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Directional ordering of fluctuations in a two-dimensional compass model
Anup Mishra1, Michael Ma, Fu-Chun Zhang
1Department of Physics, University of Cincinnati, Cincinnati, Ohio 45221-0011, USA.
Physical Review Letters
|December 17, 2004
Summary
This study reveals directional orbital interactions in Mott insulators, leading to partial orbital ordering stabilized by entropy. The transition to a disordered phase follows Ising universality class behavior.
Area of Science:
- Condensed Matter Physics
- Materials Science
Background:
- Mott insulating phase in transition metal oxides features directional orbital-orbital interactions.
- These interactions are directional in both orbital and real space.
Purpose of the Study:
- To explore a classical two-dimensional model exhibiting directional orbital coupling.
- To investigate the emergence of orbital ordering and phase transitions in this model.
Main Methods:
- Exact mapping techniques.
- Multicanonical Monte Carlo simulations.
Main Results:
- The model demonstrates partial orbital ordering, specifically directional ordering of fluctuations, at low temperatures.
- This ordering is stabilized by an entropy gap, despite ground state degeneracy.
- The phase transition to a disordered state belongs to the Ising universality class.
Conclusions:
- Directional orbital interactions can lead to complex ordering phenomena in simplified models.
- The study provides insights into the fundamental physics of Mott insulating phases and phase transitions.
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