at the nodal point. At a strong interaction, however, they can undergo a plethora of quantum phase transitions into various insulating and superconducting states. In particular, two-dimensional (2D) non-Fermi liquid emerging from the underlying strongly-coupled quantum critical point lacks sharp quasiparticle excitations, and is thus difficult to probe. I will show that the linear optical conductivity in the collisionless regime can play a pivotal role in this regard [1]. More specifically, a universal suppression of both the inter-band optical conductivity and the Drude peak occurs in such a non-Fermi liquid due to the strongly coupled gapless fermionic and bosonic excitations. In a tilted 2D nodal semimetal, a short-range Coulomb interaction leads to a line of critical points controlled by the tilting. As I will show, the nonlinear Hall conductivity even in a noninteracting 2D tilted Dirac semimetal exhibits interesting features, such as the tilt-driven splitting of the resonances. Finally, the nonlinear Hall conductivity gets suppressed in a non-Fermi liquid emerging from the line of the quantum-critical points and can be used to distinguish this state from its tilt-free counterpart [2].


  • [1] B. Roy and V Juričić, Phys. Rev. Lett.  121, 137601 (2018).
  • [2] H. Rostami and V Juričić, Phys. Rev. Research 2, 013069 (2020).

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