title: Hybridization gap and Fano resonance in SmB6.
abstract: Hybridization between conduction electrons and the strongly interacting f-electrons in rare earth or actinide compounds may result in new states of matter. Depending on the exact location of the concomitant hybridization gap with respect to the Fermi energy, a heavy fermion or an insulating ground state ensues. To study this entanglement locally, we conducted scanning tunneling microscopy and spectroscopy (STS) measurements on the "Kondo insulator" SmB6. The vast majority of surface areas investigated were reconstructed, but infrequently, patches of varying sizes of nonreconstructed Sm- or B-terminated surfaces also were found. On the smallest patches, clear indications for the hybridization gap with logarithmic temperature dependence (as expected for a Kondo system) and for intermultiplet transitions were observed. On nonreconstructed surface areas large enough for coherent cotunneling, we were able to observe clear-cut Fano resonances. Our locally resolved STS indicated considerable finite conductance on all surfaces independent of their structure, not proving but leaving open the possibility of the existence of a topologically protected surface state.
authors.affiliation: Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany.
authors.forename: Sahana
authors.initials: S
authors.lastname: Rößler
authors.forename: Tae-Hwan
authors.initials: TH
authors.lastname: Jang
authors.forename: Dae-Jeong
authors.initials: DJ
authors.lastname: Kim
authors.forename: L H
authors.initials: LH
authors.lastname: Tjeng
authors.forename: Zachary
authors.initials: Z
authors.lastname: Fisk
authors.forename: Frank
authors.initials: F
authors.lastname: Steglich
authors.forename: Steffen
authors.initials: S
authors.lastname: Wirth