Collective Modes and Quantum Transport in Quantum Materials

Research Project, 2020 – 2023

Recent progress in materials science has produced several new classes of materials and heterostructures with very interesting properties, either related to strongly correlated electron physics or topology. Examples cover high-temperature superconductors, two-dimensional materials beyond graphene, and the superconducting two-dimension electron gas at the interface between LaAlO3 and SrTiO3. A common theme is strong spin-orbit coupling and/or electron-electron interactions pushing the electron system to be close to a phase transition, either of Landau-Ginzburg or of topological type. In this project we will explore the electronic transport properties of these quantum materials in device geometries, including contacts to outside reservoirs, with a focus on superconducting quantum materials. The inhomogeneous superconducting state will lead to excitation of collective modes of the order parameter that we will investigate. Our tools will be analytic and numerical. A substantial part of the project is development of our existing state-of-the-art computational and simulation tools: 1) a solver for the quasiclassical Green’s functions for layered unconventional superconductors with complex 2D geometry, massively parallelized, running on graphics cards (GPUs); 2) a non-equilibrium Green’s function based quantum transport solver utilizing a knitting algorithm for tight-binding Hamiltonians for general geometries and arbitrary number of leads; running on CPUs, parallelized with MPI.