Magnetic-field symmetry breaking in spin glasses

ORAL

Abstract

Time-reversal symmetry is spontaneously broken in spin glasses below their glass temperature. Under such conditions, the standard assumption about the equivalence of the most standard protocols (i.e. no big difference between switching the field on or off, as it is sometimes said) is not really justified. In fact, we show here that the spin-glass coherence length behaves differently in the zero-field-cooled (ZFC, magnetic field is turned on) and thermoremanent-magnetization (TRM, magnetic field is turned off) protocols. This conclusion is reached through experiments, carried out on two CuMn single-crystal samples, and through massive simulations on the Janus~II dedicated supercomputer. In agreement with the predictions of a simple dynamical model that assumes that the ultrametric tree of states survives the switching-on of the magnetic field, we conclude that (all parameters being kept equal) the spin-glass coherence length is larger in the ZFC protocol. This has implications for the extended principle of superposition, which, while holding at H = 0, breaks down for finite magnetic fields. Preliminary simulation results support this observation.

*This work was supported in part by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division, under Award N. DESC0013599, and performed at the Ames Laboratory, which is operated for the U.S. DOE by Iowa State University under contract N. DE-AC02-07CH11358. We were partly funded by MINECO, AEI (Spain), and FEDER (EU) through Grants N. PID2020-112936GB-I00, N. PID2019-103939RB-I00, N. PGC2018-094684-B-C21 and PGC2018-094684-B-C22, by the Junta de Extremadura (Spain) and Fondo Europeo de Desarrollo Regional (FEDER, EU) through Grant N. GR21014 and N. IB20079 and by the DGA-FSE. This project has also received funding from the ERC under the European Union's Horizon 2020 research and innovation program (Grant N. 694925-LotglasSy). DY was supported by the Chan Zuckerberg Biohub,IGAP was supported by MCIU (Spain) through FPU grant N. FPU18/02665. BS was supported by the Comunidad de Madrid and the UCM (Spain) through the Atracci'on de Talento program (Ref. 2019-T1/TIC-12776). JMG was supported by the Ministerio de Universidades and the EU/PRTR through 2021-2023 Margarita Salas grant.

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Publication: https://arxiv.org/pdf/2207.10640.pdf

Presenters

  • Ilaria Paga

    • CNR-Nanotec Rome
    • CNR-Nanotec, Rome

Authors

  • Ilaria Paga

    • CNR-Nanotec Rome
    • CNR-Nanotec, Rome