Mobile excitons as neutral information carriers

Excited about excitons? You should be. As charge neutral and thus efficient data transmitters, these quasiparticles could revolutionise electronics – but only if they can move. Now, for the first time, an international collaboration led by PSI have created and detected dispersing excitons in a metal using angle-resolved photoemission spectroscopy. They publish their observations in the journal Nature Materials.

Excitons are temporary bound states between electrons and positively charged holes, created when an electron absorbs a photon and moves to an excited state, leaving behind a hole in the valence band. Mobile excitons, due to their charge neutrality, offer great promise as a means for transmitting information without losses resulting from interactions with other charges en route. In contrast, the numerous interactions of electrons lead to resistance, heating and limitations in computational efficiency. Yet, the phenomenon of mobile excitons in metals has until now remained elusive, with traditional optical experiments only creating and detecting excitons with negligible momentum.  Now, researchers at the Swiss Light Source have observed dispersing excitons with large momentum for the first time in the transition metal trichalcogenide, TaSe3.

Read more on the PSI website

Image: Using ARPES, researchers could create and observe excitons diffusing along the chains of the quasi-1D metal, TaSe3. These mobile excitons come with various internal structures: interchain (red light), intrachain (pink light), or trions, formed from two electrons and a hole (blue light)

Credit: Junzhang Ma