ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarMaxime Le SterUniversity of Lodz (host: Palotás 
Krisztián)Directional Structural Superlubricity in α-Bi on graphiteTuesday, 7 
May 2024, 10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference RoomFriction 
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) Minden érdeklődőt szívesen látunk! - Everyone is welcome to 
attend.Attila Nagysem-admin AT szfki.hu