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arXiv 1107.0772cond-mat.str-el
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磁场中的变形三角晶格反铁磁体:空间各向异性和Dzyaloshinskiii-Moriya相互作用的作用

Deformed triangular lattice antiferromagnets in a magnetic field: role of spatial anisotropy and Dzyaloshinskii-Moriya interactions

Christian Griset, Shane Head, Jason Alicea, Oleg A. Starykh

摘要:

最近对自旋为1/2的各向异性三角形反铁磁体Cs_2CuBr_4的实验表明,在外加磁场中,其相图由大量的有序相组成。基于这一发现,我们研究了空间各向异性,Dzyaloshinskiii-Moriya相互作用和量子涨落对三角形反铁磁体磁化过程的作用,来自半经典极限。这个问题的丰富性源于两个关键事实:1)经典的各向同性模型表现出很大的偶然基态简并,2)这三种成分相互竞争,并以相反的方式分裂这种简并。使用各种互补的方法,包括广泛的Monte Carlo数值,自旋波理论,并在高场的磁振子的玻色-爱因斯坦凝聚的分析,我们发现,它们的相互作用产生了一个复杂的相图,由许多无公度和公度相。我们的研究结果揭示了所观察到的Cs_2CuBr_4相图,并提出了一些未来的理论和实验方向,这将是有用的,以获得一个完整的理解这种材料的有趣的现象。

英文摘要:

Recent experiments on the anisotropic spin-1/2 triangular antiferromagnet Cs_2CuBr_4 have revealed a remarkably rich phase diagram in applied magnetic fields, consisting of an unexpectedly large number of ordered phases. Motivated by this finding, we study the role of spatial anisotropy, Dzyaloshinskii-Moriya interactions, and quantum fluctuations on the magnetization process of a triangular antiferromagnet, coming from the semiclassical limit. The richness of the problem stems from two key facts: 1) the classical isotropic model exhibits a large accidental ground state degeneracy, and 2) these three ingredients compete with one another and split this degeneracy in opposing ways. Using a variety of complementary approaches, including extensive Monte Carlo numerics, spin-wave theory, and an analysis of Bose-Einstein condensation of magnons at high fields, we find that their interplay gives rise to a complex phase diagram consisting of numerous incommensurate and commensurate phases. Our results shed light on the observed phase diagram for Cs_2CuBr_4 and suggest a number of future theoretical and experimental directions that will be useful for obtaining a complete understanding of this material's interesting phenomenology.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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