Charge-density waves (CDWs) represent a model system for broken-symmetry states arising from the strong interplay of the charge and lattice degrees of freedom. Manipulation of such collective states promises microscopic insight into the fundamental interactions underlying the transition, and novel opportunities for applications. Time- and angle-resolved photoemission spectroscopy (trARPES) as...
The material 1T-IrTe2 is a transition-metal dichalcogenide with a substantial coupling across the planes. Upon cooling, it undergoes a first-order phase transition at about 278 K from a 1 × 1 × 1 phase into a 5 × 1 × 5 phase. Here, we present a time-resolved x-ray photoemission spectroscopy (tr-XPS) and a time-resolved angle resolved photoemission spectroscopy (tr-ARPES) studies using the...
Due to its topological properties, skyrmions offer appealing interest in both fundamental and in spintronic applications. Here, we show combining a femtosecond laser and real space imaging technique in a cryo-Lorentz Transmission Electron Microscope that we can rotate the skyrmion lattice by a discrete amount in a coherent and fully deterministic manner. Using circular polarized pulses in a...
Local excitations in magnetic materials are usually highly incoherent, since they dephase quickly due to mutual interactions. However, there are interesting exceptions to this common lore.
Our study of the random rare-earth magnet LiY$_{1−x}$Tb$_x$F$_4$ reveals that a combination of hyperfine interactions, external magnetic fields and disorder allows certain excitations on pairs of Tb sites...
We report how a new type of chiral superconducting phase can be stabilized in photodoped frustrated Mott insulators. The metastable phase features a spatially varying order parameter with a 120 degree phase twist which breaks both time-reversal and inversion symmetry. Under an external electric pulse, the 120 degree chiral superconducting state can exhibit a second-order supercurrent...
Systems with spin orbit coupling (SOC) driven out of equilibrium give rise to interesting electron dynamics due to their coupling between the electron spin and momentum. Recent efforts have been made in order to understand the imprints of SOC on the high harmonic generation spectra of solids. In a parallel development, the field of non-equilibrium superconductivity in unconventional...
Mott insulators are archetypal examples of quantum materials. Some Mott insulators exhibit an drop in resistivity under the application of electric fields with durations of ~10 microseconds, with typical threshold fields of a few kV/cm. These electrical Mott transitions are volatile for fields just above threshold but become persistent for higher fields.
Electric fields of 1 MV/cm can be...
Time-resolved spectroscopies have provided various insights in the quest for understanding the fundamental properties of quantum materials and towards controlling their functional properties through light-matter interaction. In this regard, Free Electrons Lasers (FEL) have developed as a powerful tool to perform ultrafast X-ray spectroscopy allowing to obtain time-, energy- and...
Magnetic switching by light remains little understood even after decades of study. Here we present a previously unexplored switching mechanism using X-rays on multiferroic (Ge,Mn)Te. It will be shown that the ferrimagnetic system can be reliably switched using stochastic resonance in XMCD and that the switching mechanism can be stopped by changing one of the two input frequencies. The observed...
We highlight the current-induced modification of magnetism in the prototypical 5d Mott insulator Sr2IrO4 whose moments are entangled combinations of spins and orbitals. Based on an earlier report, oxygen octahedra can be rotated by applying electric current. Using muon spin spectroscopy, we further resolved an uncharted rotation of the magnetic moments. Such change is likely beyond the locking...
The layered transition metal dichalcogenide 1$T$-TaS$_2$ has been studied intensively due to the interplay between structural transitions and the associated electronic phases. In the low temperature regime the monolayer behaves as a Mott insulator, while, when the bulk is considered, the electronic state is influenced by the presence of a strong bilayer hybridization favouring a band insulator...
Calculating the single-particle and two-particle correlations of interacting lattice systems in a consistent and con- serving manner is a challenging task. Nonlocal correlations play an important role in low-dimensional systems and in the vicinity of phase transitions and crossovers. We establish, use and implement the non-equilibrium framework of two methods that deal self-consistently with...
Transient grating (TG) is widely used in the optical domain to gain information on transport-diffusion processes and on vibrational, charge and magnetic dynamics of the ground and excited state. Extension of TG to X-rays would allow to overcome the limitations of the longer wavelengths reaching the ultimate time and spatial resolutions (femtosecond/sub-nanometer) with high momentum-transfer,...
