Open Conference Systems, StatPhys 27 Main Conference

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The dimensional crossover in spin-glasses: from bulk systems to thin films
Ilaria Paga

##manager.scheduler.building##: Edificio Santa Maria
##manager.scheduler.room##: Auditorio San Agustin
Date: 2019-07-08 11:45 AM – 03:30 PM
Last modified: 2019-06-15

Abstract


In the last five years, a new experimental protocol, introduced by the Austin group has challenged theorists. Indeed, by studying the time growth of spin-glass correlation length on multilayer samples of thin film, the lower critical dimension has been measured experimentally [S. Guchhait and R. L. Orbach Phys. Rev. Lett. 112, (2014) 126401] and precision measurements of the aging rate has been obtained [Q. Zhai et al. Phys. Rev. B 95 (2017) 054304, S. Guchhait and R. L. Orbach Phys. Rev. Lett. 118,(2017) 157203].

 

The above experimental success clearly shows that playing with the sample geometry is a powerful tool. This tool has been mostly disregarded by theorists, up to now. Here I shall report on an extensive numerical investigation of the aging dynamics of a spin-glass on samples with a film geometry [L.A. Fernandez, E. Marinari, V. Martin-Mayor, I. Paga and J.J. Ruiz-Lorenzo in preparation (2019)].

 

Our study focuses on the same quantity considered in experiments, namely the time-growing spin glass correlation length. The main hypothesis behind the experimental analysis (never verified before in a thorough theoretical study) is the existence of a dimensional crossover when the correlation length reaches the film width, followed by a dynamical arrest.

 

We have simulated the spin glass dynamics in films of varying width in all the relevant dynamic regimes (from picoseconds to thermal equilibrium, which in films is reachable), for several temperatures. Scale-invariance greatly simplifies the problem. The film width is a relevant length scale: for short times, while the correlation length is shorter than the thickness, the dynamics follows the bulk-system’s behavior. However, when the bulk correlation length approaches the film width, a crossover to two-dimensional dynamics takes place. This crossover is described in terms of scaling functions. Although the picture used by experimentalists of a complete dynamical arrest is clearly an oversimplification, the basic hypothesis in their analysis is confirmed.

Funding: We acknowledge support from the European Research Council, under the European Union’s Horizon 2020 research and innovation program (grant agreement No [694925]), and from MINECO (Spain), through contracts No. FIS2015-65078-C2, No. FIS2016-76359-P.