標題： 理論セミナー：Boundary bound states in spin-1/2 antiferromagnetic chains
日時： 2011年11月25日(金) 午後4:00〜午後5:00
場所： 物性研究所本館6階 第5セミナー室（A615）
講師： 古谷 峻介 氏
要旨： Several gapped one-dimensional quantum antiferromagnets can be described by integrable field theories. Elementary excitations in these systems are well understood despite their strongly correlated nature, and this has been verified in numerous experiments. Impurity problems are another fascinating issue in quantum many-body systems.In gapless one-dimensional systems with impurities, boundary conformal field theory leads to interesting consequences such as edge anomalies of the magnetic susceptibility and the NMR relaxation rate. In gapped spin chains, on the other hand, the elementary excitations can form bound states localized at the boundary.
We point out that a spin-1/2 antiferromagnetic Heisenberg chain with a staggered magnetic field can be described by an integrable field theory even in the presence of the boundary, and its exact solution contains the “boundary bound states”.We identify the previously unaccounted resonances observed in ESR spectra of KCuGaF6 and Cu-PM, with the boundary bound states.This might be the first experimental observation of the boundary bound states.