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Disorder induced quantum phase transition in random-exchange spin-1/2 chains
K Hamacher1, J Stolze, W Wenzel
1Forschungszentrum Karlsruhe, Institut für Nanotechnologie, 76021 Karlsruhe, Germany.
Physical Review Letters
|September 13, 2002
Summary
Quenched bond disorder in spin-1/2 (XXZ) chains drives quantum phase transitions. This study reveals nonuniversal behavior and a disordered phase, challenging existing renormalization group predictions for quantum fluctuations and disorder interactions.
Area of Science:
- Condensed Matter Physics
- Quantum Magnetism
Background:
- Disorder is crucial for understanding quantum phase transitions.
- The spin-1/2 anisotropic Heisenberg (XXZ) chain is a key model for studying quantum magnetism.
Purpose of the Study:
- Investigate the impact of quenched bond disorder on the spin-1/2 XXZ chain.
- Explore disorder-induced quantum phase transitions and their characteristics.
- Compare findings with predictions from real-space renormalization group theories.
Main Methods:
- Theoretical investigation of the spin-1/2 XXZ chain model.
- Analysis of quenched bond disorder effects.
- Examination of average correlation functions and phase behavior.
Main Results:
- Observed nonuniversal behavior in average correlation functions for weak disorder.
- Identified a quantum phase transition into a strongly disordered phase.
- Found short-range correlations in the xy plane within the disordered phase.
- No evidence supporting the universal strong-disorder fixed point predicted by real-space renormalization group.
Conclusions:
- Disorder in XXZ chains leads to complex quantum phase transitions.
- The observed behavior deviates from standard renormalization group predictions.
- Suggests a novel relationship between quantum fluctuations and disorder in magnetic systems.