Non-compact local excitations in spin glasses

Julien Lamarcq 1, Jean-Philippe Bouchaud 1, Olivier C. Martin 2, Marc Mézard 2

Europhysics Letters (EPL) 58 (2002) 321

We study numerically the local low-energy excitations in the 3-d Edwards-Anderson model for spin glasses. Given the ground state, we determine the lowest-lying connected cluster of flipped spins with a fixed volume containing one given spin. These excitations are not compact, having a fractal dimension close to two, suggesting an analogy with lattice animals. Also, their energy does not grow with their size; the associated exponent is slightly negative whereas the one for compact clusters is positive. These findings call for a modification of the basic hypotheses underlying the droplet model.

  • 1. Service de physique de l'état condensé (SPEC),
    CNRS : URA2464 – CEA : DSM/IRAMIS
  • 2. Laboratoire de Physique Théorique et Modèles Statistiques (LPTMS),
    CNRS : UMR8626 – Université Paris XI - Paris Sud