Correlated Quantum Phenomena at Superconductor/Magnetic Interfaces

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Nontechnical abstract: Quantum materials and related technology have been the driving force for giant breakthroughs in physics in the recent decades. For future progress in the field it is essential to understand quantum materials at the atomic level. This research project will focus on combining two quantum systems, namely ferromagnets (FMs) and superconductors (SCs), to enable intriguing scientific inquiries such as the appearance of Majorana pair modes and exotic spin triplet SCs. These topics will be experimentally investigated at cryogenic temperatures using advanced probes, leading to developing practical topological qubits and forming the basis for building a robust, scalable quantum computer. This work will impact quantum materials development, medicine, technology, finance, communication, and national security. The outcome of this multidisciplinary research project also has the potential for leading developments in highly energy-conserving superconducting spintronics, and for advancing quantum information science and engineering. In the process, postdocs and students at all levels would be trained at the forefront of quantum science/technology and material physics. The project will open up ample opportunities for initiating new theoretical and experimental collaborations worldwide, including advanced atomic level interface characterization at national laboratories. This will provide opportunities to the students including high school summer interns for scientific interaction with national and international scientists, and for enriching students' educational and outreach activities, both online and in-person.Technical Abstract: The project aims at investigating quantum phenomena at atomically resolved hybrid interfaces. Interface driven effects are pivotal in quantum materials study, a focus of this project. This study intends to understand and manipulate correlated effects in hybrid system by combining the quantum systems - ferromagnets (FMs) and superconductors (SCs) at the atomic level. This approach enables the study of signature interfacial exchange interaction, leading to establishing the Majorana bound state pair and their entanglement/teleportation, as well as the spin triplet Cooper pairing in SCs. Following the theoretical prediction, gold (111) surface state with its large spin orbit splitting in conjunction with a large gap SC, is an ideal platform for seeking the simultaneous Majorana pair appearance and understanding the parameters that define the intrinsic behavior/stability. For the triplet pair study the ferromagnetic Ni, EuS or GdN would be proximity-coupled to Ga, Bi or SCs such as Al or NbN, creating model systems for controlled study. To reach the goal, MBE-grown thin film heterostructures, scanning tunneling spectroscopy and high field as well as cryogenic magneto-transport studies would be carried out. The project will lead to a scalable, coherent topological qubit development, and an ideal dissipationless spin polarized source for superconducting spintronics, and the results will impact the field of quantum information science and engineering. Project involves postdocs and students to be trained in multidisciplinary areas at the forefront of quantum science, material physics and nanodevice technology. Opportunities are created for initiating theoretical and experimental collaborations worldwide in interface characterization at national laboratories. Outreach, education and broadening participation efforts in STEM address the needs of undergraduates and high school students, while promoting scientific education.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.