Thickness-tuned magnetotransport properties of topological semimetal trigonal PtBi2

Abstract

Here, we report systematic studies on thickness-dependent magnetotransport properties of trigonal layered PtBi2. When the thickness decreases, the metallicity is gradually suppressed, and it ultimately displays a semiconductor-like behavior when the thickness is reduced to 22 nm. Interestingly, the magnetoresistance (MR) decreases gradually as well as the thickness decreases, followed by an abrupt increase in the 22 nm nanoflake. The Hall resistance demonstrates the distinct evolution of an electronic state on thickness, revealing that the carrier compensation mechanism may play a role on the large MR in the 22 nm PtBi2 nanoflake. The scanning transmission electron microscopy image clearly uncovers the surface reconstruction of trigonal PtBi2, and qualitative interpretation is proposed for understanding the thickness-dependent transport properties. Our results provide insight into the electronic properties in the low-dimensional limit of topological semimetal trigonal PtBi2.