**Nonreciprocal spin and charge transport in magnetic and topological materials system**

Nonreciprocal transport of spin and charge carriers may take place in materials systems that lack inversion symmetry. One prominent example is the p-n junction — the building block of various semiconductor devices (such as transistors, solar cells, LEDs, etc.) that have been an indispensable part of our daily lives. Recently, there has been a surge of interest in nonreciprocal transport effects emerging in magnetic and topological materials systems. Fundamentally, these nonreciprocal-response effects touch upon several key elements of modern condensed-matter physics, such as symmetry, band topology, and quantum interference. From a practical perspective, a fertile ground of functional materials systems can be cultivated by studying these effects.

In this talk, I will first classify nonreciprocal responses of interest based on symmetry and their nonlinear nature. I will then turn to our theoretical studies of nonreciprocal and nonlinear transport effects in magnetic and topological systems. Particular emphasis will be placed on novel nonlinear magnetoresistance effects arising from the interplay between symmetry-breaking and momentum-space chirality. The talk will conclude with an outlook on the prospects of achieving other promising nonreciprocal responses in emergent quantum materials.