arXiv subjects

Raymond L. Orbach

Publications and source records attributed to Raymond L. Orbach.

4 recordsLinked to original sources

arXiv2026

Dynamics of spin glasses in two dimensions

Spin glass dynamics is a strong function of spatial dimensionality $D$. The lower critical dimension is close to 2.5, so that, in two dimensions, the condensation temperature $T_\text{g}=0$, and only fluctuations are present at finite temperatures. However, by using thin film multilayers, one can explore the dynamics in both $D=3$ and $D=2$ dimensions. Spin glass thin film multilayers transition from $D=3$ dynamics at short to intermediate times to $D = 2$ dynamics at long times. Correlation lengths of CuMn 4.5 nm multilayers at long times are shown to be grow more rapidly in $D=2$ as compared to $D=3$, and for the longest measurement time, experimentally reach equilibrium in qualitative agreement with simulations.

cond-mat.dis-nn↗

arXiv2025

Nature of temperature chaos in spin glasses

Temperature chaos (TC) in spin glasses has been claimed to exist no matter how small the temperature change, $ΔT$. However, experimental studies have exhibited a finite value of $ΔT$ for a transition to TC. This paper explores the onset of TC with much higher resolution than before and over a larger temperature range. We find that TC is always present, though small at the smallest $ΔT$ that we can reliably measure. However, it grows rapidly as $ΔT$ increases, the region of rapid growth coinciding with the $ΔT$ predicted from renormalization group arguments and observed experimentally. We are able to transcend the full range of TC, from the completely reversible state to one that is maximally decorrelated from the initially prepared state.

cond-mat.dis-nn↗

arXiv2021

Evidence for Temperature Chaos in Spin Glasses

We study the field cooled magnetization of a CuMn spin glass 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 $\ell_\mathrm{c}$, becoming comparable to the correlation length, $ξ$, at the crossover boundary. The extracted chaos exponent, $ζ= 1.1$, is in agreement with theoretical predictions. Our results strongly suggest temperature chaos exists in real spin glasses system.

cond-mat.dis-nn↗

arXiv2017

Magnetic Field Dependence of Spin Glass Free Energy Barriers

We measure the field dependence of spin glass free energy barriers in a thin amorphous Ge:Mn film through the time dependence of the magnetization. After the correlation length $ξ(t, T)$ has reached the film thickness $\mathcal {L}=155$~Å~so that the dynamics are activated, we change the initial magnetic field by $δH$. In agreement with the scaling behavior exhibited in a companion Letter [Janus collaboration: M. Baity-Jesi {\it et al.}, Phys. Rev. Lett. {\bf 118}, 157202 (2017)], we find the activation energy is increased when $δH < 0$. The change is proportional to $(δH)^2$ with the addition of a small $(δH)^4$ term. The magnitude of the change of the spin glass free energy barriers is in near quantitative agreement with the prediction of a barrier model.

cond-mat.dis-nn↗