Quantum phase transition and magnetic excitation in the =1/2 Ising-like antiferromagnetic chain CsCoCl in transverse magnetic fields

横磁場下=1/2イジング様反強磁性鎖CsCoClにおける量子相転移と磁気励起

木村 尚次郎*; 大西 弘明  ; 鳴海 康雄*; 奥西 巧一*; 萩原 政幸*; 金道 浩一*; 菊池 彦光*

Kimura, Shojiro*; Onishi, Hiroaki; Narumi, Yasuo*; Okunishi, Koichi*; Hagiwara, Masayuki*; Kindo, Koichi*; Kikuchi, Hikomitsu*

We have performed high-field electron spin resonance (ESR) measurements on the =1/2 Ising-like one-dimensional (1D) antiferromagnet CsCoCl in the frequency range up to 3.1 THz and magnetic fields for up to 53 T, as well as density-matrix renormalization group (DMRG) calculations. The analysis of the high-field magnetization confirms that the quantum critical point in the transverse field is = 60.3 T. The results of the ESR measurements suggest the remarkable behavior that all the excitation branches coming from the Zeeman ladder converge to upon increasing the transverse fields. The ESR measurements with polarized electromagnetic waves show that the ESR absorption lines show clear polarization dependence. The absorption lines, which become soft in the transverse field, are revealed to couple with the magnetic field oscillating parallel to the static magnetic fields. These experimental results are compared with the detailed DMRG calculations.