Project description
Controlling solids' electronic properties with light could lead to novel optoelectronic devices
Solid materials can be classified as metals, semiconductors or insulators based on their conductivity (or resistivity) and energy bands. The energy of electrons in isolated atoms is different from that in solids, where electrons of neighbouring atoms come very close and even overlap at times. Whereas electrons in free atoms have discrete energy levels, their available energy states in solids form so-called 'energy bands'. Insulators are characterised by a large gap between the energy band of more stable electrons and that of more 'excitable' ones, whereas metals are characterised by overlaps in bands. The EU-funded DANCE project is investigating novel optical methods to control the energy bands of solids, opening the door to new optoelectronic devices and applications.
Objective
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.
Fields of science
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Funding Scheme
ERC-STG - Starting GrantHost institution
93053 Regensburg
Germany