Phonon-Mediated Physics in Quantum Systems

Abstract: Phonons define the landscape of all condensed matter systems. From mediating superconductivity to dissipating quantum information, the phonon lattice is the medium through which the most compelling phenomena in our field manifest. In this talk, I will discuss how we navigate this landscape through two experimental frontiers in my lab. First, we explore anomalous thermoelectricity in superconductor-ferromagnet (S-F) hybrids. While superconductors are traditionally poor thermoelectrics due to their inherent electron-hole symmetry, S-F hybrids are predicted to break this symmetry, potentially becoming the only efficient thermoelectric materials at cryogenic scales. I will present our development of on-chip measurement techniques and our direct observation of Seebeck voltages in S-F structures down to 8 mK. Second, we investigate the "omnipresent phonon bath" in Si-Ge quantum dots. Controlling the coupling between spins and the lattice is the key to designing "hot" qubits and next-generation spintronic devices, as spin-phonon interactions drive both decoherence and relaxation. I will share our progress in designing a mechanical strain stage (see figure) to intentionally modify this coupling in Intel-fabricated Si-Ge quantum dot chips, aiming to engineer more robust qubits.

 

Speaker Bio: Dr. Singh is an Associate Professor of Physics and Director of the Quantum Engineering program at the Colorado School of Mines. She received her Ph.D. in Physics from Penn State University, where she studied superconducting nanowires, followed by postdoctoral research at Sandia National Laboratories focused on silicon spin qubits. Since joining Mines in 2017, she has led an interdisciplinary research program spanning quantum physics, condensed matter, and materials science. Her current projects include exploring chirality-induced spin selectivity and raising the operating temperatures of silicon spin qubits. Her work has been recognized with an NSF CAREER Award (2021–2026) and a Fulbright-Nehru Academic and Professional Excellence Award (2023–2024).