Frustrating disorder for continuous spins: low-temperature properties of spin glasses and random-field systems

• Applicant: Professor Dr. Martin Weigel
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: from 2007 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 55457478

Spin glasses and random-field systems are models of disordered media with often highly counter-intuitive properties and an enormous number of experimental realisations in condensed matter physics, including highly frustrated magnets, superfluid helium, amorphous solids and ferroelectric materials. Novel phases of matter such as spin glasses, spin liquids and spin ices likely lie at the heart of several technologically important phenomena, such as high temperature superconductivity, colossal magnetoresistance, and the anomalous Hall effect. Besides, models of such systems have applications in seemingly rather distant fields such as the theory of associative memory, models of the immune system or error correcting codes. These applications and the theoreticians’ interest in a novel and unconventional state of matter have prompted a large and ongoing research effort towards an understanding of the phenomena involved. Despite an early spectacular success in formulating and solving a mean-field theory revealing an astonishingly complex structure of the spin-glass phase, it was found a tricky and so-far elusive goal to ultimately decide about the relevance of these mean-field results for the real two- and three-dimensional systems realised experimentally. Due to its relative simplicity, most research has focused on the discrete Ising model of extreme spin-anisotropy, leading to some understanding of its low-temperature properties. The proposed research aims at relaxing this simplification, investigating in detail spin glasses and random-field systems with continuous spins, which are often much more realistic for the experimentally realised systems.

• DFG Programme: Independent Junior Research Groups
• International Connection: United Kingdom