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Journal Article

Collisionless Transport Close to a Fermionic Quantum Critical Point in Dirac Materials

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Roy,  Bitan
Max Planck Institute for the Physics of Complex Systems, Max Planck Society;

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1801.03495.pdf
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Citation

Roy, B., & Juricic, V. (2018). Collisionless Transport Close to a Fermionic Quantum Critical Point in Dirac Materials. Physical Review Letters, 121(13): 137601. doi:10.1103/PhysRevLett.121.137601.


Cite as: https://hdl.handle.net/21.11116/0000-0002-6811-6
Abstract
Quantum transport close to a critical point is a fundamental, but enigmatic problem due to fluctuations, persisting at all length scales. We report the scaling of optical conductivity (OC) in the collisionless regime ((sic)omega >> k(B)T) in the vicinity of a relativistic quantum critical point, separating two-dimensional (d = 2) massless Dirac fermions from a fully gapped insulator or superconductor. Close to such a critical point, gapless fermionic and bosonic excitations are strongly coupled, leading to a universal suppression of the interband OC as well as of the Drude peak (while maintaining its delta function profile) inside the critical regime, which we compute to the leading order in 1/N-f- and epsilon expansions, where N-f counts the fermion flavor number and epsilon = 3 - d. Correction to the OC at such a non-Gaussian critical point due to the longrange Coulomb interaction and generalizations of these scenarios to a strongly interacting three-dimensional Dirac or Weyl liquid are also presented, which can be tested numerically and possibly from nonperturbative gauge-gravity duality, for example.