Elementary excitations in an S=1/2 antiferromagnetic chain KCuGaF

田中 秀数*; 栗田 伸之*; 梅垣 いづみ*; 小野 俊雄*; Laver, M.*; Niedermayer, Ch.*; Regg, Ch.*; 河村 聖子; 中島 健次; 加倉井 和久

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Neutron scattering experiments using AMATERAS at J-PARC in zero magnetic field and RITA-II at PSI in magnetic field have been performed to investigate elementary excitations in the S=1/2 antiferromagnetic spin chain system KCuGaF. The lower bound of magnetic excitations is well described by the des Cloizeaux and Pearson (dCP) mode and the spinon continuum above the dCP mode is observed.