Intermetallic Thin Films: A platform to create, control, and manipulate quantum matter

Intermetallic systems such as Heusler compounds, rare-earth monopnictides, heavy fermions, and iron-based superconductorsoffer an exciting playground to realize novel properties including exotic topological phases, tunable magnetic structures, unconventional superconductivity, and strongly correlated electronic phases.Our ability to synthesize these compounds in a thin film form opens up opportunities for potential technological applications inspintronics, thermoelectrics, plasmonics, and quantum computation.

In this talk, I will describe heteroepitaxial synthesis of two classes of intermetallic systems,viz. Heusler compounds and rare-earth monopnictideson III-V semiconductor substrates using molecular-beam epitaxy (MBE). 

Heusler compounds are a multi-functional class of ternary intermetallics that can be half-metallic, semiconducting, superconducting, and topologically non-trivial. I will present evidence for the presence of topologically non-trivial surface states in one such compound, PtLuSb. The chemical potentialin unintentionally doped samples of PtLuSb is found to lie below the Dirac point of the surface states, consistent with the p-type conductivity observed in Hall measurements. I will show that substitutional alloying of gold (Au) with platinum (Pt) in PtxAu1-xLuSb thin films can shift the chemical potential close to the Dirac pointwhenevidence of the presence of topological surface statesis manifested in transport measurements.

In the second part of the talk, I willdemonstrate epitaxial synthesis of thin films ofa rare-earth monopnictide compound,LuSb on a III-V semiconductor GaSb (001) substrates. Combining the techniques of MBE, low-temperature transport, angle-resolved photoemission spectroscopy ARPES), and hybrid density functional theory, we have unveiled the bandstructure of LuSb, where electron-hole compensation is identified as a mechanism responsible for the extreme magnetoresistance observed in this compound. I will show how the electronic structure of LuSbgets modified in thin film geometries and also depends sensitively on the incorporation of defects that can be controlled by tuning the growth parameters.

I will conclude by highlighting current efforts on synthesizing the cobalt (Co) based full Heusler compounds andelaborating on thebroad future prospects of the area.