8Li βNMR studies of Epitaxial Thin Films of the 3D topological Dirac semimetal Sr3SnO

Abstract

The inverse perovskite Sr3SnO is a 3D cubic Dirac semimetal with a very small energy gap[1]. Its unusual electronic structure confers a variety of novel properties, such as chiral topological surface states, and very strong itinerant electron orbital magnetism. Remarkably, when doped it also becomes superconducting[2]. In the lowest carrier density samples, the Fermi level lies close to the Dirac points, and orbital magnetism is maximal. Here we report the results of ion-implanted 8Li+ βNMR in Au-capped epitaxial thin films of Sr3SnO as a function of carrier content. In addition, we stop the 8Li in the Au overlayer to seek proximal evidence of the chiral surface state.In high magnetic field (6.55 T), we find remarkably little contrast in spin-lattice relaxation (SLR) between low carrier density Sr3SnO and the Au overlayer. In the inverse perovskite layer, 1/T 1 ∼ 0.14 s-1, slightly faster than Au at 300 K, while in the overlayer, there is a small but systematic enhancement in 1/T 1 compared to a control film of Au. The resonance in the Sr3SnO layer is broad with a long tail towards negative shift without resolved quadrupolar splitting.