Triangular-lattice anisotropic dimerized Heisenberg antiferromagnet: Stability and excitations of the quantum paramagnetic phase

Author(s)

Doretto, R. L. ^[1] ; Vojta, Matthias ^[2]

Affiliation

^[1] Univ Estadual Paulista, Inst Fis Teor, BR-01140070 Sao Paulo - Brazil

^[2] Tech Univ Dresden, Inst Theoret Phys, D-01062 Dresden - Germany

• Document type: Journal article
• Source: Physical Review B; v. 85, n. 10, p. 104416, 2012.
• Web of Science Citations: 9

Abstract

Motivated by experiments on nonmagnetic triangular-lattice Mott insulators, we study one candidate paramagnetic phase, namely the columnar dimer (or valence-bond) phase. We apply variants of the bond-operator theory to a dimerized and spatially anisotropic spin-1/2 Heisenberg model and determine its zero-temperature phase diagram and the spectrum of elementary triplet excitations (triplons). Depending on model parameters, we find that the minimum of the triplon energy is located at either a commensurate or an incommensurate wave vector. Condensation of triplons at this commensurate-incommensurate transition defines a quantum Lifshitz point, with effective dimensional reduction that possibly leads to nontrivial paramagnetic (e.g., spin-liquid) states near the closing of the triplet gap. We also discuss the two-particle decay of high-energy triplons, and we comment on the relevance of our results for the organic Mott insulator (EtMeP)-P-3[Pd(dmit)(2)](2). (AU)

• FAPESP's process: 10/00479-6 - Two-dimensional magnetic systems
• Grantee: Ricardo Luis Doretto
• Support Opportunities: Research Grants - Young Investigators Grants