2017/04/30 by Daisuke Yamamoto, Hiroshi Ueda, Ippei Danshita +3 · 30 citations
Mathematics · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Cluster (spacecraft) #Combinatorics #Computer science #Condensed matter physics #Hexagonal lattice #Lattice (music) #Mathematical physics #Mathematics #Physics #Physics of Superconductivity and Magnetism #Saturation (graph theory) #Statistical physics #Theoretical and Computational Physics #cond-mat.stat-mech #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.96.014431
published in Physical review. B./Physical review. B 96(1), 014431 (American Physical Society) · 13 pages, 13 figures
openalex publication_date 2017/07/25 · arxiv created 2017/07/30 · arxiv updated 2017/08/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Quantum magnetic phases near the magnetic saturation of triangular-lattice antiferromagnets with XXZ anisotropy have been attracting renewed interest since it has been suggested that a nontrivial coplanar phase, called the \ensuremathπ-coplanar or \mathrm\ensuremathΨ phase, could be stabilized by quantum effects in a certain range of anisotropy parameter J/Jz besides the well-known 0-coplanar (known also as V) and umbrella phases. Recently, Sellmann et al. [Phys. Rev. B 91, 081104(R) (2015)] claimed that the \ensuremathπ-coplanar phase is absent for S=1/2 from an exact-diagonalization analysis in the sector of the Hilbert space with only three down-spins (three magnons). We first reconsider and improve this analysis by taking into account several low-lying eigenvalues and the associated eigenstates as a function of J/Jz and by sensibly increasing the system sizes (up to 1296 spins). A careful identification analysis shows that the lowest eigenstate is a chirally antisymmetric combination of finite-size umbrella states for J/Jz\ensuremath\gtrsim2.218 while it corresponds to a coplanar phase for J/Jz\ensuremath\lesssim2.218. However, we demonstrate that the distinction between 0-coplanar and \ensuremathπ-coplanar phases in the latter region is fundamentally impossible from the symmetry-preserving finite-size calculations with fixed magnon number. Therefore, we also perform a cluster mean-field plus scaling analysis for small spins S\ensuremath≤3/2. The obtained results, together with the previous large-S analysis, indicate that the \ensuremathπ-coplanar phase exists for any S except for the classical limit (S\ensuremath→\ensuremath∞) and the existence range in J/Jz is largest in the most quantum case of S=1/2.