Researchers Jun-Xiao Hui and Qing-Dong Jiang from the University of Hong Kong have proposed a novel theoretical approach to identify and control exciton superfluidity in solid-state platforms. Their work focuses on a phenomenon known as nonreciprocal perfect Coulomb drag, which could have significant implications for the energy sector, particularly in the development of advanced electronic and optoelectronic devices.
Excitons are bound pairs of electrons and holes that can form in semiconductors when light is absorbed. In certain conditions, these excitons can condense into a state known as an exciton condensate, which exhibits macroscopic phase coherence. This state is distinct from an excitonic gas or insulator, which also features bound electron-hole pairs but lacks this coherence. The challenge lies in distinguishing between these states and identifying the unique properties of an exciton condensate.
Hui and Jiang propose that a spin-orbit-coupled bilayer system can host a finite-momentum exciton condensate. This condensate exhibits a nonreciprocal perfect Coulomb drag, a phenomenon where the drag resistance depends on the direction of the current. This effect arises from the breaking of inversion and time-reversal symmetries in the exciton condensate, resulting in direction-dependent critical counterflow currents.
The nonreciprocal perfect Coulomb drag provides a clear and unambiguous transport signature of phase-coherent exciton condensation. This means that it offers a powerful and experimentally accessible approach to identify, probe, and control exciton superfluidity. The ability to control exciton superfluidity could lead to the development of novel electronic and optoelectronic devices, such as excitonic transistors and diodes, which could be more efficient and versatile than current technologies.
The research was published in the journal Physical Review Letters, a prestigious journal in the field of physics. While the work is theoretical, it provides a clear path forward for experimentalists to test these predictions and potentially unlock new technologies for the energy sector. The proposed coherent-exciton diode effect could have practical applications in the development of advanced energy conversion and storage devices, as well as in the field of quantum computing.
This article is based on research available at arXiv.