Level statistics of XXZ spin chains with a random magnetic field
Abstract
The level-spacing distribution of a spin-1/2 XXZ chain is numerically studied under random magnetic field. We show explicitly how the level statistics depends on the lattice size L, the anisotropy parameter Δ, and the mean amplitude of the random magnetic field h. In the energy spectrum, quantum integrability competes with nonintegrability derived from the randomness, where the XXZ interaction is modified by the parameter Δ. When Δ≠0, the level-spacing distribution mostly shows Wigner-like behavior, while when Δ=0, Poisson-like behavior appears although the system is nonintegrable due to randomness. Poisson-like behavior also appears for Δ≠0 in the large h limit. Furthermore, the level-spacing distribution depends on the lattice size L, particularly when the random field is weak.
- Publication:
-
Physical Review B
- Pub Date:
- April 2004
- DOI:
- 10.1103/PhysRevB.69.132404
- arXiv:
- arXiv:cond-mat/0310752
- Bibcode:
- 2004PhRvB..69m2404K
- Keywords:
-
- 75.10.Pq;
- 75.10.Jm;
- 05.30.-d;
- 75.10.Nr;
- Spin chain models;
- Quantized spin models;
- Quantum statistical mechanics;
- Spin-glass and other random models;
- Condensed Matter - Statistical Mechanics
- E-Print:
- 4 pages, 3 figures, to be published in Phys. Rev. B