Theoretical determination of hydrodynamic window in monolayer and bilayer graphene from scattering rates

Ho, Derek Y. H.; Yudhistira, Indra; Chakraborty, Nilotpal; Adam, Shaffique

doi:10.1103/physrevb.97.121404

Cited by 67 publications

(68 citation statements)

References 31 publications

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“…Clearly, at T 10 K, τ deviates visibly from τ p , with τ e−e being the relevant cut-off, while τ e−ph is not important. This resembles the recently found observation window for hydrodynamic effects in graphene [54].…”

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confidence: 90%

Commensurability Oscillations in One-Dimensional Graphene Superlattices

et al. 2018

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We report the experimental observation of commensurability oscillations (COs) in 1D graphene superlattices. The widely tunable periodic potential modulation in hBN-encapsulated graphene is generated via the interplay of nanopatterned few-layer graphene acting as a local bottom gate and a global Si back gate. The longitudinal magnetoresistance shows pronounced COs when the sample is tuned into the unipolar transport regime. We observe up to six CO minima, providing evidence for a long mean free path despite the potential modulation. Comparison to existing theories shows that small-angle scattering is dominant in hBN/graphene/hBN heterostructures. We observe robust COs persisting to temperatures exceeding T=150 K. At high temperatures, we find deviations from the predicted T dependence, which we ascribe to electron-electron scattering.

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confidence: 90%

Commensurability Oscillations in One-Dimensional Graphene Superlattices

et al. 2018

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“…The standard dependence l ee = ℏ v F ε F /( k B T ) 2 translates into the scaling l ee ∼ n 3/2 , which is much faster than the n 1/2 dependence in MLG. This allowed us to explore a wider range of l ee than in MLG by varying the carrier density for a given T (see below), providing a convenient knob to tune the Kn value and probe the quasiballistic-to-hydrodynamic transition 29 .…”

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confidence: 99%

Fluidity onset in graphene

et al. 2018

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Viscous electron fluids have emerged recently as a new paradigm of strongly-correlated electron transport in solids. Here we report on a direct observation of the transition to this long-sought-for state of matter in a high-mobility electron system in graphene. Unexpectedly, the electron flow is found to be interaction-dominated but non-hydrodynamic (quasiballistic) in a wide temperature range, showing signatures of viscous flows only at relatively high temperatures. The transition between the two regimes is characterized by a sharp maximum of negative resistance, probed in proximity to the current injector. The resistance decreases as the system goes deeper into the hydrodynamic regime. In a perfect darkness-before-daybreak manner, the interaction-dominated negative response is strongest at the transition to the quasiballistic regime. Our work provides the first demonstration of how the viscous fluid behavior emerges in an interacting electron system.

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“…Finally, in our analysis we considered other possible relevant mechanisms for transport in tBG and found them to be negligible. For example, Umklapp scattering [32] is irrelevant for the densities we consider because only a small area of the moiré Brillouin zone is occupied and the hydrodynamic electron-hole scattering [33] contribution to resistivity remains weaker than impurity scattering for T < 100 K. We conclude that for the experimentally relevant temperatures and densities the resistivity is determined only by the interplay between charged impurities and gauge phonons.…”

Section: Mechanismmentioning

confidence: 99%

Gauge-phonon dominated resistivity in twisted bilayer graphene near magic angle

et al. 2019

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Recent experiments on twisted bilayer graphene (tBG) close to magic angle show that a small relative rotation in a van der Waals heterostructure greatly alters its electronic properties. We consider various scattering mechanisms and show that the carrier transport in tBG is dominated by a combination of charged impurities and acoustic gauge phonons. Charged impurities still dominate at low temperature and densities because of the inability of Dirac fermions to screen long-range Coulomb potentials at charge neutrality; however, the gauge phonons dominate for most of the experimental regime because although they couple to current, they do not induce charge and are therefore unscreened by the large density of states close to magic angle. We show that the resistivity has a strong monotonically decreasing carrier density dependence at low temperature due to charged impurity scattering, and weak density dependence at high temperature due to gauge phonons. Away from charge neutrality, the resistivity increases with temperature, while it does the opposite close to the Dirac point. A non-monotonic temperature dependence observed only at low temperature and carrier density is a signature of our theory that can be tested in experimentally available samples. * These two authors contributed equally to this work †

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Theoretical determination of hydrodynamic window in monolayer and bilayer graphene from scattering rates

Cited by 67 publications

References 31 publications

Commensurability Oscillations in One-Dimensional Graphene Superlattices

Commensurability Oscillations in One-Dimensional Graphene Superlattices

Fluidity onset in graphene

Gauge-phonon dominated resistivity in twisted bilayer graphene near magic angle

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