NQR and NMR spectra in the odd-parity multipole material CeCoSi

Abstract

We theoretically study NQR and NMR spectra in the presence of odd-parity multipoles originating from staggered antiferromagnetic and antiferroquadrupole orderings. For the f-electron metal, CeCoSi, which is a candidate hosting odd-parity multipoles, we derive an effective hyperfine field acting on Co nucleus generated from electronic origin multipole moments at Ce ion under zero and nonzero magnetic fields. We elucidate that emergent odd-parity multipoles give rise to sublattice-dependent spectral splittings in NQR and NMR through the effective hyperfine coupling in the absence of the global inversion symmetry. We mainly examine behaviors of the NQR and NMR spectra in three odd-parity multipole ordered states: a y-type magnetic toroidal dipole order with a staggered x-type antiferromagnetic structure, an xy-type electric toroidal quadrupole order with a staggered x 2 − y 2-type antiferroquadrupole structure, and a z-type electric dipole order with a staggered 3z 2 − r 2type antiferroquadrupole structure. We show that different odd-parity multipole orders lead to different fielddependent spectral splittings in NMR, while only the xy-type electric toroidal quadrupole order exhibits the NQR spectral splitting. We also present possible sublattice-dependent spectral splittings for all the odd-parity multipole orders potentially activated in low-energy crystal-field levels, which will be useful to identify oddparity order parameters in CeCoSi by NQR and NMR measurements.

Skyrmion crystal and spiral phases in centrosymmetric bilayer magnets with staggered Dzyaloshinskii-Moriya interaction

“…For example, the zigzag [91][92][93][94][95], honeycomb [96][97][98][99], and diamond [100][101][102] structures are typical prototypes with the sublattice-dependent DM interaction. Another example is a bilayer structure system where the sign of the DM interaction is opposite for the different two layers [103][104][105][106]. Although the above lattice structures with the sublattice degree of freedom have attracted great interest owing to the findings of an antiferromagnetic (AFM) SkX [107][108][109][110][111][112] and intriguing dynamics [113][114][115][116][117][118][119], the effect of the sublattice-dependent DM interaction on the stabilization of the SkX has not been fully clarified yet [120,121].…”

Magnetic Compton profile in non-magnetic ferroelectrics

“…The odd parity real-space charge multipoles and associated k-space MEMs also have implications in other physical effects beyond the MCP [46][47][48][49][50]. Examples include an exotic superconducting state driven by oddparity multipole fluctuations [51,52], and the predicted Rashba effect in PTO [53], which is a direct consequence of t (k) z .…”

Structural Phase Transition and Possible Valence Instability of Ce$-4f$ Electron Induced by Pressure in CeCoSi

“…4) It has been suggested that a possible origin for Phase II is an antiferroquadrupole ordering. 4,[8][9][10][11][12] Odd-parity multipole orderings originating from staggered AFM and antiferroquadrupole orderings have been proposed based on theoretical analyses. 8,9) A neutron powder diffraction study on CeCoSi shows that the magnetic moments of the two Ce atoms in the unit cell are antiferromagnetically ordered.…”