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

Abstract

CeCoSi with no local inversion symmetric crystal structure ($P4/nmm$) exhibits a phase transition of unknown origin (Hidden Order: HO) at about 12 K ($T_0$) above the antiferromagnetic transition temperature ($T_{\mathrm{N}}=9.4$ K). The electronic structure change across $T_0$ was investigated with high-precision optical reflection spectroscopy. The optical spectrum changed from a typical metallic behavior above $T_0$ to a gap-like structure at around 15 meV below $T_0$. The gap-like structure was unchanged across $T_{\mathrm{N}}$ except for the narrowing of the Drude component of carriers due to the suppression of magnetic fluctuations. This result suggests a slight change from the typical metallic electronic structure above $T_0$ to that with an energy gap near the Fermi level in the HO phase. The change in electronic structure in the HO phase was concluded to be due to electron/valence instability.

5 pages, 4 figures

References in corpus (7)

• Field-induced transition from even to odd parity superconductivity in CeRh${}_2$As${}_2$
• NQR and NMR spectra in odd-parity multipole material CeCoSi
• Structural Transition in the Hidden Ordered Phase of CeCoSi
• Unusual Nonmagnetic Ordered State in CeCoSi Revealed by ${}^{59}$Co-NMR and NQR Measurements
• Optical Evidence of Itinerant-Localized Crossover of $4f$ Electrons in Cerium Compounds
• Magnetic field-Temperature Phase Diagram of CeCoSi Constructed by Specific Heat, Magnetoresistivity, and Magnetization Measurements for a Single Crystal
• Structural Phase Transition and Possible Valence Instability of Ce$-4f$ Electron Induced by Pressure in CeCoSi

Cited by in corpus (4)

• RKKY Interactions and Multipole Order in Ab initio Wannier Model of CeCoSi
• Three-stage Phase Transitions and Field-induced Phases in CeCoSi:A Landau Theory
• Microscopic Determination of the c-axis-Oriented Antiferromagnetic Structure in LaMnSi by ${}^{55}$Mn and ${}^{139}$La NMR
• Kondo-Peierls transition with nonsymmorphic zone boundary gap formation