题目：A Theoretical Framework for Intrinsic and Extrinsic Nonlinear Electrical, Spin, and Thermoelectric Responses
摘要：In recent years, nonlinear transport phenomena have garnered significant interest in both theoretical explorations and experiments. This talk presents our systematic investigations in the field of nonlinear transport, covering multiple aspects ranging from symmetry constraints and new physical mechanisms to material realizations. First, we perform a comprehensive symmetry analysis of all 122 magnetic point groups, systematically deriving the nonlinear response tensors for charge and spin transport arising from the Berry curvature dipole, Berry connection polarizability, and Drude contributions. This work provides a theoretical dictionary for second-order nonlinear transport in various magnetic materials. Second, we propose a mechanism for dynamic spin generation driven by time-varying electric fields. In nonmagnetic insulators, the time derivative of the electric field can induce linear spin polarization via the first-order dynamic anomalous spin polarizability. In PT-symmetric antiferromagnetic insulators, it gives rise to an intrinsic Néel spin-orbit torque. Third, we systematically evaluate the second-order electrical, thermal, and thermoelectric transport coefficients in systems with time-reversal symmetry, revealing the interplay between side-jump and skew-scattering mechanisms in nonlinear responses. Finally, using trilayer graphene as an example, we present experimental observations of the nonlinear Nernst effect at zero magnetic field. Collectively, our work establishes a unified theoretical framework for understanding and engineering nonlinear transport phenomena.
报告人：张志帆（复旦大学）