Research Projects

Kondo lattice systems are a class of strongly correlated system where interaction between delocalized conduction electrons and a periodic array of localized spin moments leads to the emergence of very flat bands close to the Fermi level. These compounds are of interest because they provide an ideal materials platform to realize several exotic quantum phenomena including pressure driven antiferromagnetic quantum phase transitions (QPT), unconventional superconductivity, strange metal phases, and strongly-correlated topological phases. However, there are several outstanding questions that remains unsettled and have been difficult to answer with traditional experimental probes on bulk single crystals. These include the nature of quantum critical fluctuations that drive QPT, direct phase sensitive measurements of the superconducting order parameter, the nature of quasiparticles in strange metal phases that emerge in the vicinity of a quantum critical point (QCP), and magnetotransport properties of a strongly correlated topological phase. To address these outstanding issues, we aim to synthesize epitaxial thin films of Kondo lattice systems CePd2Si2 and CePt2Si2. CePd2Si2 is known to undergo a pressure driven QPT and has a superconducting phase near the putative QCP. Synthesis of epitaxial thin films of CePd2Si2 on lattice-mismatched III-V semiconductor substrates will allow application of substrate induced bi-axial strain in-order to realize strain induced QPT. It will also allow access to pristine sample surfaces required for the investigation of quantum critical fluctuations and the momentum-resolved electronic structure by advanced spectroscopic probes such as time-domain terahertz spectroscopy (TDTS), angle-resolved photoemission spectroscopy (ARPES), and scanning tunnelling spectroscopy (STS) across such a strain driven QPT. Using top-down lithography techniques we aim to fabricate Josephson junctions to perform phase-sensitive measurements of the superconducting order parameter in CePd2Si2. Furthermore, shot noise measurements on lithographically defined nanowires of CePd2Si2 will allow direct measurements of granularity of charge carriers in the strange metals phase. All these measurements are currently not possible due to non-availability of CePd2Si2 in an epitaxial thin film form. CePt2Si2 has recently been predicted to host a Kondo-Weyl semimetallic phase, where Weyl nodes emerge as a consequence of the many-body Kondo effect. These phases are characterized by strong renormalization of quasiparticle velocities, which pushes the Weyl nodes close to the Fermi level. This proximity can result in pronounced Berry curvature - driven linear and non-linear responses in thermodynamic, thermoelectric, and transport properties - key aspects we aim to investigate. Notably, such a phase circumvents the usual challenge of tuning the chemical potential near the Weyl points, making these materials particularly promising for device applications that exploit the unique physics of Weyl nodes Finally, the emergence of spin-orbit coupled flat bands in momentum space can give rise to large spin-orbit torque and enhanced thermoelectric power factors. To harness these effects for spintronic and thermoelectric applications, it is essential to realize these compounds in an epitaxial thin film form - a key objective of this project. This will enable the integration of these material systems into advanced device architectures.