Friction emerges from energy dissipation at the contact interface between two materials in relative motion, and several reports estimate that friction contributes up to 23% of the world’s energy consumption [1, 2]. Structural superlubricity [3, 4] is a special regime of nanoscale motion in which two crystals are in incommensurate contact such that relative in-plane translation is associated with vanishing energy barrier crossing. These frictionless special states have been so far realized in multilayered graphene and other van der Waals contacts with hexagonal or triangular crystalline symmetries leading to isotropic frictionless contacts for a wide range of twist angles. Recently, a new class of structural superlubricity has been predicted with a flat directional translational potential energy landscape, enabling nanohighways [5], has however not yet been demonstrated. In this talk, I will show recent low energy electron microscopy (LEEM) results which allow for visualization of the growth of α-bismuthene (α-Bi) islands on highly ordered pyrolithic graphite (HOPG). The spontaneous back-and-forth diffusion over hundreds of nanometers of massive islands (up to 20000 nm²) is a manifestation of directional superlubricity, supported by registry index simulations. Finally, I will show that the α-Bi islands’ motion dynamics follows Lévy flight statistics [7], which have been to date very elusive in solid state systems.

[1] K. Holmberg and A. Erdermir, Friction 5, 263 (2017) [2] J. Luo et al., Nano Energy 86, 106092 (2021) [3] O. Hod et al., Phys. Rev. B 86, 075444 (2012) [4] O. Hod et al, Nature 563, 485 (2018) [5] E. Panizon et al., Nanoscale 15, 1299 (2023) [6] M. Le Ster et al., submitted. [7] W. D. Luedtke and U. Landman, Phys. Rev. Lett. 82, 19 (1999)