Two-dimensional heavy fermion in a monoatomic-layer Kondo lattice YbCu_2
arXiv (Cornell University)(2023)
摘要
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 [S. Sachdev, Science 288, 475 (2000)]. However, perfect
two-dimensional (2D) HF materials have not been reported yet. Here, we report
the surface electronic structure of the monoatomic-layer Kondo lattice YbCu_2
on a Cu(111) surface observed by synchrotron-based angle-resolved photoelectron
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 coherent
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 coherent temperature. Our
study provides a new candidate as an ideal 2D HF material for understanding the
Kondo effect at low dimensions.
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关键词
lattice
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