Measuring Hall viscosity of graphene’s electron fluid

Berdyugin, A. I.; Xu, Shuigang; Pellegrino, Francesco; Kumar, Roshan Krishna; Principi, Alessandro; Torre, Iacopo; Shalom, M. Ben; Taniguchi, Takashi; Watanabe, Kenji; Grigorieva, I. V.; Polini, Marco; Geǐm, A. K.; Bandurin, Denis

doi:10.1126/science.aau0685

Cited by 287 publications

(274 citation statements)

References 41 publications

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“…Since ee ∼ T −2 , the effect should be more pronounced at lower temperatures (if hydrodynamics is valid). This effect has been observed experimentally in narrow channels [19].…”

Section: A Narrow Channelsupporting

confidence: 67%

“…It was recently suggested [17] that viscous electron flow through an inhomogeneous device would lead to negative magnetoresistance in a (quasi-)two-dimensional metal, where the dissipative resistivity decreases as one turns on a small magnetic field: ∂ρ/∂(B 2 ) < 0. Indeed, this effect has been observed in GaAs [18], as well as in very narrow channels of graphene [19]. Later, [20,21] pointed out that in bulk crystals, the magnetoresistance would always be positive; however, their argument is perturbative in the strength of the inhomogeneity.…”

Section: Introductionmentioning

confidence: 96%

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Sign of viscous magnetoresistance in electron fluids

Mandal

Lucas

2020

Phys. Rev. B

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In sufficiently clean metals, it is possible for electrons to collectively flow as a viscous fluid at finite temperature. These viscous effects have been predicted to give a notable magnetoresistance, but whether the magnetoresistance is positive or negative has been debated. We argue that regardless of the strength of inhomogeneity, bulk magnetoresistance is always positive in the hydrodynamic regime. We also compute transport in weakly inhomogeneous metals across the ballistic-to-hydrodynamic crossover, where we also find positive magnetoresistance. The non-monotonic temperature dependence of resistivity in this regime (a bulk Gurzhi effect) rapidly disappears upon turning on any finite magnetic field, suggesting that magnetotransport is a simple test for viscous effects in bulk transport, including at the onset of the hydrodynamic regime.

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“…Since ee ∼ T −2 , the effect should be more pronounced at lower temperatures (if hydrodynamics is valid). This effect has been observed experimentally in narrow channels [19].…”

Section: A Narrow Channelsupporting

confidence: 67%

Section: Introductionmentioning

confidence: 96%

Sign of viscous magnetoresistance in electron fluids

Mandal

Lucas

2020

Phys. Rev. B

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“…In this section we provide a validation of this numerical approach by simulating steady-state flows in the so-called "vicinity-geometry", which has been subject of several theoretical and experimental studies [98][99][100] to outline phenomena such as negative nonlocal resistance, current whirlpools, and measuring the Hall viscosity of graphene's electrons fluid. The geometrical setup is sketched in Fig.…”

Section: Hydrodynamic Flow Of Electrons In Graphenementioning

confidence: 99%

Relativistic lattice Boltzmann methods: Theory and applications

et al. 2020

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We present a systematic account of recent developments of the relativistic Lattice Boltzmann method (RLBM) for dissipative hydrodynamics. We describe in full detail a unified, compact and dimension-independent procedure to design relativistic LB schemes capable of bridging the gap between the ultra-relativistic regime, k B T mc 2 , and the non-relativistic one, k B T mc 2 . We further develop a systematic derivation of the transport coefficients as a function of the kinetic relaxation time in d = 1, 2, 3 spatial dimensions. The latter step allows to establish a quantitative bridge between the parameters of the kinetic model and the macroscopic transport coefficients. This leads to accurate calibrations of simulation parameters and is also relevant at the theoretical level, as it provides neat numerical evidence of the correctness of the Chapman-Enskog procedure. We present an extended set of validation tests, in which simulation results based on the RLBMs are compared with existing analytic or semi-analytic results in the mildly-relativistic (k B T ∼ mc 2 ) regime for the case of shock propagations in quark-gluon plasmas and laminar electronic flows in ultra-clean graphene samples. It is hoped and expected that the material collected in this paper may allow the interested readers to reproduce the present results and generate new applications of the RLBM scheme.

