Valley-Controlled Viscosity of Two-Dimensional Dirac Fluids
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arXiv
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| Format: | Preprint |
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2026
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| _version_ | 1866911672181981184 |
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| author | Ermakov, Alexey Principi, Alessandro |
| author_facet | Ermakov, Alexey Principi, Alessandro |
| contents | Motivated by recent experiments in weakly hybridized small-angle twisted bilayer graphene, we investigate how valley imbalance affects the viscosity of two-dimensional Dirac fluids. We show that shifting the two low-energy Dirac cones relative to one another provides a direct knob to control the viscosity of the electron fluid. As the splitting is increased, the system passes through distinct transport regimes associated with valley depletion, charge-neutrality crossover, and the onset of electron-hole scattering, producing a pronounced nonmonotonic response. To place this result in context, we also analyze the viscosity in monolayer graphene (MLG) and two-dimensional electron gas (2DEG). We show that, due to the strong dependence of its inertial mass density on temperature, the kinematic viscosity of MLG is a monotonically decreasing function of temperature. Our results identify valley control as a route to tuning hydrodynamic transport in Dirac materials and clarify the interplay between band structure, scattering phase space, and screening in setting the viscous response. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_11069 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Valley-Controlled Viscosity of Two-Dimensional Dirac Fluids Ermakov, Alexey Principi, Alessandro Mesoscale and Nanoscale Physics Motivated by recent experiments in weakly hybridized small-angle twisted bilayer graphene, we investigate how valley imbalance affects the viscosity of two-dimensional Dirac fluids. We show that shifting the two low-energy Dirac cones relative to one another provides a direct knob to control the viscosity of the electron fluid. As the splitting is increased, the system passes through distinct transport regimes associated with valley depletion, charge-neutrality crossover, and the onset of electron-hole scattering, producing a pronounced nonmonotonic response. To place this result in context, we also analyze the viscosity in monolayer graphene (MLG) and two-dimensional electron gas (2DEG). We show that, due to the strong dependence of its inertial mass density on temperature, the kinematic viscosity of MLG is a monotonically decreasing function of temperature. Our results identify valley control as a route to tuning hydrodynamic transport in Dirac materials and clarify the interplay between band structure, scattering phase space, and screening in setting the viscous response. |
| title | Valley-Controlled Viscosity of Two-Dimensional Dirac Fluids |
| topic | Mesoscale and Nanoscale Physics |
| url | https://arxiv.org/abs/2605.11069 |