Kondo interaction in FeTe and its potential role in the magnetic order.

Finding d-electron heavy fermion states has been an important topic as the diversity in d-electron materials can lead to many exotic Kondo effect-related phenomena or new states of matter such as correlation-driven topological Kondo insulator. Yet, obtaining direct spectroscopic evidence for a d-electron heavy fermion system has been elusive to date. Here, we report the observation of Kondo lattice behavior in an antiferromagnetic metal, FeTe, via angle-resolved photoemission spectroscopy, scanning tunneling spectroscopy and transport property measurements. The Kondo lattice behavior is represented by the emergence of a sharp quasiparticle and Fano-type tunneling spectra at low temperatures. The transport property measurements confirm the low-temperature Fermi liquid behavior and reveal successive coherent-incoherent crossover upon increasing temperature. We interpret the Kondo lattice behavior as a result of hybridization between localized Fe 3d_xy and itinerant Te 5p_z orbitals. Our observations strongly suggest unusual cooperation between Kondo lattice behavior and long-range magnetic order. The Kondo hybridization typically occurs in heavy-fermion systems containing f electrons, although recently it has been reported in d-electron systems. Kim et al. report spectroscopic evidence of the Kondo hybridization in FeTe and discuss it role in the mechanism of the magnetic order. [ABSTRACT FROM AUTHOR]