@article { ISI:000530026700003,
title = {Drag viscosity of metals and its connection to Coulomb drag},
journal = {Phys. Rev. B},
volume = {101},
number = {19},
year = {2020},
month = {MAY 4},
pages = {195106},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {Recent years have seen a surge of interest in studies of hydrodynamic transport in electronic systems. We investigate the electron viscosity of metals and find a component that is closely related to Coulomb drag. By using linear-response theory, viscosity, which is a transport coefficient for momentum, can be extracted from the retarded correlation function of the momentum flux, i.e., the stress tensor. There exists a previously overlooked contribution to the shear viscosity from the interacting part of the stress tensor which accounts for the momentum flow induced by interactions. This contribution, which we dub drag viscosity, is caused by the frictional drag force due to long-range interactions. It is therefore linked to Coulomb drag which also originates from the interaction-induced drag force. Starting from the Kubo formula and using the Keldysh technique, we compute the drag viscosity of two- and three-dimensional metals along with the drag resistivity of double-layer two-dimensional electronic systems. Both the drag resistivity and drag viscosity exhibit a crossover from quadraticin-T behavior at low temperatures to a linear behavior at higher temperatures. Although the drag viscosity appears relatively small compared with the normal Drude component for the clean metals, it may dominate hydrodynamic transport in some systems, which are discussed in the conclusion.},
issn = {2469-9950},
doi = {10.1103/PhysRevB.101.195106},
author = {Liao, Yunxiang and Galitski, Victor}
}
@article { ISI:000505981500001,
title = {Many-body localization landscape},
journal = {Phys. Rev. B},
volume = {101},
number = {1},
year = {2020},
month = {JAN 6},
pages = {014201},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We generalize the notion of {\textquoteleft}{\textquoteleft}localization landscape,{{\textquoteright}{\textquoteright}} introduced by M. Filoche and S. Mayboroda {[}Proc. Natl. Acad. Sci. USA 109, 14761 (2012)] for the single-particle Schrodinger operator, to a wide class of interacting many-body Hamiltonians. The many-body localization landscape (MBLL) is defined on a graph in the Fock space, whose nodes represent the basis vectors in the Fock space and edges correspond to transitions between the nodes connected by the hopping term in the Hamiltonian. It is shown that in analogy to the single-particle case, the inverse MBLL plays the role of an effective potential in the Fock space. We construct a generalized discrete Agmon metric and prove Agmon inequalities on the Fock-state graph to obtain bounds on the exponential decay of the many-body wave functions in the Fock space. The corresponding construction is motivated by the semiclassical WKB approximation, but the bounds are exact and fully quantum mechanical. We then prove a series of locality theorems which establish where in the Fock space we expect eigenstates to localize. Using these results as well as the locator expansion, we establish evidence for the existence of many-body localized states for a wide class of lattice models in any physical dimension in at least a part of their Hilbert space. The key to this argument is the observation that in sharp contrast to the conventional locator expansion for the Green{\textquoteright}s function, the locator expansion for the landscape function contains no resonances. For short-range hopping, which limits the connectivity of the Fock-state graph, the locator series is proven to be convergent and bounded by a simple geometric series. This, in combination with the discrete Agmon-type inequalities and the locality theorems, shows that localization for a fraction of the Hilbert space survives weak interactions and weak hopping at least for some realizations of disorder, but cannot prove or rule out localization of the entire Hilbert space. We qualitatively discuss potential breakdown of the locator expansion in the MBLL for long-range hopping and the appearance of a mobility edge in higher-dimensional theories.},
issn = {2469-9950},
doi = {10.1103/PhysRevB.101.014201},
author = {Balasubramanian, Shankar and Liao, Yunxiang and Galitski, Victor}
}
@article {ISI:000478991700001,
title = {Critical viscosity of a fluctuating superconductor},
journal = {Phys. Rev. B},
volume = {100},
number = {6},
year = {2019},
month = {AUG 2},
pages = {060501},
publisher = {AMER PHYSICAL SOC},
type = {Article},
abstract = {We consider a fluctuating superconductor in the vicinity of the transition temperature, T-c. The fluctuation shear viscosity is calculated. In two dimensions, the leading correction to viscosity is negative and scales as delta eta(T) alpha ln(T - T-c). Critical hydrodynamics of the fluctuating superconductor involves two fluids: a fluid of fluctuating pairs and a quasiparticle fluid of single-electron excitations. The pair viscosity (Aslamazov-Larkin) term is shown to be zero. The (density of states) correction to viscosity of single-electron excitations is negative, which is due to fluctuating pairing that results in a reduction of electron density. Scattering of electrons off of the fluctuations gives rise to an enhanced quasiparticle scattering and another (Maki-Thomson) negative correction to viscosity. Our results suggest that fluctuating superconductors provide a promising platform to investigate low-viscosity electronic media and may potentially host fermionic/electronic turbulence. Some experimental probes of two-fluid critical hydrodynamics are proposed such as time-of-flight measurement of turbulent energy cascades in critical cold atom superfluids and magnetic dynamos in three-dimensional fluctuating superconductors.},
issn = {2469-9950},
doi = {10.1103/PhysRevB.100.060501},
author = {Liao, Yunxiang and Galitski, Victor}
}
@article { ISI:000450139700007,
title = {Nonlinear sigma model approach to many-body quantum chaos: Regularized and unregularized out-of-time-ordered correlators},
journal = {PHYSICAL REVIEW B},
volume = {98},
number = {20},
year = {2018},
month = {NOV 14},
pages = {205124},
issn = {2469-9950},
doi = {10.1103/PhysRevB.98.205124},
author = {Liao, Yunxiang and Galitski, Victor}
}