arXiv subjects

Christian Strüber

Publications and source records attributed to Christian Strüber.

3 recordsLinked to original sources

arXiv2025

Ultrafast non-equilibrium magnon generation and collapse of spin-orbit hybridization gaps in iron

We distinguish between longitudinal and transverse spin excitations in the ultrafast response of iron by probing exchange splitting {\Delta}Eex and magnetic linear dichroism (MLD) in time- and angleresolved photoemission. Comparing spin-split partner bands at the Fermi level shows that {\Delta}Eex remains constant upon optical excitation. In contrast, the different MLD response of spin-orbitsplit valence bands reveals non-equilibrium, transverse spin dynamics. Magnon generation in Fe is ultrafast, electronic band specific, and drives the collapse of spin-orbit hybridization gaps.

cond-mat.other↗

arXiv2025

Momentum transfer in the ponderomotive potential of near-infrared laser pulses leads to sizable energy shifts and electron-wavepacket squeezing in time-resolved ARPES

We observe momentum transfer in the ponderomotive potential of near-infrared (NIR) laser pulses in time- and angle-resolved photoemission spectroscopy (tr-ARPES) experiments with ultrashort extreme ultraviolet probe pulses. Acceleration of photoelectrons in the transient grating provided by an intense laser pulse reflected at a surface leads to delay-dependent oscillations of electric kinetic energies. Photon and electron momenta determine the oscillation frequency. We experimentally observe and theoretically simulate electron yield modulations driven by a novel electron-energy bunching effect. Measurement results are simulated and fitted with high accuracy. Complete reversion of the ponderomotive momentum transfer allows for retrieval of the undisturbed initial state and the transient band structure for overlapping pump and probe pulses.

cond-mat.mes-hall↗

arXiv2016

Strong-field ionization of clusters using two-cycle pulses at 1.8~$μ$m

The interaction of intense laser pulses with nano-scale particles leads to the production of high-energy electrons, ions, neutral atoms, neutrons and photons. Up to now, investigations have focused on near-infrared to X-ray laser pulses consisting of many optical cycles. Here we study strong-field ionization of rare-gas clusters ($10^3$ to $10^5$ atoms) using two-cycle 1.8~$μ$m laser pulses to access a new interaction regime in the limit where the electron dynamics are dominated by the laser field and the cluster atoms do not have time to move significantly. The emission of fast electrons with kinetic energies exceeding 3keV is observed using laser pulses with a wavelength of 1.8~$μ$m and an intensity of $1\times 10^{15}$~W/cm$^2$, whereas only electrons below 500eV are observed at 800nm using a similar intensity and pulse duration. Fast electrons are preferentially emitted along the laser polarization direction, showing that they are driven out from the cluster by the laser field. In addition to direct electron emission, an electron rescattering plateau is observed. Scaling to even longer wavelengths is expected to result in a highly directional current of energetic electrons on a few-femtosecond timescale.

physics.atm-clus↗