Hard-core boson approach to the spin−12 triangular-lattice antiferromagnet Cs2CuCl4 at finite temperatures in magnetic fields higher than the saturation field

Simon Streib, Peter Kopietz

arXiv:1507.04957Physical Review BSep 30, 201512 citations

Physica B Condensed Matter

Hard-core boson approach to S=1 magnets near saturation magnetic field

Hanting Wang

Published Feb 10, 2024• 1 citation

Publisher

DOI: 10.1016/j.physb.2024.415751

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Hard-core boson approach to the spin−12 triangular-lattice antiferromagnet Cs2CuCl4 at finite temperatures in magnetic fields higher than the saturation field

Simon Streib, Peter Kopietz

We study the high magnetic field regime of the antiferromagnetic insulator ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}$ by expressing the spin-1/2 operators in the relevant Heisenberg model in terms of hard-core bosons and implementing the hard-core constraint via an infinite on-site interaction. We focus on the case where the external magnetic field exceeds the saturation field ${B}_{c}\ensuremath{\approx}8.5\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ and is oriented along the crystallographic $a$ axis perpendicular to the lattice plane. Because in this case the excited states are separated by an energy gap from the ground state, we may use the self-consistent ladder approximation to take the strong correlations due to the hard-core constraint into account. In ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}$ , there are additional interactions besides the hard-core interaction which we treat in self-consistent Hartree-Fock approximation. We calculate the spectral function of the hard-core bosons from which we obtain the in-plane components of the dynamic structure factor, the magnetic susceptibility, and the specific heat. Our results for the specific heat are in good agreement with the available experimental data. We conclude that the self-consistent ladder approximation in combination with a self-consistent Hartree-Fock decoupling of the non-hard-core interactions gives an accurate description of the physical properties of gapped hard-core bosons in two dimensions at finite temperatures.We study the high magnetic field regime of the antiferromagnetic insulator ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}$ by expressing the spin-1/2 operators in the relevant Heisenberg model in terms of hard-core bosons and implementing the hard-core constraint via an infinite on-site interaction. We focus on the case where the external magnetic field exceeds the saturation field ${B}_{c}\ensuremath{\approx}8.5\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ and is oriented along the crystallographic $a$ axis perpendicular to the lattice plane. Because in this case the excited states are separated by an energy gap from the ground state, we may use the self-consistent ladder approximation to take the strong correlations due to the hard-core constraint into account. In ${\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}$, there are additional interactions besides the hard-core interaction which we treat in self-consistent Hartree-Fock approximation. We calculate the spectral function of the hard-core bosons from which we obtain the in-plane components of the dynamic structure factor, the magnetic susceptibility, and the specific heat. Our results for the specific heat are in good agreement with the available experimental data. We conclude that the self-consistent ladder approximation in combination with a self-consistent Hartree-Fock decoupling of the non-hard-core interactions gives an accurate description of the physical properties of gapped hard-core bosons in two dimensions at finite temperatures.

arXiv:1507.04957Physical Review BSep 30, 201512 citations

We study the high magnetic field regime of the antiferromagnetic insulator

{\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}

by expressing the spin-1/2 operators in the relevant Heisenberg model in terms of hard-core bosons and implementing the hard-core constraint via an infinite on-site interaction. We focus on the case where the external magnetic field exceeds the saturation field ${B}_{c}\ensuremath{\approx}8.5\phantom{\rule{0.28em}{0ex}}\mathrm{T}$ and is oriented along the crystallographic

a

axis perpendicular to the lattice plane. Because in this case the excited states are separated by an energy gap from the ground state, we may use the self-consistent ladder approximation to take the strong correlations due to the hard-core constraint into account. In

{\mathrm{Cs}}_{2}{\mathrm{CuCl}}_{4}

, there are additional interactions besides the hard-core interaction which we treat in self-consistent Hartree-Fock approximation. We calculate the spectral function of the hard-core bosons from which we obtain the in-plane components of the dynamic structure factor, the magnetic susceptibility, and the specific heat. Our results for the specific heat are in good agreement with the available experimental data. We conclude that the self-consistent ladder approximation in combination with a self-consistent Hartree-Fock decoupling of the non-hard-core interactions gives an accurate description of the physical properties of gapped hard-core bosons in two dimensions at finite temperatures.