Revealing Exotic Magnetism through Spin Transport

======= Abstract =======
Recent advances in quantum sensing and optical techniques have opened new experimental access to spin transport in quantum materials and excited further theoretical investigation of spin transport in exotic magnets. In this talk, I will discuss two examples of spin transport theory developed to probe unconventional magnetism. First, in frustrated triangular-lattice magnets, finite-temperature spin dynamics in the correlated paramagnetic regime is studied, where spin diffusion emerges in the absence of quasiparticles with well-defined momenta. Classical spin dynamics, stochastic diffusion theory, and finite-temperature quantum calculations consistently reveal a strong suppression of spin conductivity and spin diffusion constant in the highly frustrated regime, identifying spin transport as a diagnostic of proximate spin-liquid behavior. Second, in altermagnetic insulators, nonlinear optical charge and spin photocurrents provide a symmetry-selective probe of spin-resolved electronic structure. Spin-group-symmetry breaking, induced for example by shear strain, generates spin-gap asymmetry and activates otherwise forbidden photocurrent components whose signs are locked to the symmetry-breaking perturbation. Together, these examples show how spin transport can reveal hidden magnetic correlations, symmetry breaking, and emergent collective behavior in quantum materials.

=============== About the Speaker ===============
Shu Zhang is an Assistant Professor at Okinawa Institute of Science and Technology Graduate University, leading the research unit “Collective Dynamics and Quantum Transport”. She obtained her Ph.D. in theoretical condensed matter physics from Johns Hopkins in 2019 and was a Graduate Fellow at Kavli Institute for Theoretical Physics in University of California, Santa Barbara. She has previously held academic positions as a postdoc in University of California, Los Angeles, a Distinguished PKS Postdoctoral Fellow at Max Planck Institute for the Physics of Complex Systems, and a Junior Group Leader in Leibniz Institute for Solid State and Materials Research, Dresden, Germany. Her research focuses on emergent dynamic and transport phenomena in quantum materials and platforms.