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“…Transport in metals is usually dominated by MR scattering which results in a diffusive Ohmic regime. A novel hydrodynamic regime with collective fluid-like behavior, found in graphene [24][25][26][27], (Ga,Al)As [28][29][30] and other select materials [31][32][33][34], can arise when MR scattering is weak and MC scattering is strong. We show that the transition from an Ohmic to a hydrodynamic regime can be readily tuned to occur through the fluctuation-dominated ballistic regime, realizing a QCP-mediated nonequilibrium transition.…”

mentioning

confidence: 99%

Hydrodynamic and ballistic AC transport in two-dimensional Fermi liquids

et al. 2019

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Electronic transport in Fermi liquids is usually Ohmic, because of momentum-relaxing scattering due to defects and phonons. These processes can become sufficiently weak in two-dimensional materials, giving rise to either ballistic or hydrodynamic transport, depending on the strength of electron-electron scattering. We show that the ballistic regime is a quantum critical point (QCP) on the regime boundary separating Ohmic and hydrodynamic transport. The QCP corresponds to a free conformal field theory (CFT) with a dynamical scaling exponent z = 1. Its nontrivial aspects emerge in device geometries with shear, wherein the regime has an intrinsic universal dissipation, a nonlocal current-voltage relation, and exhibits the critical scaling of the underlying CFT. The Fermi surface has electron-hole pockets across all angular scales and the current flow has vortices at all spatial scales. We image the fluctuations in high-definition and animate their emergence as experimental parameters are tuned to the QCP a . The vortices clearly demonstrate that Pauli exclusion alone can produce collective effects, with low-frequency AC transport mediated by vortex dynamics b . The scale-invariant spatial structure is much richer than that of an interaction-dominated hydrodynamic regime, which only has a single vortex at the device scale. Our findings provide a theoretical framework for both interaction-free and interaction-dominated non-Ohmic transport in two-dimensional materials, as seen in several contemporary experiments. a Spatial fluctuations: https://vimeo.com/365020115 , Fermi surface fluctuations: https://vimeo.com/ 364982637 b Vortex dynamics and frequency crossover: https://vimeo.com/366725650Quantum critical points (QCP) mediate second-order quantum phase transitions (QPT), produced by tuning non-thermal parameters such as doping, magnetic field or pressure. Systems at QCPs obey universal scaling, and are dominated by quantum fluctuations [1]. A prototypical QPT occurs in the 1D quantum Ising model in a transverse magnetic field, realized in CoNb 2 O 6 [2]. As the external field is increased, the ground state changes from an ordered phase set by exchange interaction to a field-aligned quantum paramagnet. The transition occurs through a QCP with a dynamical scaling exponent z = 1, which connects the correlation length ξ and time τ via τ ∝ ξ z . Remarkably, the ubiquitous Fermi liquid hosts exactly such a QCP in the form of free fermions; a Fermi gas. Absent all interactions, gapless quasiparticles on the Fermi surface obey a relativistic free-field conformal field theory (CFT), with the speed of light set by the Fermi velocity v F [3]. This simple CFT exhibits critical scaling with z = 1. Microscopic interactions are indeed irrelevant, as expected at criticality, because there are none.Although a Fermi gas obeys critical scaling [4], it is never pictured as a QCP. The singleparticle Green's function has a simple pole, not a branch cut characteristic of interacting QCPs [5]; it is unclear how and where critical fluctuatio...

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Measuring Hall viscosity of graphene’s electron fluid

Cited by 287 publications

References 41 publications

Sign of viscous magnetoresistance in electron fluids

Sign of viscous magnetoresistance in electron fluids

Relativistic lattice Boltzmann methods: Theory and applications

Hydrodynamic and ballistic AC transport in two-dimensional Fermi liquids

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