We examine the spin-S quantum Heisenberg magnet with Gaussian-random, infinite-range exchange interactions. The quantum-disordered phase is accessed by generalizing to SU(M) symmetry and studying the large M limit. For large S the ground state is a spin glass, while quantum fluctuations produce a spin-fluid state for small S. The spin-fluid phase is found to be generically gapless-the average, zero temperature, local dynamic spin susceptibility obeys χ̄(ω)~ln(1/||ω||)+i(π/2)sgn(ω) at low frequencies.
Physical Review Letters
- Pub Date:
- May 1993
- Quantized spin models;
- Quantum statistical mechanics;
- Condensed Matter
- 13 pages, REVTEX, 2 figures available by request from email@example.com