Two-dimensional heavy fermion in a monoatomic-layer Kondo lattice YbCu₂

日時　2023年11月8日　（水）　16：30～17：45
場所　広島大学放射光科学研究センター　2階　セミナー室
講師　Shin-ichi Kimura
(Osaka University and Institute for Molecular Science, Japan)

The dimensionality is an important parameter for tuning physical properties in strongly correlated electron systems [1]. Even in heavy fermions (HFs), tuning the dimensionality is a challenging issue because of the intermetallic compounds. So far, some trials to fabricate atomic layered heavy fermion have been performed, one is the superlattice heterostructure of CeIn₃ and LaIn₃ fabricated by a molecular-beam epitaxy method [2]. With decreasing thickness, the coherent temperature T_coh, which is a mark of the Kondo effect, shifts to the low-temperature side, suggesting the closing to the quantum critical point. Here, we introduce our recent trial to establish mono-atomic layered HFs in YbM₂ (M: Cu, Ag, Au). Among YbM₂, the mono-atomic layered YbCu₂ on a Cu(111) surface shows a HF character in the electronic structure with synchrotron-based angle-resolved photoelectron spectroscopy [3]. The two-dimensional (2D) conduction band and the Yb 4f state are observed near the Fermi level. These bands are hybridized at lower temperatures than ~100 K, forming a 2D HF state, with an evaluated T_coh of about 30 K. Furthermore, clear evidence of the hybridization gap formation in the temperature dependence of the Kondo-resonance peak has been observed below T_coh. These results strongly suggest that YbCu₂ on Cu(111) is a monoatomic layered HF material.

[1] S. Sachdev, Science 288, 475 (2000).
[2] H. Shishido et al., Science 327, 980 (2010).
[3] T. Nakamura, sk et al., arXiv: 2306.06984.

問合せ先　出田真一郎（放射光科学研究センター）