Neel-dimer transition in an antiferromagnetic Heisenberg model and deconfinement of spinons at the critical point

Journal Article · Mon Nov 01 04:00:00 EST 2004 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.70.174407· OSTI ID:20664945

Yoshioka, Daisuke; Arakawa, Gaku; Ichinose, Ikuo; Matsui, Tetsuo ^[1]

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1. Department of Applied Physics, Graduate School of Engineering, Nagoya Institute of Technology, Nagoya, 466-8555 (Japan)

Quantum phase transition from the Neel to the dimer states in an antiferromagnetic (AF) Heisenberg model on square lattice is studied. We introduce a control parameter {alpha} for the exchange coupling that connects the Neel ({alpha}=0) and the dimer ({alpha}=1) states. We employ the CP{sup 1} representation of the s=(1/2) spin operator and integrate out the half of the CP{sup 1} variables at odd sites to obtain a CP{sup 1} nonlinear {sigma} model. The effective coupling constant is a function of {alpha}, and at {alpha}=0, the CP{sup 1} model is in the ordered phase that corresponds to the Neel state of the AF Heisenberg model. A phase transition to the dimer state occurs at a certain critical value of {alpha}{sub C} as {alpha} increases. In the Neel state, the dynamical composite U(1) gauge field in the CP{sup 1} model is in a Higgs phase, and low-energy excitations are gapless spin waves. In the dimer phase, a confinement phase of the gauge theory with s=1 excitations is realized. For the critical point, we argue that a deconfinement phase, which is similar to the Coulomb phase in three spatial dimensions, is realized and s=(1/2) spinons appear as low-energy excitations.

• OSTI ID: 20664945
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 17 Vol. 70; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANTIFERROMAGNETISM
CONFINEMENT
COUPLING
COUPLING CONSTANTS
DIMERS
ELECTRONS
EXCHANGE INTERACTIONS
EXCITATION
GAUGE INVARIANCE
HEISENBERG MODEL
HIGGS MODEL
PHASE TRANSFORMATIONS
QUANTUM FIELD THEORY
SPIN WAVES