Theory of electron spin resonance for detecting long-range spin nematic orders

The spin nematic phase is an interesting quantum magnetic phase where the bound magnon pair condenses. One of the most important issues around the topic of the spin nematic phase is how to detect the spin nematic order experimentally. Many theoretical proposals were made to resolve that issue. In particular, the inelastic neutron scattering cross section turned out to be an appropriate way of detecting the spin nematic order under the weak magnetic field [1]. On the other hand, since the spin nematic phase often emerges under the strong magnetic field, a methodology for detecting the spin nematic phase under strong fields is still strongly called for. In this presentation, we discuss that the electron spin resonance (ESR) spectrum is suitable for that purpose, that is, detection of the spin nematic order under strong fields. We show that the long-range spin nematic order generates a characteristic resonance peak that clearly reflects the condensation of the bound magnon pair.

[1] A. Smerald, H. T. Ueda, and N. Shannon, Phys. Rev. B 91, 174402 (2015).
[2] S. C. Furuya and T. Momoi, arXiv:1707.08784