Daniel Werner
We present a solver for correlated impurity problems out of equilibrium based on a combination of the so-called auxiliary master equation approach (AMEA) and the configuration interaction expansion. Within AMEA one maps the original impurity model onto an auxiliary open quantum system with a restricted number of bath sites which can be addressed by numerical many-body approaches such as Lanczos/Arnoldi exact diagonalization (ED) or matrix product states (MPS). While the mapping becomes exponentially more accurate with increasing number of bath sites, ED implementations are severely limited due to the fast increase of the Hilbert space dimension for open systems, and the MPS solver typically requires rather long runtimes. Here, we propose to adopt a configuration interaction approach augmented by active space extension to solve numerically the correlated auxiliary open quantum system. This allows access to a larger number of bath sites at lower computational costs than for plain ED. We benchmark the approach with numerical renormalization group results in equilibrium and with MPS out of equilibrium. In particular, we evaluate the current, the conductance as well as the Kondo peak and its splitting as a function of increasing bias voltage below the Kondo temperature TK. We obtain a rather accurate scaling of the conductance as a function of the bias voltage and temperature rescaled by TK for moderate to strong interactions in a wide range of parameters. The approach combines the fast runtime of ED with an accuracy close to the one achieved by MPS making it an attractive solver for nonequilibrium dynamical mean field theory.
Andreas Krenn
Our Sun has 8 planets orbiting it. However, our Solar system is by far not unique in the universe. Many stars have planetary companions. These planets orbiting stars different to our sun are called extrasolar planets (or short: exoplanets). Since the first ever detection of an exoplanet in 1992, more than 5300 exoplanets have been confirmed. As exoplanet science progressed since the early 90s the focus shifted from only detecting the planetary signals to actually being able to characterise these distant worlds. The Characterising Exoplanet Satellite (CHEOPS), launched in 2019 and operated by the European Space Agency (ESA), uses the fact that some of these exoplanets pass in front of their star and block some of the emitted light (transit), to determine certain properties like the planetary radius and reflective characteristics of the planetary atmosphere. This presentation will give a general overview of exoplanet science and will introduce the CHEOPS mission and the extraordinary science it produces. It will especially focus on some recently published observations, which were led by scientists at the Space Research Institute of the Austrian Academy of Science as part of the CHEOPS Science Team.
Zhenhao Wang
The selection rules are significantly relaxed when molecules interact with an intense laser field in the tunneling regime, primarily due to the distorted Coulomb potential of the nuclei. Field-induced rotation, vibronic excitation, and ionization prepare both the nuclear wavepacket and the electronic wavepacket in neutral molecules and/or molecular ions, spanning a broad range of energy. As the intense laser pulse leaves the molecule, these wavepackets evolve under a field-free Coulomb potential, containing rich structural and dynamic information about the molecule and/or molecular ions. The real-time evolution of these wavepackets is monitored by another intense laser pulse, which induces dissociation and ionization. The yield of fragments and molecular ions is recorded at various time delays between the two laser pulses. The amplitude and phase of these wavepackets are imprinted in the ion yield and can be decoded through time-frequency analysis.
Ann Maria James
Organic semiconductors (OSCs) offer distinct advantages over inorganic counterparts for thin-film transistor applications. Among them, benzothieno[3,2-b]benzothiophene (BTBT) core-based small molecules are promising as p-type semiconductors. This study investigated the crystal structure, film-forming properties, and polymorphism of OEG BTBT (FD44), a BTBT derivative. High-quality single crystals of FD44 were grown on a Si substrate, revealing a monoclinic phase with a packing arrangement favoring charge transport. We also examined thin film formation through solution processing and physical vapor deposition, achieving mobilities of 6 x 10-4 cm2 V-1 s-1 on devices with physical vapor-deposited OEG-BTBT as the active channel layer. Furthermore, polymorphism studies performed on OEG-BTBT discovered three forms through classical screening and four additional forms employing the surface as a crystallization mediator. Grazing incidence X-ray diffraction (GIXD) analysis was used to collect the lattice parameter information for three-phase pure surface-exclusive polymorphs. Also, for our system of polymorphs, a fascinating memory effect was demonstrated upon recrystallizing from the melt. We conducted a comprehensive analysis using non-ambient temperature-dependent X-ray diffraction and hotstage microscopy techniques. After the analysis, we could conclude that the potentiality of recrystallizing into the same phase is limited to a particular temperature value. Moreover, we could successfully illustrate the melting point, induction time, and crystal growth kinetics associated with these new polymorphic forms. In summary, our findings shed light on the crystal structure, film properties, and polymorphism of OEG-BTBT, exploring its potential for organic electronic devices and uncovering insights into memory effects in polymorphic systems.