“Anomalous non-equilibrium response in black phosphorus to sub-gap mid-infrared excitation”


The electronic properties of low-dimensional semiconductors are dictated by strongly bound electron-hole pairs, which are instrumental for applications in optoelectronics and photocatalytic solar energy conversion. However, when the thickness of the material is increased to a finite size, the electron-hole Coulomb attraction is overcome by the enhanced dielectric screening of electrons, now free to re-arrange without any phase space restriction.
A team of scientists from Trieste and Modena, led by Professor Daniele Fausti (Università degli Studi di Trieste and Elettra Sincrotrone Trieste S.C.p.A.), has discovered that the interaction with suitable ultrashort pulses can change this picture. The experiment conducted by the scientists on a bulk black phosphorus sample revealed that photo-excitation with sub-gap mid-infrared light pulses inhibits the effectiveness of screening, inducing a behaviour that is mostly two-dimensional. The measurements carried out at the Q4Q labs in Elettra Sincrotrone indicated that, upon the photo-excitation, an electron-hole resonance is formed on the sub-picosecond timescale.
This is the first evidence that it may be possible to control the dimensionality of the response function in bulk black phosphorus, paving the way to the engineering of versatile van der Waals materials.

The research has been published in the journal Nature Communications (doi.org/10.1038/s41467-022-30341-4)
Last Updated on Tuesday, 20 June 2023 16:21