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MA: Fachverband Magnetismus
MA 14: Focus Session: Frustrated Magnetism and Local Order (joint session MA/TT)
MA 14.7: Talk
Tuesday, March 19, 2024, 12:15–12:30, H 1058
Noncoplanar and chiral spin states on the way towards Néel ordering in fullerenes — •Attila Szabó1, Sylvain Capponi2, and Fabien Alet2 — 1Max-Planck-Institut für Physik komplexer Systeme, Dresden, Germany — 2Laboratoire de Physique Théorique, Toulouse, France
Magnetic ordering can be detected in finite lattices through the emergence of Bragg peaks in ground-state structure factor or through the spectrum of low-energy excited states, which form an Anderson tower of states generated by Goldstone modes of the incipient symmetry breaking. In this talk, I will generalise these methods to large fullerenes, where incipient Néel ordering on the network of hexagonal faces is frustrated by a low density of pentagons. Using high-accuracy variational Monte Carlo based on group-convolutional neural networks, we obtain the symmetry-resolved low-energy spectrum of the spin-1/2 Heisenberg model on several highly symmetric fullerene geometries, including the famous C60 buckminsterfullerene. We show that their correlation functions contain high-intensity Bragg peaks consistent with Néel-like ordering, while the low-energy spectrum is organised into a tower of states. Competition with frustration, however, turns the simple Néel order into a noncoplanar one. Remarkably, we find and predict chiral incipient ordering in a large number of fullerene structures. Our findings may have interesting ramifications for the nature of superconductivity in metal fullerides.
Keywords: Noncoplanar magnetic order; Fullerenes; Anderson tower of states; Neural quantum states; Machine learning