Theoretical study of odd-parity multipole orders in CeCoSi*

Noncentrosymmetric systems have been attracted due to their fascinating phenomena, e.g., magneto-electric effects. We here focus on the electronic-order-driven inversion symmetry breaking in a centrosymmetric system. In this situation, noncentrosymmetric physical phenomena can be controllable through the spontaneous phase transitions. Besides, the odd-parity multipoles like magnetic toroidal dipole can be activated as unconventional electronic order parameters. The centrosymmetric f-electron compound CeCoSi has been recognized as the odd-parity multipole hosting material in its antiferromagnetic and nonmagnetic phases [1-3], although their origin has not been clarified. In the present study, we have investigated potential odd-parity multipole orders in CeCoSi and its physical phenomena including magneto-current and current-distortion effects [4]. Furthermore, we propose how to detect odd-parity multipoles through NQR/NMR measurement.
[1] E. Lengyel et al., Phys. Rev. B 88, 155137 (2013).
[2] H. Tanida et al., J. Phys. Soc. Jpn. 87, 023705 (2018); J. Phys. Soc. Jpn. 88, 054716 (2019).
[3] S. E. Nikitin et al., Phys. Rev. B 101, 214426 (2020).
[4] M. Yatsushiro and S. Hayami, J. Phys. Soc. Jpn. 89, 013703 (2020).