Nonreciprocal electrical transport in emerging noncentrosymmetric systems: From hidden symmetry to functional devices

Contrary to the reciprocal electrical transport constrained by the Onsager relations, nonreciprocal charge transport arises in noncentrosymmetric systems where the resistance depends on the direction of current flow or external stimuli. Governed by symmetry-dependent charge dynamics, these responses appear as longitudinal nonreciprocal charge transport and the nonlinear Hall effect (NLHE) in the transverse direction. Recent theoretical advances have expanded the range of mechanisms and material platforms capable of hosting nonreciprocal signals, revealing the role of hidden band-geometric properties. In parallel, experimental developments have exploited these effects for practical devices, offering promising alternatives to semiconductor-based rectifiers and wireless components, with advantages in broadband operation, ultrafast response, and high energy efficiency. In this review, we summarize electrical measurement techniques and characteristic transport signatures for identifying nonreciprocal phenomena and uncovering their underlying symmetry. We provide a comprehensive discussion of the fundamental mechanisms underlying longitudinal nonreciprocal charge transport and NLHE, organized through representative material systems, and a subsequent examination of strategies for artificially inducing and enhancing nonreciprocity. Finally, we evaluate the technological perspectives of nonreciprocal charge transport for electronic applications, along with key challenges and opportunities for scalable device implementation. By synthesizing current progress, this review aims to guide materials discovery and device innovation, and to inspire exploration of new symmetry settings and unconventional routes toward enhanced nonreciprocal functionalities.