Magnetic Field–Temperature Phase Diagram of CeCoSi Constructed on the Basis of Specific Heat, Magnetoresistivity, and Magnetization Measurements: Single Crystal Study

Observation of Electronic Structure Modification in the Hidden Order Phase of CeCoSi

“…16) Experimentally, T 0 shifts to the high-temperature side and the anomaly at T 0 * kimura.shin-ichi.fbs@osaka-u.ac.jp becomes more pronounced by applying pressure, i.e., 38 K at 1.5 GPa 17,18) and also by applying magnetic field. 15) With these results, the symmetry of the Co site becomes lowering observed by NQR, 19) the crystal symmetry becomes lowering slightly detected by a synchrotron x-ray diffraction, 20) and the sign of the magnetic resistance changes at T 0 . 15) These results suggest that the electronic structure changes at T 0 , but direct evidence of the electronic structure modification in the HO phase has not been reported.…”

“…15) With these results, the symmetry of the Co site becomes lowering observed by NQR, 19) the crystal symmetry becomes lowering slightly detected by a synchrotron x-ray diffraction, 20) and the sign of the magnetic resistance changes at T 0 . 15) These results suggest that the electronic structure changes at T 0 , but direct evidence of the electronic structure modification in the HO phase has not been reported.…”

“…14) Recently, HO, in which the order parameter has not been revealed yet, has been observed at 12 − 13 K (T 0 ) higher than T N . 13,15) The origin is still unclear even though a theoretical work on the presence of odd-parity multipoles originating from staggered antiferromagnetic and antiferroquadrupole orderings has been proposed. 16) Experimentally, T 0 shifts to the high-temperature side and the anomaly at T 0 * kimura.shin-ichi.fbs@osaka-u.ac.jp becomes more pronounced by applying pressure, i.e., 38 K at 1.5 GPa 17,18) and also by applying magnetic field.…”

Electronic Nematic Ordering Driven by Atomic-scale Multipoles

“…In contrast to magnetic orderings, the breaking of time-reversal (T ) symmetry is not necessary, and hence, qualitatively distinct low-energy excitations and physical phenomena are expected. The electronic nematic states have been discussed in various contexts, such as the Pomeranchuk instability [4][5][6], spin nematic state [7][8][9][10][11][12][13][14], and charge/orbital nematic state [15][16][17][18][19][20][21], which have been observed in d-electron materials like Ba 2 MgReO 6 [22][23][24] and f -electron materials, such as CeB 6 [25][26][27][28], PrPb 3 [29][30][31], PrT 2 X 20 (T = Ir, Rh, X = Zn; T = V, X = Al) [32][33][34][35][36], and CeCoSi [37][38][39][40][41][42][43]. Recently, further exotic states coexisting spin and nematic orders have been suggested, such as the CP 2 skyrmion [44][45][46][47] and other multiple-Q states [48]…”