Coherence and dynamics of single semiconductor nanowires with attosecond pulses

Semiconductor nanowires are a promising class of photovoltaic materials with properties that differ from bulk material.

Due to their small size, acoustic phonons are confined in the low dimensional structure giving unique properties, such as strong light-matter coupling.

This proposal aims to study ultrafast dynamics and coherence in semiconductor single nanowires using Attosecond Transient Absorption Spectroscopy, (ATAS) and time-resolved Photoemission Electron Microscopy (TR-PEEM).

In ATAS, by implementing nanofocusing of the attosecond probe, hot carrier-coherent phonon dynamics and exciton coherence can be studied for different nanowire geometries.

The PEEM measurements allows access to local changes in the optical field, hot electron dynamics and charge transport in the surface region.

The project is divided into two parts, where the first two years are conducted at UC Berkeley, under supervision of Prof. Stephen R. Leone. In Berkeley, ATAS measurements on single nanowires will be performed. The final year is spent at Lund University under supervision of Prof. Anders Mikkelsen, where TR-PEEM measurements will be conducted on similar samples as the ones studied in Berkeley.

If hot carrier cooling is well understood, given a specific material and wire geometry, it could pave the way for new photovoltaic platforms.

Additionally, the characterization of excitonic coherence in these materials could give better understanding of their underlying principles and performance.