Magnetotransport and Shubnikov-de Haas oscillations in LaBi samples with different degrees of air exposure

Abstract

A series of magnetotransport experiments has been designed to investigate single-crystalline LaBi samples subjected to different degrees of air exposure. As the air exposure time increases, the temperature-dependent resistance changes from the typical behaviour of a good metal to that of a bad metal, exhibiting a negative temperature coefficient. Additionally, the magnetoresistance in the sample with the longest air exposure becomes linear in the magnetic field, instead of the ubiquitous quadratic magnetoresistance observed in many other related rare-earth monopnictides. Despite these drastic changes, the Shubnikov-de Haas oscillations remain almost unaffected by air exposure – the frequency spectra and the effective masses do not vary as the air exposure time increases. Our results suggest the existence of two separate contributions to the transport data: one from the surface and the other from the bulk. Given the topological nature of LaBi, our results suggest controlled air exposure provides an effective means to distinguish between surface and bulk states.