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Quantum Criticality in Quasi-Two-Dimensional Itinerant Antiferromagnets.
1Department of Physics and Astronomy, University of California, Riverside, California 92521, USA.
Physical Review Letters
|November 14, 2015
Summary
This study reveals that quantum-critical itinerant fermions in antiferromagnetic systems can be modeled using a dissipative quantum XY model. Topological excitations, not spin fluctuations, govern critical behavior, explaining observed resistivity and entropy anomalies.
Area of Science:
- Condensed Matter Physics
- Quantum Magnetism
Background:
- Quasi-two-dimensional itinerant fermions near antiferromagnetic (AFM) quantum criticality exhibit unique properties like linear temperature resistivity.
- These properties are observed in materials such as Fe-based superconductors and heavy-fermion compounds.
Purpose of the Study:
- To develop a generic model for itinerant antiferromagnets.
- To connect the critical fluctuations of these systems to a dissipative quantum XY model.
Main Methods:
- Canonical transformation of an itinerant antiferromagnet model.
- Analysis of critical fluctuations in the long-wavelength limit.
- Evaluation of fluctuations in a 2D dissipative quantum XY model.
Main Results:
- Critical fluctuations are dominated by topological excitations, not renormalized spin fluctuations, in a significant parameter regime.
- Fluctuations exhibit separable spatial and temporal dependence with an effective dynamic exponent z=∞.
- Observed linear resistivity and TlnT specific heat contributions are explained by the model.
Conclusions:
- The dissipative quantum XY model provides a unified framework for understanding quantum criticality in itinerant antiferromagnets.
- Topological excitations play a crucial role in the emergent properties of these systems.
- The theory offers testable predictions for future experimental verification.
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