Four-spin-exchange-driven chiral order in two-leg spin ladders under a magnetic field
Abstract Book of the XXIII IUPAP International Conference on Statistical Physics, Genova, Italy, (9-13 July 2007)Abstract
We discuss a new mechanism of a vector chiral long-range order in two-leg antiferromagnetic spin ladders with four-spin exchanges and a uniform Zeeman term. For one-dimensional quantum systems including ladders, generally, any continuous symmetries such as spin rotational one are not broken spontaneously. Therefore, it is believed that any vector chiral order is absent in $SU(2)$-symmetric spin ladders. However, if a uniform magnetic field is added along the spin z axis and the $SU(2)$ symmetry is reduced to a $U(1)$ one, z component of the vector chiral order can appear without breaking the continuous $U(1)$ symmetry. Utilizing Abelian bosonization techniques, we actually show that a certain type of four spin exchanges can induce a vector chiral order for the z axis in two-leg ladders under a magnetic field. \\
Reference: M.S, cond-mat/0703396\\
e-mail address: m$\_$sato@spring8.or.jp