Vector-spin-chirality order in a dimerized frustrated spin-1/2 chain

Article

关键词: MATRIX RENORMALIZATION-GROUP;    HEISENBERG LADDER;    PHASE-TRANSITIONS;    MODEL;   

DOI  :  10.1103/PhysRevB.89.024407

来源: SCIE

【 摘 要 】

A frustrated spin-1/2 XXZ chain model comprising a ferromagnetic nearest-neighbor coupling with the bond alternation, J(1)(1 +/- delta) < 0, and an antiferromagnetic second-neighbor exchange coupling J(2) > 0 is studied at zero and weak magnetic fields by means of density-matrix renormalization-group calculations of order parameters, correlation functions, and the entanglement entropy, as well as an Abelian bosonization analysis. At zero magnetic field, the bond alternation delta > 0 suppresses the gapless phase characterized by a vector-chiral (VC) long-range order (LRO) and a quasi-LRO of an incommensurate spin spiral, whereas this phase occupies a large region in the space of J(1)/J(2) and the easy-plane exchange anisotropy for delta = 0 [S. Furukawa et al., Phys. Rev. Lett. 105, 257205 (2010)]. Then, four gapped phases are found to appear as the exchange anisotropy varies from the SU(2)-symmetric case to the U(1)-symmetric case: the Haldane dimer (D+) phase with the same sign of the x, y- and z-component dimer order parameters, two VC dimer (VCD+/VCD-) phases with the sign of the z-component dimer order parameter being unaltered/reversed, and the even-parity dimer (D-) phase. At small magnetic fields, a field-induced ring-exchange interaction, which is proportional to a staggered scalar chirality and a magnetic flux penetrating the associated triangle, drives a transition from the D- phase into a VC-Neel-dimer (VCND) phase, but not from the D+ phase. This VCND phase is stable up to the large magnetic field at which the Zeeman term closes the spin gap. A possible relevance to Rb2Cu2Mo3O12 is discussed.

【 授权许可】

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