2011/05/05 by Alexey V Sizanov, A. V. Sizanov, A. V. Syromyatnikov +1 · 19 citations
Physics and Astronomy · #Anisotropy #Condensed matter physics #Excitation #Ising model #Perturbation theory (quantum mechanics) #Physics #Physics of Superconductivity and Magnetism #Quantum #Quantum and electron transport phenomena #Quantum many-body systems #Quantum mechanics #Spectrum (functional analysis) #Spins #Statistical physics #cond-mat.str-el
paper · pdf · doi:10.1103/physrevb.84.054445
published in Physical Review B 84(5) (American Physical Society) · 15 pages, 8 figures
arxiv created 2011/05/05 · openalex publication_date 2011/08/12 · arxiv updated 2012/06/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We introduce a representation of an integer spin S via bosonic operators which is useful in describing the paramagnetic phase and transitions to magnetically ordered phases in magnetic systems with large single-ion easy-plane anisotropy D. Considering the exchange interaction between spins as a perturbation and using the diagram technique we derive the elementary excitation spectrum and the ground-state energy in the third order of the perturbation theory. In the special case of S=1 we obtain these expressions also using simpler spin representations some of which were introduced before. Comparison with results of previous numerical studies of 2D systems with S=1 demonstrates that our approach works better than other analytical methods applied before for such systems. We apply our results for the elementary excitation spectrum analysis obtained experimentally in NiCl2-4SC(NH2)2 (DTN). It is demonstrated that a set of model parameters (exchange constants and D) which has been used for DTN so far describes badly the experimentally obtained spectrum. A different set of parameters is proposed, using which we fit the spectrum and values of two critical fields of DTN.