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

Article

关键词: DIMENSIONAL QUANTUM ANTIFERROMAGNETS;    T-J MODEL;    GROUND-STATES;    QUARK CONFINEMENT;    HIGH-TEMPERATURE;    GAUGE-THEORIES;    VALENCE-BOND;    SUPERCONDUCTIVITY;    INSTANTONS;    PEIERLS;   

DOI  :  10.1103/PhysRevB.70.174407

来源: SCIE

【 摘 要 】

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 a for the exchange coupling that connects the Neel (alpha=0) and the dimer (alpha=1) states. We employ the CP1 representation of the s=1/2 spin operator and integrate out the half of the CP1 variables at odd sites to obtain a CP1 nonlinear sigma model. The effective coupling constant is a function of alpha, and at alpha = 0, the CP1 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(C) as alpha increases. In the Neel state, the dynamical composite U(1) gauge field in the CP1 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.

【 授权许可】

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