Viscous electron flow in mesoscopic two-dimensional electron gas

Gusev, G. M.; Levin, A. D.; Levinson, E. V.; Bakarov, A. K.

doi:10.1063/1.5020763

Cited by 109 publications

(95 citation statements)

References 21 publications

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“…At the same time investigating charge transport in the buried electron gas on a microscopic level is cumbersome. Therefore little is known about the electrons microscopic behavior and there are surprises like the strongly viscous behavior of charge carriers in high-mobility electron systems [1][2][3][4].…”

Section: Introduction To Branched Electron Flow and Scanning Gate Micmentioning

confidence: 99%

Stable branched electron flow

et al. 2018

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The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of ballistic electron trajectories. The details of the pattern are determined by the correlated potential of remote dopants with an amplitude far below the Fermi energy. We find that the pattern persists even if the electron density is significantly reduced such that the change in Fermi energy exceeds the background potential amplitude. The branch pattern is robust against changes in charge carrier density, but not against changes in the background potential caused by additional illumination of the sample.

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Section: Introduction To Branched Electron Flow and Scanning Gate Micmentioning

confidence: 99%

Stable branched electron flow

et al. 2018

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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.…”

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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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“…Historically such metals did not exist: in a Fermi liquid, the electron-impurity scattering rate is always faster as temperature T → 0, and at higher T usually an umklapp process (off electrons or phonons) is sufficient to relax the electronic momentum. Nevertheless, experiments have increasingly discovered evidence for this hydrodynamic flow regime in clean samples of graphene, GaAs, and other compounds, in recent years [2,3,4,5,6,7,8,9]; see [10] for a review.…”

Section: Introductionmentioning

confidence: 99%

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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Viscous electron flow in mesoscopic two-dimensional electron gas

Cited by 109 publications

References 21 publications

Stable branched electron flow

Stable branched electron flow

Hydrodynamic and ballistic AC transport in two-dimensional Fermi liquids

Sign of viscous magnetoresistance in electron fluids

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