MBE Grown Bismuth Thin Films for Hydrodynamic Transport Studies

In quantum many-body systems, interactions between particles can lead to electron transport behaving as viscous liquid flow that is governed by hydrodynamic equations. The hydrodynamic regime is entered when the length scales are shorter than the electron mean-free path. Bi has long been known for its unusual electronic properties due to its low carrier concentration, small carrier effective mass, and long carrier mean free paths, making it a strong candidate to study for the hydrodynamic physics. In this work, we probe the signatures of hydrodynamic transport in MBE grown Bi films. Varying thickness of Bi films are grown epitaxially on Bi₂Te₃ with Al₂O₃ substrates. The few nanometer Bi₂Te₃ buffer layer allows wetting of the Bi film which does not occur on the oxide substrate. The films are then patterned by electron beam lithography and etched by Ar plasma to channels as narrow as hundreds of nanometer wide. Because the channel width is narrower than the electron mean-free path, a shear force induced by viscosity is expected at the channel walls to make electron velocity profile of a Stokes flow and resistivity varies with the square of the channel width. The results of these experiments as well as analysis of the SdH oscillations of the Bi channels will be presented.