Transport in Inhomogeneous Quantum Critical Fluids and in the Dirac Fluid in Graphene
Fig. 3* [Reprinted by permission from American Physical Society ©2016]
In a recent paper in Physical Review B, graduate students Andrew Lucas and Jesse Crossno, Kin Chung Fong from Raytheon BBN Technologies, and professors Philip Kim and Subir Sachdev describe developing a general hydrodynamic framework for computing direct current, thermal, and electric transport in a strongly interacting finite-temperature quantum system near a Lorentz-invariant quantum critical point. This framework is nonperturbative in the strength of long-wavelength fluctuations in the background-charge density of the electronic fluid and requires the rate of electron-electron scattering to be faster than the rate of electron-impurity scattering. The scientists use this formalism to compute transport coefficients in the Dirac fluid in clean samples of graphene near the charge neutrality point, and find results insensitive to long-range Coulomb interactions. They then compare the numerical results to recent experimental data on thermal and electrical conductivity in the Dirac fluid in graphene and find a substantially improved quantitative agreement over existing hydrodynamic theories. They further comment on the interplay between the Dirac fluid and acoustic and optical phonons, and qualitatively explain the experimentally observed effects. The team believes their work paves the way for quantitative contact between experimentally realized condensed matter systems and the wide body of high-energy inspired theories on transport in interacting many-body quantum systems.
*See A. Lucas, J. Crossno, K.C. Fong, P. Kim, and S. Sachdev, "Transport in inhomogeneous quantum critical fluids and in the Dirac fluid in graphene," Physical Review B 93, 075426 | DOI: http://dx.doi.org/10.1103/PhysRevB.93.075426.