Magnetic Phase Diagram of Spin-1/2 Two-Leg Ladder with Four-Spin Ring Exchanges(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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We study a spin-1/2 two-leg Heisenberg ladder with four-spin ring exchanges under a magnetic field. We introduce an exact duality transformation, which is an extension of the spin-chirality duality developed previously and yields a new self-dual surface in the parameter space. We then determine the magnetic phase diagram using the numerical approaches of the density-matrix renormalization-group and exact diagonalization methods. We demonstrate the appearance of a magnetization plateau and a Tomonaga-Luttinger liquid with a dominant vector-chirality quasi-long-range order for a wide parameter regime of strong ring exchange. A "nematic" phase, in which magnons form bound pairs and magnon-pairing correlation functions dominate, is also identified.
社団法人日本物理学会の論文
2008-01-15