Spin Glass Correlation Length: a Caliper for Temperature Chaos

The spin glass correlation length is used as a caliper for the onset of temperature chaos in a Cu$_{0.94}$Mn$_{0.06}$ single crystal sample. From the values of the correlation length at different temperatures, we are able to calibrate the onset of the transition from reversible to chaotic behavior. We find that temperature chaos sets in abruptly as the chaos length scale $L^*$ becomes comparable to the spin glass correlation length $\xi$. We find the chaotic exponent for temperature chaos, $\zeta$, to be the order of unity assuming either fractal or compact glassy domains, in good agreement with previous theoretical analyses and numerical simulations

Opposite Influence of Perceptual Memory on Initial and Prolonged Perception of Sensory Ambiguity

Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretations

Evidence for temperature chaos in spin glasses

We study the field cooled magnetization of a CuMn spin glass (SG) under temperature perturbations. The T-cycling curves are compared with the reference curve without temperature cycling. There is a crossover from the cumulative aging region to noncumulative aging region as the temperature change is increased. The cumulative aging range scales with the chaos length, l(c), becoming comparable to the correlation length, xi, at the crossover boundary. The extracted chaos exponent, zeta = 1.1, is in agreement with theoretical predictions. Our results strongly suggest temperature chaos exists in real SG systems.This article is published as Zhai, Qiang, Raymond L. Orbach, and Deborah L. Schlagel. "Evidence for temperature chaos in spin glasses." Physical Review B 105, no. 1 (2022): 014434. DOI: 10.1103/PhysRevB.105.014434. Copyright 2022 American Physical Society. Posted with permission. DOE Contract Number(s): SC0013599

Workshop on Advanced Computational Materials Science: Application to Fusion and Generation IV Fission Reactors

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