Composition-spread Growth and the Robust Topological Surface State of Kondo insulator SmB6 Thin Films

摘要

Topological insulators are a class of materials with insulating bulk butprotected conducting surfaces due to the combination of spin-orbit interactionsand time-reversal symmetry. The surface states are topologically non-trivialand robust against non-magnetic backscattering, leading to interesting physicsand potential quantum computing applications1, 2. Recently there has been afast growing interest in samarium hexboride (SmB6), a Kondo insulator predictedto be the first example of a correlated topological insulator3, 4. Here wefabricated smooth thin films of nanocrystalline SmB6 films. Their transportbehavior indeed shows that SmB6 is a bulk insulator with topological surfacestates. Upon decreasing the temperature, the resistivity \r{ho} of Sm0.14B0.86(SmB6) films display significant increase below 50 K due to hybridization gapformation, and it shows a saturation behavior below 10 K. The saturatedresistance of our textured films is similar to that of the single crystals,suggesting that this conduction is from the surface and robust against grainboundary scatterings. Point contact spectroscopy (PCS) of the film using asuperconducting tip displays both a Kondo Fano resonance and Andreevreflection, suggesting the existence of both an insulating Kondo lattice andmetallic surface states.