Kondo entanglement in the quasi-two-dimensional heavy fermion compound CeSb2

In the heavy fermion system, development of the Kondo coherence usually occurs as a crossover behavior. However, accurate definition of the onset temperature for complete formation of the heavy quasiparticles is to some extent controversial. Here, the electronic structure of the quasi-two-dimensional Kondo lattice CeSb2 has been studied by high resolution angle-resolved photoemission spectroscopy (ARPES) and dynamical meanfield theory approach combined with density functional theory. A heavy quasiparticle band, which originates from the hybridization between f electrons and conduction electrons, has been observed directly. Moreover, temperature-dependent electronic structure study reveals a transition from high-temperature local spins to lowtemperature itinerant electrons in CeSb2 and the onset temperature of the hybridized c-f spectral weight revealed by laser-ARPES is consistent with the crossover temperature from transport and magnetic measurements. Our findings are essential for a microscopic understanding of different energy scales in the heavy fermion system and demonstrate the probability of laser-ARPES in studying the bulk 4f-electron properties of Ce-based compounds.