Research Projects

An exciting research direction in condensed matter physics is exploring the theoretical basis and design principles for creating superconducting quantum nano-devices. In this context, heterostructure-based superconductors, such as the interface of Potassium tantalate (KTaO3 or KTO) with oxide overlayers has drawn a lot of attention as it shows several exotic phases including novel unconventional superconductivity. The recently discovered low-density superconductivity in (111)-oriented KTO interfaces with EuO is particularly interesting, which shows superconducting transition temperature almost 10 times higher than that found in other heterostructures. The surprising observation of such superconductivity with very low electron density and low superfluid stiffness suggest an interplay of superconductivity and disorder at the interface, as well as a strong dependence of the pairing on particular crystallographic orientation. Other key properties of KTO include high kinetic inductance, high dielectric constant and scalable with sub 10-nm nano-patternability. These make KTO an excellent candidate for constructing superconducting metamaterials by nano-patterning. While superconductors like Al or NbTiN with high electron densities have low kinetic inductances and rely on the Joshephson junctions for constructing nonlinear inductive elements and building superinductors, KTO offers a novel superconducting platform that intrinsically has very high inductance and enables the construction of metamaterials as it can be nano-patterned on length-scales comparable to the electron-electron separation due to its low electron density. Superinductors and designer nonlinear inductors can significantly improve the performance of superconducting quantum devices. Likewise, KTO is also an excellent candidate for fast-resetting single photon detectors over a wide range of wavelengths (from microwave to visible light), making it suitable for efficient superconducting qubits. The proposed research will theoretically study the effect of disorder, quantum fluctuations and pairing mechanism in this platform, using various advanced analytical and numerical tools like Quantum Monte Carlo simulations, Bogoliubov-de Gennes mean-field, dynamical quantum fluctuations. Our understanding will allow us to write effective symmetry based models in interfacial superconductors and connecting them to lumped circuit models with experimentally relevant parameters. We will also explore the nature and origin of the pairing, interplay of superconductivity, disorder and fluctuations, understanding dissipation mechanism [via calculation of Kinetic Inductance, Quality factors] which are important for next-generation applications, such as superconducting digital memory, single-photon detection, Terahertz radiation sources. Ultimately, this study will help control dynamical properties in not only KTO but related class of metamaterials, and hence push the limit on construction of quantum devices.