Conventional electrical transport measurements are intrinsically “slow” – their time resolution is limited by the bandwidths of the measurement equipment, RC constants of the circuits involved, and couplings between the wires. Now, researchers of projects B07 and B08 (leading author Denis Yagodkin, PIs Kirill Bolotin (B08) and Cornelius Gahl (B07)) have developed a new optoelectronic approach to detect electrical transport phenomena occurring at the interface between two atomically thick semiconductors with sub-picosecond time resolution [1]. The approach works by detecting changes in the current across the structure as a function of the time delay between the two femtosecond laser pulses illuminating its surface. The approach is used to detect signatures of the formation of a “dark exciton” a quasiparticle inaccessible to conventional optical techniques.

[1] D. Yagodkin, A. Kumar, E. Ankerhold, J. Richter, K. Watanabe, T. Taniguchi, C. Gahl, and K. I. Bolotin: Probing the formation of dark interlayer excitons via ultrafast photocurrent - Nano Lett. 23, 9212 (2023) - DOI: 10.1021/acs.nanolett.3c01708