Tunable rotons in square lattice antiferromagnets under strong magnetic fields

Abstract

Excitation spectra of square lattice Heisenberg antiferromagnets in magnetic fields are investigated by the spin-wave theory. It is pointed out that a rotonlike structure appears in a narrow range of magnetic fields, as a result of strong nonlinear effects. It is shown that the energy gap and the mass of the "roton" are quite sensitive to the magnetic field: the roton gap softens rapidly and eventually closes as a precursor of a quantum phase transition. The possibility of the experimental observation of the roton and a new ground state after its softening are discussed.

9 pages, 6 figures

References in corpus (9)

• Spontaneous Magnon Decays
• Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet
• The antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field
• Magnon breakdown in a two dimensional triangular lattice Heisenberg antiferromagnet of multiferroic LuMnO${}_3$
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• Numerical evidence for unstable magnons at high fields in the Heisenberg antiferromagnet on the square lattice
• Large Negative Quantum Renormalization of Excitation Energies in the Spin-1/2 Kagome Lattice Antiferromagnet Cs${}_2$Cu${}_3$SnF${}_{12}$
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Cited by in corpus (3)

• Magnetic properties of quasi-two-dimensional $S$ = 1/2 Heisenberg antiferromagnet with distorted square lattice
• Torque equilibrium spin wave theory study of anisotropy and Dzyaloshinskii-Moriya interaction effects on the indirect K$-$ edge RIXS spectrum of a triangular lattice antiferromagnet
• Torque equilibrium spin wave theory of Raman scattering in an anisotropic triangular lattice antiferromagnet with Dzyaloshinskii-Moriya interaction