Optoelectronics

The creation of free electron and hole pairs may suffice to broadly explain the optical conductivity of insulators and semiconductors, but, in general, bound electron-hole pairs or excitons also play a non-negligible role. This is particularly true in two-dimensional (2D) crystals, where the excitons become tightly bound due to their confinement and low screening. These include, for instance, hexagonal boron nitride or transition metal dichalcogenides, which have been extensively studied in this regard. Additionally, it has also been shown that non-linear phenomena such as high-harmonic generation and bulk photovoltaic effects can be greatly enhanced in 2D crystals. Furthermore, the high tunability of the atomic structure through strain and the ability to select excitations based on the light polarization render 2D optoelectronics as a very active field from both fundamental and technological perspectives.

Some representative publications:

• A comprehensive study of the velocity, momentum and position matrix elements for Bloch states: Application to a local orbital basis, JJ Esteve-Paredes, JJ Palacios, SciPost Physics Core 6 (1), 002 (2022).

• Theoretical Approach for Electron Dynamics and Ultrafast Spectroscopy (EDUS), G Cistaro, M Malakhov, JJ Esteve-Paredes, AJ Uría-Álvarez, REF Silva, ... Journal of Chemical Theory and Computation (2022).

• Quenching of exciton recombination in strained two-dimensional monochalcogenides, JJ Esteve-Paredes, S Pakdel, JJ Palacios, Physical Review Letters 123 (7), 0774024 (2019).

• Strong modulation of optical properties in rippled 2D GaSe via strain engineering, D Maeso, S Pakdel, H Santos, N Agraït, JJ Palacios, E Prada, ... Nanotechnology 30 (24), 24LT01 (2019).