for Planar Tunneling Spectroscopy*

Previous works have utilized planar tunneling spectroscopy to investigate the possible topological surface states in SmB₆ [1,2]. When superconducting Pb is used as a counter-electrode, the tunneling conductance spectra revealed, coherence peaks with an asymmetrical temperature evolution as well as an additional peak at ~ 5 mV. These features were attributed to inelastic tunneling processes involving the emission and absorption of spin excitons [3,4]. The tunnel barrier in these reproducible junctions was formed by oxidizing the top layer of the SmB₆ [1,2]. Improving the junction quality even further, would allow for measurements of the second harmonic, which may reveal additional details about the spin excitons. The preparation of high-quality junctions on SmB₆ single crystals and thin films will be discussed. [1] W. K. Park et al., PNAS, 113, 6599 (2016). [2] L. Sun et al., Phys. Rev. B. 95, 195129 (2017). [3] W. T. Fuhrman et al., PRL 114, 036401 (2015). [4] G. A. Kapilevich et al., PRB 92, 085113 (2015).