Hydrodynamic electron flow in antidot graphene superlattices

In most materials, electrons behave like a gas, moving independently and scattering inelastically off impurities and phonons, causing energy losses in the form of electrical resistance. This resistance is minimized in the ballistic regime at low temperatures, where inelastic scattering is reduced. However, in ultra-high-quality materials, the reduction of impurities allows electrons to interact with each other and flow collectively like a liquid. In this "hydrodynamic" regime, electrons can avoid obstacles in their path rather than scattering off them [1], like water flows around obstacles in a river [Fig 1.a)]. This regime has attracted significant interest, not only for offering a new way to study fluid dynamics but also because electrical resistance can drop below the ballistic limit in conventional systems, a phenomenon known as super ballistic conduction. In this context, graphene/hBN systems are ideal for studying the hydrodynamic regime, not only due to their minimal impurity levels but also because graphene is minimally affected by phonons, allowing hydrodynamic effects even at near room temperature. Additionally, to induce these effects, it is necessary to design specific geometries that curve the electron trajectories, much like how obstacles in a river generate turbulence in water. In this work [2,3], we have designed and fabricated a novel antidot superlattice in graphene/hBN heterostructures [Fig 1.b)]. The measurements revealed an enhanced superballistic effect, with a clear drop in resistance below the ballistic limit [Fig 1.c)]. Furthermore, for the first time, we observed that super ballistic conduction exhibited non-monotonic behaviour as a function of the magnetic field, allowing for in situ modulation of the collective behaviour of electrons using both temperature and magnetic field. This research could open new avenues in electronics and nanotechnology by enabling devices that could operate more efficiently, consume less power, and generate less heat—key improvements for advancing computers and other electronic technologies.

[1] R. Krishna Kumar et ak, . "Superballistic flow of viscous electron fluid through graphene constrictions" Nature Physics 13, 1182–1185 (2017).
[2] J. Estrada-Álvarez*, J. Salvador-Sánchez* et al. "Superballistic conduction in hydrodynamic antidot graphene superlattices" Phys. Rev. X, 15, 011039 (2025).
[3] Mark Buchanan. "Holey Material Enhacnes Electron Flow" Physics Focus 18, 4 (2025).