물리학과에서는 아래와 같이 세미나를 개최하고자 하오니 관심있는 분들의 많은 참석 부탁드립니다.

Two rather disparate topics of ferromagnetism in the d-electron triple-layer strontium ruthenate, Sr4Ru3O10 and of a non-magnetic “hidden” order (HO) in the f-electron URu2Si2, are shown to have a common theme of the importance of van Hove singularities exhibiting strong electron correlation coherence behavior.

      For Sr4Ru3O10, spin- and angle-resolved photoemission (ARPES) reveal the low temperature electronic structure to be dominated by “two” strong intensity narrow bands at 30 meV below the Fermi-level at the Brillouin zone center and the zone boundary, but with opposite spin-polarization [1].  Both peaks exhibit dramatic temperature-dependent amplitude changes upon warming to the Curie temperature, which is proposed to relate to Hund-metal electron correlations.

     For URu2Si2, a shallow saddle-point band at the zone boundary N-point is proposed [2] to govern the underlying physics of a 35-year old puzzle of a non-magnetic 17.5K phase transition. Comparative changes of the N-point electronic structure for the various chemical-doping phase diagrams that do exhibit magnetic ordering provides proof of this model, including ARPES circular dichroism of an incommensurate-nested scattering process that demonstrates the existence of a helical ordering of f-orbitals in the HO phase. 

[1] P. Ngabonziza, J. D. Denlinger, A. Fedorov, G. Cao, J. W. Allen, G. Gebreyesus, and R. M. Martin, arXiv:2305.07222.

[2] J. D. Denlinger et al., Electronic Structure 4, 013001 (2022).