Research

Ultrafast vibrational spectroscopy

Structural dynamics, that is, the motion of atoms on their intrinsic time scales, ranging from a few to many thousands of femtoseconds (1 fs = 10^-15 s), play a crucial role in elementary processes in molecules and materials. These processes include, among others, charge transfer in light-harvesting molecular assemblies, quasiparticle dynamics, and phase transitions in quantum materials.

In our group, we develop experiments that investigate such phenomena from a lattice- and structure-centered perspective. In time-resolved impulsive stimulated Raman spectroscopy, we synthesize pairs of broadband, few-femtosecond light pulses to directly track vibrational motion in the time domain during and after photoexcitation. This approach allows us to record the vibrational structure of excited states in molecules and materials over a wide spectral range, covering low-frequency lattice modes in solids as well as the fingerprint region of functional molecules.

By capturing structural information of systems in action, our work provides key insights that support molecular synthesis, materials design, and the optical control of matter far from equilibrium.

 

Opto-structural control of matter

A central focus of our group is the development of experimental tools that allow us to control the microscopic motion of atoms with light. By selectively driving atomic motion, we can manipulate technologically relevant properties of materials and molecules, including electrical conductivity, magnetism, ferroelectricity, topology, as well as charge transfer and chemical reactivity.

To achieve this, we generate intense, tailored light pulses in the mid-infrared regime of the electromagnetic spectrum that resonantly and nonresonantly excite lattice vibrations to large amplitudes without populating electronic states. This enables a highly selective and non-thermal route to materials control. We probe the resulting changes in physical and chemical properties using ultrafast linear and nonlinear optical spectroscopies, such as second-harmonic generation, polarization rotation, and time-resolved impulsive stimulated Raman scattering.

Our approach aims at a more energy-efficient control of material properties, and enables access to transient states of matter with functionalities that are inaccessible under thermal equilibrium conditions.