2008/04/02 by T. Pardini, Rajiv R. P. Singh, R. R. P. Singh +3 · 12 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Anisotropy #Condensed matter physics #Heisenberg model #Ising model #Lattice (music) #Magnetic properties of thin films #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Spin (aerodynamics) #Spin wave #Square lattice #Thermodynamics #cond-mat.str-el #cond-mat.supr-con
paper · pdf · doi:10.1103/physrevb.78.024439
published in Physical Review B 78(2) (American Physical Society) · 6 pages, 3 figures
arxiv created 2008/04/02 · openalex publication_date 2008/07/29 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
Using series expansions and spin-wave theory, we calculate the spin-stiffness anisotropy \ensuremathρsx/\ensuremathρsy in Heisenberg models on the square lattice with spatially anisotropic couplings Jx,Jy. We find that for the weakly anisotropic spin-half model (Jx\ensuremath≈Jy), \ensuremathρsx/\ensuremathρsy deviates substantially from the naive estimate \ensuremathρsx/\ensuremathρsy\ensuremath≈Jx/Jy. We argue that this deviation can be responsible for pinning the electronic liquid crystal direction, an effect recently discovered in YBCO. For completeness, we also study the spin stiffness for arbitrary anisotropy Jx/Jy for spin-half and spin-one models. In the limit of Jy/Jx\ensuremath→0, when the model reduces to weakly coupled chains, the two show dramatically different behavior. In the spin-one model, the stiffness along the chains goes to zero, implying the onset of Haldane-gap phase, whereas for the spin-half model, the stiffness along the chains increases monotonically from a value of 0.18Jx for Jy/Jx=1 toward 0.25Jx for Jy/Jx\ensuremath→0. In the latter case, spin-wave theory breaks down qualitatively, presumably due to the onset of topological terms with strong anisotropy.