Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 59: Spins on Surfaces at the Atomic Scale I

O 59.6: Talk

Wednesday, March 19, 2025, 11:45–12:00, H6

Realization of separation of time scales in a heterogeneous atomic Boltzmann machine — •Kira Junghans, Hermann Osterhage, Werner M. J. van Weerdenburg, Niek M. M. Aarts, Anna M. H. Krieg, Tren Jacobs, Niels P. E. van Mullekom, Ruben Christianen, Eduardo J. Domínguez Vázquez, Hilbert J. Kappen, and Alexander A. Khajetoorians — Radboud University, Nijmegen, The Netherlands

The Boltzmann machine (BM) describes an energy-based neural network formed by coupled, fluctuating Ising spins [1]. A material realization of the Boltzmann machine was constructed using the complex stochastic dynamics of coupled Co atoms on the surface of black phosphorus (BP) [1]. Neurons and synapses were realized by a separation of time scales exploiting the anisotropic electronic structure of BP [1]. Using the anisotropy of the substrate is a limitation in scaling this concept.
Here, we study the coupled dynamics of different types of atoms on BP, which exhibit orbital memory [2,3]. We study the influence of the coupling on stochastic dynamics in heteroatomic dimer and trimer configurations with scanning tunneling microscopy (STM). Further, we discuss how the multi-well energy landscape can be influenced by an applied AC signal.
[1] B. Kiraly et al., Nat. Nanotechn. 16, 414 (2021).
[2] B. Kiraly et al., Nat. Comm. 9, 3904 (2018).
[3] B. Kiraly et al., Phys. Rev. Research 4, 033047 (2022).

Keywords: Orbital memory; Boltzmann machine; Scanning Tunneling Microscopy (STM)