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TT: Fachverband Tiefe Temperaturen
TT 11: Heavy Fermions
TT 11.7: Talk
Monday, March 18, 2024, 16:45–17:00, H 3005
Magnetic adatoms as a probe for topological surface states in SmB6. — •Fabiola Neumann1, Michael Turaev1, and Johann Kroha1,2 — 1University of Bonn, DE — 2University of St. Andrews, UK
Recent scanning tunneling spectroscopy (STS) experiments on the surface of the predicted topological Kondo insulator SmB6 revealed that the peak in the local surface density of states (LDOS) is suppressed by a Gd impurity at the surface [1]. Surprisingly, this suppression extends spatially to a distance of several nm from the impurity, much larger than the range of the impurity potential. In the present work, we model the SmB6 bulk-surface heavy-fermion system by a layered auxiliary boson mean-field theory at temperature T=0, while the Gd impurity possesses a static spin s=7/2 in the 4f shell and a spin s=1/2 in the 5d shell. In particular, we investigate two possible scenarios for the LDOS suppression: (1) Coupling of the static Gd magnetic moment to the electron spin in the Dirac surface band by which the Dirac node acquires a gap [1], and (2) Local destruction of the SmB6 bulk topological heavy-fermion band by the time-reversal-breaking impurity which consequently removes the topological surface band. The latter mechanism may explain the long-range nature of the LDOS suppression via the Kondo coherence length ξK = vF/TK where vF is the Fermi speed and TK the Kondo temperature.
[1] L. Jiao et al., Sci. Adv. 4 (2018) eaau4886.
Keywords: Topological Kondo insulator; heavy fermion system; STM spectra; Topological surface states