CPM Seminar

Superballistic conduction in antidot graphene superlattices

Mario Amado

Universidad de Salamanca

In most solids, electron transport is typically determined by sample geometry, electron-phonon interaction, and electron-impurity interaction, characterized by the inelastic mean free path (l_e). In such solids, electron-electron interactions, characterized by the elastic mean free path (l_ee), play a secondary role (l_ee >> l_e). However, the combination of recent progress in the production of ultra-high-quality two-dimensional-materials and their nanofabrication into non-standard geometrical devices where the carrier flow would be non-uniform have facilitated the exploration of electrical transport in the hydrodynamic regime [1,2]. There, increasing l_e makes elastic interactions more significant and in this regime Coulomb interactions drive the carrier motion from an independent-particle scenario towards a collective motion of a viscous "carrier fluid". In such regime, it has been found how at higher temperatures the overall resistance experienced by the carriers is diminished [3], opening an extraordinarily challenging path for the generation of low consumption electronics.

In this work [4], we will present the study of the hydrodynamic carrier flow in fully encapsulated monolayer graphene heterostructures where the devices have been shaped into antidot superlattices. We will show how above a certain temperature, graphene encapsulated in hBN can exhibit large l_e, greater than l_ee, making it an ideal candidate for the study of the hydrodynamic regime and how viscous carrier flow in graphene exhibits exotic signatures such as superballistic conduction. We will show the electrical response of the antidot superlattices as a function of temperature, carrier density and external magnetic field, finding for some of them scaling laws which help us discuss the different transport regimes. We will support our findings with detailed simulations of the Boltzmann transport equation and have found an enhanced superballistic effect with a non-monotonic behavior with the magnetic field. Our simulations provide the explanation for our experimental results contributing to a better under-standing of hydrodynamic transport and superballistic conduction which will help establishing the building blocks for a novel technological paradigm.

References
[1] M. Polini and A. K. Geim, Physics Today 73 (2020) 28.
[2] G. Varnavides, A. Yacoby, C. Felser, and P.Narang, Nature Review Materials 8 (2023) 726.
[3] A. C. Keser, D. Q. Wang, O. Klochan, D. Y. H. Ho, O. A. Tkachenko, V. A. Tkachenko, D. Culcer, S. Adam, I. Farrer, D. A. Ritchie, O- P. Sushkov, A. R. Hamilton. Physical Review X 11 (2021) 031030.
[4] J. Estrada-Álvarez et al Physical Review X 15, 011039 (2025).