Chemical potential tuning and strain engineering in topological half-Heusler thin films

Heusler compounds have emerged as an exciting material system where realization of functional and tunable novel topological phases might be possible. PtLuSb is one such compound that has recently been shown to host topologically non-trivial surface states. However, the chemical potential was found to lie below the Dirac point of the surface states, consistent with p-type Hall conductivity, in our thin films. One way to shift the chemical potential above the Dirac point is to substitute a few of the platinum (Pt) atoms in PtLuSb with gold (Au), which has one more electron compared to Pt. Employing a combination of the techniques of angle-resolved photoemission spectroscopy via a UHV vacuum suitcase transfer and in-situ scanning tunneling spectroscopy along with ex-situ transport measurements we will provide evidence of our ability to tune the chemical potential via substitution alloying in Pt_xAu_1-xLuSb thin films, in particular, the Fermi Level can be shifted close to the Dirac point for 38% Au concentration. In this talk, I will also present our efforts to synthesize bi-axially strained thin films on lattice mismatched substrate in order to lift the degeneracy of the Γ₈ manifold, thereby opening a bulk band gap in this otherwise semi-metallic compound.