Research Topics
Topological phenomena in Heusler alloys and heterostructures
Heusler alloys are a remarkable class of multi-functional inter-metallic compounds with properties ranging from superconductivity to half-metallic ferromagnets. We are investigating novel topological phases in Heusler alloy thin films and their heterostructures, both in the momentum and in the real space.
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more than 1000s of possible combinations!
In the momentum space, theory predicts the existence of topological semimetal, nodal lines, Dirac fermions, triple-point fermions, and time-reversal symmetry breaking Weyl states, remarkably, all within the same material family. Thin film geometries offer new routes to control these material properties in addition to the well-established chemical route via tuning the number of valence electrons.
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In the real space, non-trivial winding of magnetic moment can lead to topologically stable magnetic structures known as skyrmions. Heusler thin films and heterostructures offer unparalleled tunability of magneto-crystalline anisotropy, magnetization, inversion symmetry breaking, and spin-orbit coupling, providing exquisite control over Dzyaloshinskii - Moriya (D-M) interaction that can lead to the appearance of new skyrmion phases and applications in novel device geometries such as race-track memory. In addition, we plan to exploit wide tunability in magnetic interactions in Heusler compounds to design novel compensated antiferromagnets and artificial heterostructures with non-collinear spin structure that promise wide-ranging spintronic applications.
Mixed-valence and heavy fermionic compounds provide an ideal material platform to study quantum phase transition, unconventional superconductivity, and the interplay of strong correlations and topological order, such as the recently predicted Kondo-Weyl semimetallic phase.
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We aim to synthesize these materials in a thin-film form that remains poorly explored, but promises several exciting opportunities that we would pursue. Below are two such examples that offers a flavor of the kind of opportunities that exist.
Access to pristine sample surfaces in thin films makes it possible to perform advanced spectroscopy measurements, such as ARPES, without the requirement of cleaving, which will allow us to address outstanding fundamental issues regarding the emergence of coherence in heavy fermion compounds and the nature of the mixed-valence phenomena in a wide variety of material systems that have hitherto remained out-of-reach. Recently, we have shown first successful implementation of such an approach to understand Lifshitz transition driven by mixed-valence phenomena.
Thin film geometries opens up the possibility of revealing new functionalities of these compounds. In a recent work, we have revealed the utility of heavy fermion systems in designing charge-to-spin current conversion technologies for spintronic applications where, a giant spin-hall conductivity is achieved, driven by the Kondo physics in these materials.
Mixed valence and heavy fermion systems
Artificial hybrid quantum materials
Our bottoms-up approach to materials fabrication provides unique opportunity to combine disparate material properties to realize emergent quantum phenomena and novel functionalities in artificial heterostructures. We are primarily interested in superconductor-topological systems, superconductor-semicondictor, and topological systems-ferromagnet hybrids to realize new platforms for topological superconductivity aimed at topological quantum computing, quantized versions of anomalous and spin hall effect at elevated temperatures, and for applications in spintronics devices.