Quantum critical response at the onset of spin-density-wave order in two-dimensional metals

Hartnoll, Sean A.; Hofman, Diego M.; Metlitski, Max A.; Sachdev, Subir

doi:10.1103/physrevb.84.125115

Cited by 79 publications

(112 citation statements)

References 72 publications

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“…For example, if the Fermi quasiparticles are coupled to a gapless boson (as is the case in many field-theoretical constructions of non-Fermi liquids; see e.g. [1,[54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] and references therein), small-momentum scattering is strongly preferred because of the larger phase space available to the gapless boson at smaller momenta. However, this small-momentum scattering does not degrade the current and so contributes differently to the conductivity than it does to the single-particle lifetime, meaning that the resistivity grows with temperature with a higher power than the single-particle scattering rate [64].…”

Section: Discussionmentioning

confidence: 99%

Charge transport by holographic Fermi surfaces

Faulkner

Iqbal²,

Liu

et al. 2013

Phys. Rev. D

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We compute the contribution to the conductivity from holographic Fermi surfaces obtained from probe fermions in an AdS charged black hole. This requires calculating a certain part of the one-loop correction to a vector propagator on the charged black hole geometry. We find that the current dissipation is as efficient as possible and the transport lifetime coincides with the single-particle lifetime. In particular, in the case where the spectral density is that of a marginal Fermi liquid, the resistivity is linear in temperature.

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Section: Discussionmentioning

confidence: 99%

Charge transport by holographic Fermi surfaces

Faulkner

Iqbal²,

Liu

et al. 2013

Phys. Rev. D

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“…It has recently been established [8,9] that the critical theory is strongly coupled in the physically important case of spatial dimension d = 2, with a breakdown of all the formal expansion methods of critical field theories. So accurate computations which can be quantitatively compared with experiments are presently out of reach.…”

Section: Introductionmentioning

confidence: 99%

Antiferromagnetism in metals: from the cuprate superconductors to the heavy fermion materials

Sachdev

Metlitski

Punk

2012

J. Phys.: Condens. Matter

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Abstract. The critical theory of the onset of antiferromagnetism in metals, with concomitant Fermi surface reconstruction, has recently been shown to be strongly coupled in two spatial dimensions. The onset of unconventional superconductivity near this critical point is reviewed: it involves a subtle interplay between the breakdown of fermionic quasiparticle excitations on the Fermi surface, and the strong pairing glue provided by the antiferromagnetic fluctuations. The net result is a logarithmsquared enhancement of the pairing vertex for generic Fermi surfaces, with a universal dimensionless co-efficient independent of the strength of interactions, which is expected to lead to superconductivity at the scale of the Fermi energy. We also discuss the possibility that the antiferromagnetic critical point can be replaced by an intermediate 'fractionalized Fermi liquid' phase, in which there is Fermi surface reconstruction but no long-range antiferromagnetic order. We discuss the relevance of this phase to the underdoped cuprates and the heavy-fermion materials.

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“…Strictly speaking these rates of order k B T /ħ h are at best on the boundary of a hydrodynamic regime describing momentum and Goldstone physics; in the quantum critical fan, σ(ω) should be computed from the effective long wavelength theory of the density wave quantum phase transition. While some computations of transport in a candidate quantum critical theory exist at T = 0 [65,66] and at ω = 0 [67, 68], the possibility of a peak in the optical conductivity at nonzero ω/T has not been considered. The peak location ω o will be sensitive both to the pinning of the pseudo-Goldstone mode and to the thermal gap generated in the quantum critical theory.…”

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confidence: 99%

Bad Metals from Fluctuating Density Waves

et al. 2017

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Bad metals have a large resistivity without being strongly disordered. In many bad metals the Drude peak moves away from zero frequency as the resistivity becomes large at increasing temperatures. We catalogue the position and width of the 'displaced Drude peak' in the observed optical conductivity of several families of bad metals, showing that ω peak ∼ ∆ω ∼ k B T /ħ h. This is the same quantum critical timescale that underpins the T -linear dc resistivity of many of these materials. We provide a unified theoretical description of the optical and dc transport properties of bad metals in terms of the hydrodynamics of short range quantum critical fluctuations of incommensurate density wave order. Within hydrodynamics, pinned translational order is essential to obtain the nonzero frequency peak. Check for updates doi:10.21468/SciPostPhys.3.3.025 Bad metals are defined by the fact that if their electrical resistivity is interpreted within a conventional Drude formalism, the corresponding mean free path of the quasiparticles is so short that the Boltzmann equation underlying Drude theory is not consistent [1][2][3]. As such, bad metals pose a long-standing challenge to theory. In this work we show that the hydrodynamics of phase-fluctuating charge density waves can lead to bad metallic behavior. Hydrodynamics is a tightly constrained formalism for the low energy and long wavelength dynamics of media [4,5]. Non-quasiparticle media, in particular, exhibit fast local thermalization leading to extended hydrodynamics regimes. Phase fluctuations in the density wave can be robustly incorporated into this description and will be essential in order for the states to be metallic, rather than insulating. We will use the hydrodynamic framework to explain observed dc and optical transport behavior that is common to several families of bad metal materials.Recent work has emphasized that the absence of quasiparticles is not sufficient to obtain a bad metal [6]. If the total momentum of the charge carriers is long-lived, then the resistivity will be small even if all single-particle excitations decay rapidly. The importance of the fate of momentum for transport has long been appreciated [7,8], but has acquired renewed relevance 1 SciPost Phys. 3, 025 (2017) in the context of modern unconventional metals, e.g. [9,10]. Two previously considered scenarios for removing the long-lived momentum (sound) mode from the collective description of charge transport are as follows. Firstly, that the low energy, non-quasiparticle, description of bad metals is strongly non-translationally invariant and hence momentum is absent from the hydrodynamic description [6]. Secondly, that an emergent particle-hole symmetry at low energies decouples charge transport from momentum [11]. These mechanisms do not seem to be at work in bad metals. The resistivity of bad metals is not typically strongly dependent on the strength of disorder and some bad metals appear to be relatively clean. Emergent particle-hole symmetry does not decouple momentum ...

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Quantum critical response at the onset of spin-density-wave order in two-dimensional metals

Cited by 79 publications

References 72 publications

Charge transport by holographic Fermi surfaces

Charge transport by holographic Fermi surfaces

Antiferromagnetism in metals: from the cuprate superconductors to the heavy fermion materials

Bad Metals from Fluctuating Density Waves

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