Unexpected magnetic phase in the weakly ordered spin-1/2 chain cuprate Sr2CuO3

Article

关键词: QUANTUM CRITICALITY;    NEEL TEMPERATURE;    FIELD;    ANTIFERROMAGNETS;    SUSCEPTIBILITY;    DYNAMICS;    S=1/2;   

DOI  :  10.1103/PhysRevB.101.201107

来源: SCIE

【 摘 要 】

The magnetic phase diagram of a spin-1/2 chain antiferromagnet Sr(2)CuO(3 )is studied by an ultrasound phase-sensitive detection technique. The system is in the extreme proximity of the Luttinger-liquid quantum-critical point and we observe an unusually strong effect of magnetic field, which is very weak compared to the in-chain interaction, on the Neel ordering temperature. Inside the ordered phase, we detect an unexpected, field-induced continuous phase transition. The transition is accompanied by softening of magnetic excitation observed by electron-spin resonance, which in previous work [E. G. Sergeicheva et al., Phys. Rev. B 95, 020411(R) (2017)] was associated with a longitudinal (amplitude) mode of the order parameter. These results suggest a transition from a transverse collinear antiferromagnet to an amplitude-modulated spin-density-wave phase in a very weak magnetic field, which is unexpected for a system of weakly coupled Heisenberg spin-1/2 chains.

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