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

Journal Nat. Commun. 14(1):7850 (2023)
Title Two-dimensional heavy fermion in monoatomic-layer Kondo lattice YbCu2
Laboratory Photophysics Laboratory〈Prof. KIMURA Shin-ichi〉
Abstract

The Kondo effect between localized f-electrons and conductive carriers leads to exotic physical phenomena. Among them, heavy-fermion (HF) systems, in which massive effective carriers appear due to the Kondo effect, have fascinated many researchers. Dimensionality is also an important characteristic of the HF system, especially because it is strongly related to quantum criticality. However, the realization of the perfect two-dimensional (2D) HF materials is still a challenging topic. Here, we report the surface electronic structure of the monoatomic-layer Kondo lattice YbCu2 on a Cu(111) surface observed by synchrotron-based angle-resolved photoemission spectroscopy. The 2D conducting band and the Yb 4f state, located very close to the Fermi level, are observed. These bands are hybridized at low-temperature, forming the 2D HF state, with an evaluated coherence temperature of about 30 K. The effective mass of the 2D state is enhanced by a factor of 100 by the development of the HF state. Furthermore, clear evidence of the hybridization gap formation in the temperature dependence of the Kondo-resonance peak has been observed below the coherence temperature. Our study provides a new candidate as an ideal 2D HF material for understanding the Kondo effect at low dimensions.

Authors

Takuto Nakamura (1, 2), Hiroki Sugihara (2), Yitong Chen (2), Ryu Yukawa (4), Yoshiyuki Ohtsubo (5), Kiyohisa Tanaka (6), Miho Kitamura (7), Hiroshi Kumigashira (8), Shin-Ichi Kimura (1, 2, 6)

  1. Graduate School of Frontier Biosciences, Osaka University, Suita, 565-0871, Japan.
  2. Department of Physics, Graduate School of Science, Osaka University, Toyonaka, 560-0043, Japan.
  3. Graduate School of Engineering, Osaka University, Suita, 565-0871, Japan.
  4. National Institutes for Quantum Science and Technology, Sendai, 980-8579, Japan.
  5. Institute for Molecular Science, Okazaki, 444-8585, Japan.
  6. Photon Factory, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, 305-0801, Japan.
  7. Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai, 980-8577, Japan.
PubMed 38040781

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