Events

Recent experiments and theoretical studies suggest that electronic orders such as superconductivity or excitonic insulator phases can be realized in highly nonthermal systems. In this talk, I will discuss some examples which have been demonstrated in nonequilibrium dynamical mean field theory simulations of Hubbard-type models. After briefly reviewing results for nonthermal magnetic order and the eta-pairing state in photo-doped Mott insulators, I will discuss in more detail two recent studie...

The possibility to form excitons in photo-illuminated correlated materials is central from fundamental and application oriented perspectives. We show how the interplay of electron-electron interactions and a magnetic superstructure leads to the formation of a peculiar spinful exciton, which can be detected in ARPES-type experiments and optical measurements. We study this by using matrix product states (MPS) to compute the time e...

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Wide-band-gap insulators such as NiO offer the exciting prospect of coherently manipulating electronic correlations with strong optical fields . Contrary to metals where rapid dephasing of optical excitations via electronic processes occurs, the sub-gap excitation in charge-transfer insulators has been shown to couple to low-energy bosonic, probably phonon, excitations . Here we use the prototypical charge-transfer insulator NiO to demonstrate that sub-gap excitation leads to a renormalized N...

Results will be presented of how the spins, the orbitals and the lattice react to phase stable excitations of low energy phonons, electromagnons or orbitals. Examples will cover soft mode driving of the ferroelectric mode in SrTiO3, electromagnon excitation in hexaferrites and orbital excitation in magnetically frustrated Tb2Ti2O7. These ultrafast changes caused by the excitations are probed by resonant and non-resonant X-ray diffraction to obtain the lattice the spin and/or the orbital dyna...

α-GeTe(111) is a bulk ferroelectric Rashba semiconductor which exhibits the largest known Rashba-type spin splitting of so-far known materials, one of the most promising mechanism to reversibly manipulate spin polarization. Its electronic structure in the occupied states has been intensively studied by Angle Resolved Photoemission Spectroscopy (ARPES) and Spin ARPES (SARPES) , the key technique to understand the spin texture of materials. Using operando SARPES, it has been demonstrated that ...

Charge excitations across electronic band gaps are a key ingredient for transport in optoelectronics and light-harvesting applications. In contrast to conventional semiconductors, studies of above-band-gap photo-excitations in correlated materials are still in their infancy. The new idea presented in this talk is that lifetime changes after a photo-excitation in correlated systems carry essential information about the competition between active degrees of freedom. We will exemplify the concep...

Intermediate-scale quantum technologies provide unprecedented opportunities for scientific discoveries while posing the challenge of identifying important problems that can take advantage of them through algorithmic innovations. A major open problem in quantum many-body physics is the table-top generation and detection of emergent excitations analogous to gravitons -- the elusive mediators of gravitational force in a quantum theory of gravity. In solid state materials, fractional quantum Ha...

The ordering of systems emerging through non-equilibrium symmetry breaking transitions is inevitably accompanied by domain formation. The underlying microscopic physics that defines the system's energy landscape for tunneling between domain configurations is of interest in many different areas of physics, ranging from cosmology to solid state quantum matter . Domains may reconfigure by thermally-driven microscopic processes , or - in quantum systems - by macroscopic quantum tunneling. Here, w...

We investigate the quench and real-time formation of the Mott state and photoexcited carrier relaxation dynamics in the Mott insulator κ-(BEDT-TTF)2CuCl (κ-Cl) and the superconductor κ-(BEDT-TTF)2CuBr (κ-Br) using three-pulse femtosecond optical spectroscopy. In both salts, we find that transient reflectivity amplitude recovers on 2 ps timescale after a strong near-infrared pulse quench. The transient reflectivity relaxation time is nearly constant throughout indicating that the energy g...

Quantum material systems upon applying ultrashort laser pulses provide a rich platform to access excited material phases and their transformations that are not entirely like their equilibrium counterparts. The addressability and potential controls of metastable or long- trapped out-of-equilibrium phases have motivated interests both for the purposes of understanding the nonequilibrium physics and advancing the quantum technologies. Thus far, the dynamical spectroscopic probes eminently focus ...

Resistance switching between charge ordered phases of the 1T-TaS₂ has shown to be potentially useful for the development of high-speed, energy efficient non-volatile memory devices. While ultrafast switching was previously reported with optical pulses, determination of the intrinsic speed limits of actual devices that are triggered by electrical pulses is technically challenging and hitherto still largely unexplored.
Using an optoelectronic “laboratory-on-a-chip” especially design...

Tunnelling is one of the most fascinating phenomena in quantum physics, whose implications on the dynamics of many-body systems are still unclear. Recently, it has been argued that the presence of inter-particle interactions may lead to cooperative effects, such as the modification of the single-particle tunnelling between wells or the simultaneous tunnelling of a few particles as a single object through a potential barrier. Under certain conditions, these non-standard Hubbard terms are consi...