RT Journal Article T1 Superposition principle and nonlinear response in spin glasses A1 Paga, I. A1 Zhai, Q. A1 Baity-Jesi, M. A1 Calore, E. A1 Cruz, A. A1 Cummings, C. A1 Fernández Pérez, Luis Antonio A1 Gil-Narvion, J. M. A1 González-Adalid Pemartín, Isidoro A1 Gordillo-Guerrero, A. A1 Iñiguez, D. A1 Kenning, G. G. A1 Maiorano, A. A1 Marinari, E. A1 Martín Mayor, Víctor A1 Moreno-Gordo, J. A1 Muñoz Sudupe, Antonio A1 Navarro, D. A1 Orbach, R. L. A1 Parisi, G. A1 Perez-Gaviro, S. A1 Ricci-Tersenghi, F. A1 Ruiz-Lorenzo, J. J. A1 Schifano, S. F. A1 Schlagel, D. L. A1 Seoane Bartolomé, Beatriz A1 Tarancon, A. A1 Yllanes, D. AB The extended principle of superposition has been a touchstone of spin-glass dynamics for almost 30 years. The Uppsala group has demonstrated its validity for the metallic spin glass, CuMn, for magnetic fields H up to 10 Oe at the reduced temperature T-r = T/T-g = 0.95, where T-g is the spin-glass condensation temperature. For H > 10 Oe, they observe a departure from linear response which they ascribe to the development of nonlinear dynamics. The thrust of this paper is to develop a microscopic origin for this behavior by focusing on the time development of the spin-glass correlation length, xi (t, t(w); H). Here, t is the time after H changes, and t(w) is the time from the quench for T > T-g to the working temperature T until H changes. We connect the growth of xi (t, t(w); H) to the barrier heights Lambda(t(w)) that set the dynamics. The effect of H on the magnitude of Delta (t(w)) is responsible for affecting differently the two dynamical protocols associated with turning H off (TRM, or thermoremanent magnetization) or on (ZFC, or zero-field-cooled magnetization). This difference is a consequence of nonlinearity based on the effect of H on Delta (t(w)). Superposition is preserved if Delta(t(w)) is linear in the Hamming distance Hd (proportional to the difference between the self-overlap qEA and the overlap q[ Delta(t(w))]). However, superposition is violated if Delta(t(w)) increases faster than linear in Hd. We have previously shown, through experiment and simulation, that the barriers Delta (t(w)) do increase more rapidly than linearly with Hd through the observation that the growth of. (t, t(w); H) slows down as. (t, t(w); H) increases. In this paper, we display the difference between the zero-fieldcooled.ZFC(t, t(w); H) and the thermoremanent magnetization.TRM(t, t(w); H) correlation lengths as H increases, both experimentally and through numerical simulations, corresponding to the violation of the extended principle of superposition in line with the finding of the Uppsala Group. PB American Physical Society SN 2469-9950 YR 2023 FD 2023-06-23 LK https://hdl.handle.net/20.500.14352/125901 UL https://hdl.handle.net/20.500.14352/125901 LA eng NO Paga, I., et al. «Superposition Principle and Nonlinear Response in Spin Glasses». Physical Review B, vol. 107, n.o 21, junio de 2023, p. 214436. DOI.org (Crossref), https://doi.org/10.1103/PhysRevB.107.214436 NO ©2023 American Physical Society.These authors contributed equally to this work.DE-SC0013599;DE-AC02-07CH11358;GR21014;IB20079;Grant nº 454949; 2021-2023 Margarita Salas grant;FPU 18/02665 NO Department of Energy (US) NO University of Iowa (US) NO Ministerio de Ciencia, Innovación y Universidades (España) NO Agencia Estatal de Investigación (España) NO European Commission NO Junta de Extremadura NO Simons Foundation NO Chan Zuckerberg Biohub NO Universitá la Sapienza (Italia) DS Docta Complutense RD 31 dic 2025