researchers from the university of extremadura (spain) used the janus ii supercomputer to refine their calculation of the microscopic correlation length of and reproduce the experimental protocol to calculate macroscopic length of equilibrium dynamics in spin glasses, according to a report published on phys.org.

the janus ii supercomputer was used to determine coherence length in spin glasses.
(wikimedia commons)

the janus ii is located in the institute for biocomputation and physics of complex systems in zaragoza, spain and is based on reconfigurable fpga processors that allowed researchers to simulate one second of the experiment within the range of the experimental times, according to the report.

the article continued, “the researchers have reproduced a landmark experiment on the janus i and janus ii supercomputers that measures the coherence length in spin glasses. the coherence (correlation) length value estimated through analysis of microscopic correlation functions is quantitatively consistent with its measurements via macroscopic response functions.”

spin glasses are disordered magnets in which the magnetic spin of the component atoms is not aligned in a regular pattern.

systems such as spin glasses, polymers, supercooled liquids, and colloids take a long time to reach equilibrium, so slow at low temperatures that it is never attained at macroscopic levels. the researchers measure the dynamic through correlation length to show that particles at shorter distances are highly correlated.

one of the researchers noted, “this study provides a theoretical basis for studies in these physical systems, and the results obtained allow us to directly connect theoretical developments to the experimental ones. we took spin glasses as a reference, because they are cleaner to study as a reference system.”

the research was recently published in physical review letters. the report’s abstract stated:

“we first reproduce on the janus and janus ii computers a milestone experiment that measures the spin-glass coherence length through the lowering of free-energy barriers induced by the zeeman effect.

“secondly, we determine the scaling behavior that allows a quantitative analysis of a new experiment reported in the companion letter [s. guchhait and r. orbach, phys. rev. lett. 118, 157203 (2017)]. the value of the coherence length estimated through the analysis of microscopic correlation functions turns out to be quantitatively consistent with its measurement through macroscopic response functions.

“further, nonlinear susceptibilities, recently measured in glass-forming liquids, scale as powers of the same microscopic length.”