IQUIST Seminar: "Scanning NV Microscopy for Quantum Materials: From Magnetic Imaging to Nanoscale EPR", Huan Zhao, Eugene Wigner Distinguished Staff Fellow, Oak Ridge National Laboratory

"Scanning NV Microscopy for Quantum Materials: From Magnetic Imaging to Nanoscale EPR"

Abstract: Nitrogen-vacancy (NV) centers in diamond provide a powerful platform for nanoscale magnetic sensing, combining high spatial resolution with broad experimental compatibility. In this talk, I will briefly introduce the principles of scanning NV microscopy and then focus on two recent applications to quantum materials and spin systems. First, I will discuss scanning NV magnetometry using altermagnetic α-MnTe as an example, where nanoscale magnetic imaging reveals domain structures and their evolution under applied strain. I will then show how scanning NV relaxometry can be extended to nanoscale electron paramagnetic resonance (nano-EPR). Using spin defects in hexagonal boron nitride as a model system, cross-relaxation between the NV sensor and target spins enables local ESR spectroscopy and spatial mapping of spin-defect density without requiring direct optical readout of the target spins. I will conclude with ongoing work using quantum-logic-assisted repetitive readout to improve the sensitivity and imaging speed of scanning NV relaxometry. All work was conducted at the Center for Nanophase Materials Sciences (CNMS), a U.S. Department of Energy Office of Science user facility at Oak Ridge National Laboratory. I will also briefly introduce CNMS capabilities and the process for submitting a user proposal.

Bio: Dr. Huan Zhao is a research scientist at Oak Ridge National Laboratory (ORNL), where he conducts interdisciplinary research in spin-based quantum sensing, solid-state quantum light sources, nanomaterials, optical imaging, and nanoelectronics. He earned his Ph.D. in Electrical Engineering from the University of Southern California in December 2019. From 2019 to 2022, he was a Director’s Postdoctoral Fellow at the Center for Integrated Nanotechnologies at Los Alamos National Laboratory. He subsequently joined the Department of Medical Engineering at Caltech as a postdoctoral scholar, where he worked on ultrafast optical imaging. Since joining ORNL in December 2023, his research has primarily focused on solid-state single-photon sources and spin qubits. He also supports CNMS users conducting experiments with near-infrared spectroscopy systems and scanning NV microscopes.