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

Abstract

Motivated by experiments on non-magnetic triangular-lattice Mott insulators, we study one candidate paramagnetic phase, 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 wavevector. Condensation of triplons at this commensurate-incommensurate transition defines a quantum Lifshitz point, with effective dimensional reduction which possibly leads to non-trivial 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 EtMe3P[Pd(dmit)2]2.

14 pages, 12 figures, new figures added, final version

References in corpus (13)

• Bose-Einstein Condensation in Magnetic Insulators
• Quantum magnetism and criticality
• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
• Effective spin model for the spin-liquid phase of the Hubbard model on the triangular lattice
• Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator $\kappa$-(ET)${}_2$Cu${}_2$(CN)${}_3$
• Ordering in spatially anisotropic triangular antiferromagnets
• Global phase diagrams of frustrated quantum antiferromagnets in two dimensions: doubled Chern-Simons theory
• Evidence of Unconventional Universality Class in a Two-Dimensional Dimerized Quantum Heisenberg Model
• Mott Transition in a Valence Bond Solid Insulator with a Triangular Lattice
• Incommensurate correlations in the anisotropic triangular Heisenberg lattice
• Modified spin-wave theory with ordering vector optimization II: Spatially anisotropic triangular lattice and $J_1{J}_2{J}_3$ model with Heisenberg interactions
• Order in a Spatially Anisotropic Triangular Antiferromagnet
• Decay of quasiparticles in quantum spin liquids

Cited by in corpus (12)

• Plaquette valence-bond solid in the square lattice J1-J2 antiferromagnet Heisenberg model: a bond operator approach
• Quantum disorder in the spatially completely anisotropic triangular lattice II: frustrated hard-core bosons
• Quantum disorder in the spatially completely anisotropic triangular lattice I: Heisenberg $S=1/2$ antiferromagnet
• "Quasi-particle breakdown" in the quasi-one-dimensional Ising ferromagnet CoNb${}_2$O${}_6$
• Quantum Damping of Skyrmion Crystal Eigenmodes due to Spontaneous Quasiparticle Decay
• Quantum fluctuations in anisotropic triangular lattices with ferro- and antiferromagnetic exchange
• Emergence of string-valence bond solid state in the frustrated $J_1-J_2$ transverse field Ising model on the square lattice
• Quantum phase diagram of a frustrated antiferromagnet on the bilayer honeycomb lattice
• Softened magnetic excitations in the s = 3/2 distorted triangular antiferromagnet alpha-CaCr2O4
• Bose and Mott Glass Phases in Dimerized Quantum Antiferromagnets
• Entanglement entropy for the valence bond solid phases of two-dimensional dimerized Heisenberg antiferromagnets
• Mean-field theory of interacting triplons in a two-dimensional valence-bond solid: stability and properties of many-triplon states