Latest Papers in Condensed Matter Physics

Statistical Mechanics

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An Extension of ETH to Non-Equilibrium Steady States (1811.03114v2)

Sanjay Moudgalya, Trithep Devakul, D. P. Arovas, S. L. Sondhi

2018-11-07

We extend the notion of the Eigenstate Thermalization Hypothesis (ETH) to Open Quantum Systems governed by the Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) Master Equation. We present evidence that the eigenstates of non-equilibrium steady state (NESS) density matrices obey a generalization of ETH in boundary-driven systems when the bulk Hamiltonian is non-integrable, just as eigenstates of Gibbs density matrices are conjectured to do in equilibrium. This generalized ETH, which we call NESS-ETH, can be used to obtain representative pure states that reproduce the expectation values of few-body operators in the NESS. The density matrices of these representative pure states can be further interpreted as weak solutions of the GKLS Master Equation. Additionally, we explore the validity and breakdown of NESS-ETH in the presence of symmetries, integrability and many-body localization in the bulk Hamiltonian.

Quantum Many-body Scars in a Landau Level on a Thin Torus (1906.05292v2)

Sanjay Moudgalya, B. Andrei Bernevig, Nicolas Regnault

2019-06-12

We study a kinetically constrained pair hopping model that arises within a Landau level in the quantum Hall effect. At filling , the model exactly maps onto the so-called ``PXP model", a constrained model for the Rydberg atom chain that is numerically known to exhibit ETH-violating states in the middle of the spectrum or quantum many-body scars. Indeed, particular charge density wave configurations exhibit the same revivals seen in the PXP model. We generalize the mapping to fillings factors , and show that the model is equivalent to non-integrable spin-chains within particular constrained Krylov Hilbert spaces. These lead to new examples of quantum many-body scars which manifest as revivals and slow thermalization of particular charge density wave states. Finally, we investigate the stability of the quantum scars under certain Hamiltonian perturbations motivated by the fractional quantum Hall physics.

Early-Time and Late-Time Quantum Chaos (1907.04289v1)

Chen-Te Ma

2019-07-09

We show the relation between the Heisenberg averaging of regularized two-points out-of-time ordered correlation function and the two-points spectral form factor in bosonic quantum mechanics. The generalization to all even-points is also discussed. We also do the direct extension from the bosonic quantum mechanics to the non-interacting scalar field theory through the oscillator languages. Finally, we find that the coherent state and large- approaches are useful in the late-time study. We find that the computation of the coherent state can be simplified by the Heisenberg averaging. Therefore, this provides a simplified way to probe the late-time quantum chaos through a coherent state. The large- result is also comparable to the numerical result in the large- quantum mechanics. This can justify that large- technique in bosonic quantum mechanics can really probe the late time, not the early time. Because the quantitative behavior of large- can be captured from the numerical result, the realization in experiments should be possible.

Fundamental limits to radiative heat transfer: the limited role of nanostructuring in the near field (1903.07968v3)

Prashanth S. Venkataram, Sean Molesky, Weiliang Jin, Alejandro W. Rodriguez

2019-03-16

In a complementary article, we exploited algebraic properties of Maxwell's equations and fundamental principles such as electromagnetic reciprocity and passivity, to derive fundamental limits to radiative heat transfer applicable in near- through far-field regimes. The limits depend on the choice of material susceptibilities and bounding surfaces enclosing arbitrarily shaped objects. In this article, we apply these bounds to two different geometric configurations of interest, namely dipolar particles or extended structures of infinite area in the near field of one another, and compare these predictions to prior limits. We find that while near-field radiative heat transfer between dipolar particles can saturate purely geometric "Landauer" limits, bounds on extended structures cannot, instead growing much more slowly with respect to a material response figure of merit, an "inverse resistivity" for metals, due to the deleterious effects of multiple scattering; nanostructuring is unable to overcome these limits, which can be practically reached by planar media at the surface polariton condition.

Heating rates in periodically driven strongly interacting quantum many-body systems (1907.04261v1)

Krishnanand Mallayya, Marcos Rigol

2019-07-09

We study heating rates in strongly interacting quantum lattice systems in the thermodynamic limit. Using a numerical linked cluster expansion, we calculate the energy as a function of the driving time and find a robust regime in which heating is exponential in time. The heating rates are shown to be in excellent agreement with Fermi's golden rule. We discuss the relationship between heating rates and, within the eigenstate thermalization hypothesis, the smooth function that characterizes the off-diagonal matrix elements of the drive operator in the eigenbasis of the static Hamiltonian. We show that such a function, in nonintegrable and (remarkably) integrable Hamiltonians, can be probed experimentally by studying heating rates as functions of the frequency of the drive.

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