Projektbeschreibung
Steuerung der elektronischen Eigenschaften von Feststoffen mittels Licht könnte zu neuartigen optoelektronischen Geräten führen
Feststoffe können auf der Grundlage ihrer Leitfähigkeit (oder ihres Widerstands) und ihrer Energiebänder als Metalle, Halbleiter oder Isolierstoffe eingestuft werden. Die Energie von Elektronen in isolierten Atomen unterscheidet sich von der in Feststoffen, in denen Elektronen benachbarter Atome sehr nah aneinander geraten und sich manchmal sogar überlappen. Während Elektronen in freien Atomen diskrete Energieniveaus haben, bilden ihre verfügbaren Energiezustände in Feststoffen sogenannte „Energiebänder“. Isolierstoffe zeichnen sich durch eine große Lücke zwischen dem Energieband stabilerer Elektronen und dem „erregbarerer“ Elektronen aus, wohingegen Metalle durch überlappende Bänder gekennzeichnet sind. Das EU-finanzierte Projekt DANCE untersucht neuartige optische Verfahren zur Steuerung der Energiebänder von Feststoffen und öffnet so die Tür zu neuen optoelektronischen Geräten und Anwendungen.
Ziel
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.
Wissenschaftliches Gebiet
Programm/Programme
Thema/Themen
Finanzierungsplan
ERC-STG - Starting GrantGastgebende Einrichtung
93053 Regensburg
Deutschland