Absence of a quantum limit to charge diffusion in bad metals

Pakhira, Nandan; McKenzie, Ross H.

doi:10.1103/physrevb.91.075124

Cited by 33 publications

(35 citation statements)

References 45 publications

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“…This is due to the sharp crossover between the Fermi liquid fixed point and the local moment fixed point in the strongly correlated regime. A similar nonmonotonic temperature dependence is seen in the electrical resistivity from DMFT calculations and in organic charge-transfer salts close to the Mott insulator [5,23,34].…”

Section: High-temperature Behaviorsupporting

confidence: 50%

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Shear viscosity of strongly interacting fermionic quantum fluids

Pakhira

McKenzie

2015

Phys. Rev. B

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Eighty years ago, Eyring proposed that the shear viscosity of a liquid η has a quantum limit η n where n is the density of the fluid. Using holographic duality and the anti-de Sitter/conformal field theory correspondence in string theory, Kovtun, Son, and Starinets (KSS) conjectured a universal bound η s 4πk B for the ratio between the shear viscosity and the entropy density s. Using dynamical mean-field theory, we calculate the shear viscosity and entropy density for a fermionic fluid described by a single-band Hubbard model at half-filling. Our calculated shear viscosity as a function of temperature is compared with experimental data for liquid 3 He. At low temperature, the shear viscosity is found to be well above the quantum limit and is proportional to the characteristic Fermi liquid 1/T 2 dependence, where T is the temperature. With increasing temperature and interaction strength U , there is significant deviation from the Fermi liquid form. Also, the shear viscosity violates the quantum limit near the crossover from coherent quasiparticle-based transport to incoherent transport (the bad metal regime). Finally, the ratio of the shear viscosity to the entropy density is found to be comparable to the KSS bound for parameters appropriate to liquid 3 He. However, this bound is found to be strongly violated in the bad metal regime for parameters appropriate to lattice electronic systems such as organic charge-transfer salts.

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Section: High-temperature Behaviorsupporting

confidence: 50%

“…We found [23] clear violation of this bound in the strong coupling (bad metal) regime of the Hubbard model. In this paper, we calculate the shear viscosity in a single-band Hubbard model and explore possible violations of the conjectured quantum bounds on η and η/s.…”

Section: Introductionmentioning

confidence: 88%

Shear viscosity of strongly interacting fermionic quantum fluids

Pakhira

McKenzie

2015

Phys. Rev. B

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“…At half-filling this agrees with the idea of the system becoming more incompressible (χ c going to zero) as we approach the Mott insulating phase. 58 It is worth noting that an analytic calculation of χ c from equation (7) is complicated because n has a dependence on the double occupancy d (due to the d-dependence of q and λ (2) ), and the derivative against µ of the latter turns out to be difficult to calculate from equation (8). Figure 6.…”

Section: Charge Compressibilitymentioning

confidence: 99%

“…Charge compressibility χc as a function of temperature for the semicircular DOS, using slave-boson (solid line) and DMFT (dashed line) calculations from Ref. [58]. The bandwidth W is used as an energy scale in order to make the comparison easier.…”

Section: Charge Compressibilitymentioning

confidence: 99%

Low quasiparticle coherence temperature in the one-band Hubbard model: A slave-boson approach

Mezio

McKenzie

2017

Phys. Rev. B

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We use the Kotliar-Ruckenstein slave-boson formalism to study the temperature dependence of paramagnetic phases of the one-band Hubbard model for a variety of band structures. We calculate the Fermi liquid quasiparticle spectral weight Z and identify the temperature at which it decreases significantly to a crossover to a bad metal region. Near the Mott metal-insulator transition, this coherence temperature T coh is much lower than the Fermi temperature of the uncorrelated Fermi gas, as is observed in a broad range of strongly correlated electron materials. After a proper rescaling of temperature and interaction, we find a universal behavior that is independent of the band structure of the system. We obtain the temperature-interaction phase diagram as function of doping, and we compare the temperature dependence of the double occupancy, entropy, and charge compressibility with previous results obtained with Dynamical Mean-Field Theory. We analyse the stability of the method by calculating the charge compressibility.

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“…First, the diffusion bound can be violated in various situations [7][8][9][10]. Second, some strange metals are relatively clean and their thermoelectric effect may not be especially small.…”

Section: Introductionmentioning

confidence: 99%

Collective diffusion and quantum chaos in holography

Wang

et al. 2018

Phys. Rev. D

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We define a particular combination of charge and heat currents that is decoupled with the heat current. This "heat-decoupled" (HD) current can be transported by diffusion at long distances, when some thermoelectric conductivities and susceptibilities satisfy a simple condition. Using the diffusion condition together with the Kelvin formula, we show that the HD diffusivity can be same as the charge diffusivity and also the heat diffusivity. We illustrate that such mechanism is implemented in a strongly coupled field theory, which is dual to a Lifshitz gravity with the dynamical critical index z ¼ 2. In particular, it is exhibited that both charge and heat diffusivities build the relationship to the quantum chaos. Moreover, we study the HD diffusivity without imposing the diffusion condition. In some homogeneous holographic lattices, it is found that the diffusivity/chaos relation holds independently of any parameters, including the strength of momentum relaxation, chemical potential, or temperature. We also show a counter example of the relation and discuss its limited universality.

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Absence of a quantum limit to charge diffusion in bad metals

Cited by 33 publications

References 45 publications

Shear viscosity of strongly interacting fermionic quantum fluids

Shear viscosity of strongly interacting fermionic quantum fluids

Low quasiparticle coherence temperature in the one-band Hubbard model: A slave-boson approach

Collective diffusion and quantum chaos in holography

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