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    Please use this identifier to cite or link to this item: http://nccur.lib.nccu.edu.tw/handle/140.119/64828

    Title: Correlated valence-bond states
    Authors: 林瑜琤;Y. Tang;J. Lou;A.W. Sandvik
    Lin, Yu-Cheng;Tang, Ying;Lou, Jie;Sandvik, Anders W.
    Contributors: 應物所
    Date: 2012.10
    Issue Date: 2014-03-21 18:01:38 (UTC+8)
    Abstract: We study generalizations of the singlet-sector amplitude-product (AP) states in the valence-bond basis of S=1/2 quantum spin systems. In the standard AP states, the weight of a tiling of the system into valence bonds (singlets of two spins) is a product of amplitudes depending on the length of the bonds. We here introduce correlated AP (CAP) states, in which the amplitude product is further multiplied by factors depending on two bonds connected to a pair of sites (here nearest neighbors). While the standard AP states can describe a phase transition between an antiferromagnetic (Neel) state and a valence-bond solid (VBS) in one dimension (which we also study here), in two dimensions it cannot describe VBS order. With the CAP states, Neel-VBS transitions are realized as a function of some parameter describing the bond correlations. We here study such phase transitions of CAP wave-functions on the square lattice. We find examples of direct first-order Neel-VBS transitions, as well as cases where there is an extended U(1) spin liquid phase intervening between the Neel and VBS states. In the latter case the transitions are continuous and we extract critical exponents and address the issue of a possible emergent U(1) symmetry in the near-critical VBS. We also consider variationally optimized CAP states for the standard Heisenberg model in one and two dimensions and the J-Q model in two dimensions, with the latter including four-spin interactions (Q) in addition to the Heisenberg exchange (J) and harboring VBS order for large Q/J. The optimized CAP states lead to significantly lower variational energies than the simple AP states for these models.
    Relation: Physical Review B, 86(14), 144405(1-20)
    Data Type: article
    DOI 連結: http://dx.doi.org/10.1103/PhysRevB.86.144405
    DOI: 10.1103/PhysRevB.86.144405
    Appears in Collections:[應用物理研究所 ] 期刊論文

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