Quantum triangular ice in the easy-axis ferromagnetic phase

Abstract

We use spin wave theory to investigate the ground state properties of the $Z_2$-invariant quantum XXZ model on the triangular lattice in the ferromagnetic phase. The Hamiltonian comprises nearest and next-nearest-neighbour Ising couplings, external magnetic fields, and a $Z_2$-invariant ferromagnetic coupling. We show that quantum fluctuations are suppressed in this system, hence linear spin wave theory gives reasonable estimates of the ground state thermodynamic properties. Our results show that, at half-filling (zero magnetic fields), the spontaneous breaking of $Z_2$ symmetry leads to a ferromagnetic phase whose energy spectrum is gapped at all excitations with a maxon dispersion at $\mathbf{k}=0$. This is in sharp contrast to rotational invariant systems with a vanishing phonon dispersion. We show that the $\mathbf{k}=0$ mode enhances the estimated values of the thermodynamic quantities. We obtain the trends of the particle density and the condensate fraction. The density of states and the dynamical structure factors exhibit fascinating peaks at unusual wave vectors, which should be of interest.

7 pages with 10 figures. Submitted for publication. arXiv admin note: substantial text overlap with arXiv:1511.01843

References in corpus (16)

• Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms
• Quantum Spin Ice: A Search for Gapless Quantum Spin Liquids in Pyrochlore Magnets
• Supersolid hardcore bosons on the triangular lattice
• Dynamically-Induced Frustration as a Route to a Quantum Spin Ice State in Tb2Ti2O7 via Virtual Crystal Field Excitations and Quantum Many-Body Effects
• Quantum spin ices and topological phases from dipolar-octupolar doublets on the pyrochlore lattice
• Valence Bond Solids and Their Quantum Melting in Hard-Core Bosons on the Kagome Lattice
• Is the Yb2Ti2O7 pyrochlore a quantum spin ice?
• Algebraic vortex liquid theory of a quantum antiferromagnet on the kagome lattice
• Extended supersolid phase of frustrated hard-core bosons on a triangular lattice
• Bosonic Many-body Theory of Quantum Spin Ice
• Supersolid Order of Frustrated Hard-Core Bosons in a Triangular Lattice System
• Proposal for a [111] Magnetization Plateau in the Spin Liquid State of Tb2Ti2O7
• Quantum Kagome Ice
• Variational wavefunction study of the triangular lattice supersolid
• A striped supersolid phase and the search for deconfined quantum criticality in hard-core bosons on the triangular lattice
• Simulations of Quantum XXZ Models on Two-Dimensional Frustrated Lattices

Cited by in corpus (2)

• Phases and collective modes of bosons in a triangular lattice at finite temperature: A cluster mean field study
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