We consider random quantum (tight-binding, XX, and Ising) spin chains in the off-critical region and study their Griffiths-McCoy singularities. These are obtained from the density of states of the low-energy excitations, which is exactly calculated by the Dyson-Schmidt method. In large finite systems, the low-energy excitations are shown to follow the statistics of extremes and their distribution is given by the Fréchet form. The relation between the Dyson-Schmidt technique and the strong disorder renormalization group method is also discussed.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Apr 8 2008|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics