Descrizione del progetto
Il controllo delle proprietà elettroniche dei solidi con la luce potrebbe portare a nuovi dispositivi optoelettronici
I materiali solidi possono essere classificati come metalli, semiconduttori o isolanti in base alla loro conducibilità (o resistività) e alle bande di energia. L’energia degli elettroni negli atomi isolati è diversa da quella dei solidi, dove gli elettroni degli atomi vicini si avvicinano molto e a volte si sovrappongono. Mentre gli elettroni negli atomi liberi hanno livelli di energia discreti, i loro stati energetici disponibili nei solidi formano le cosiddette «bande di energia». Gli isolanti sono caratterizzati da un ampio divario tra la banda di energia degli elettroni più stabili e quella degli elettroni più «eccitabili», mentre i metalli sono caratterizzati da sovrapposizioni di bande. Il progetto DANCE, finanziato dall’UE, sta studiando nuovi metodi ottici per controllare le bande di energia dei solidi, aprendo la strada a nuove applicazioni e dispositivi optoelettronici.
Obiettivo
The band structure of solids is mainly determined by the orbital overlap between neighboring atoms. Therefore, electronic properties are commonly controlled via the chemical composition that determines the relevant structural parameters such as bond angles and lengths. DANCE will use a radically different approach where control of the effective orbital overlap is achieved by periodic modulation of the solid with strong mid-infrared and terahertz light fields. In this way, DANCE will control the band structure including topology, many-body-interactions, and spin. The induced band structure changes will be investigated with time- and angle-resolved photoemission spectroscopy.
I will implement two different driving schemes that either coherently modulate the atomic positions or the momentum of the Bloch electrons. Resonant excitation of infrared-active phonon modes results in a periodic modulation of the band structure at twice the driving frequency and, thus, a modified average band structure. In addition, non-linear coupling to Raman-active phonons leads to new quasi-static crystal and band structures. Coherent modulation of the Bloch electron’s momentum becomes possible if the scattering time is bigger than the inverse driving frequency and is predicted to result in various topological phase transitions as well as dynamical localization of carriers. I will apply this approach to different low-dimensional solids with strong electron-phonon coupling and Dirac materials with long scattering times.
DANCE will address the following key questions: Can we switch between metallic, insulating and topological phases? Can we shape the potential energy surface of the solid to stabilize symmetry-broken ground states? Can we generate artificial magnetic fields to control the electron spin? The success of DANCE will establish dynamical band structure engineering as a new method for electronic structure control and pave the way for novel optoelectronic and optospintronic devices.
Campo scientifico
Programma(i)
Argomento(i)
Meccanismo di finanziamento
ERC-STG - Starting GrantIstituzione ospitante
93053 Regensburg
Germania