Thema: 
Challenges and solutions for electron microscopy and spectroscopy in the field of chemical energy conversion 
Datum: 
30.05.22 
Uhrzeit: 
16:15 
Ort: 
H6 & online 
Vortragender: 

MPI für Chemische Energiekonversion, Mülheim a.d.R 

Inhalt: 
Analytical transmission electron microscopy (TEM) has become a widely implemented technique in a modern research institute involved in catalysis and materials science which are key topics in the field of chemical energy conversion. To get the full picture when investigating different materials and their properties, several analytical techniques available in TEM have to be combined and compared with the results of other analytical instruments. However, usually TEM specialists perform the necessary tasks for a thorough microscopical study of the materials of interest. The need for generating standard procedures and workflows optimized for nonexpert TEM users has been addressed in our ChemiTEM project. The developed workflows were implemented into a tablet app enabling nonexpert TEM users to perform even applications they have no previous experience with by guiding them through all necessary decision processes. The app also includes a workflow for data analysis. All this renders the set of standardized workflows a versatile toolbox for TEM applications in material synthesis and chemistry. In many cases, samples have to be investigated under inert conditions, e.g., when catalysts consist of reduced metals. We developed a new method to perform such investigations without the necessity to use dedicated sample holders but instead being able to harness the capabilities of standard sample holders. I will present some examples of the interplay of different analytical techniques as well as results of the ChemiTEM project and our inert investigation techniques. In addition, a short outlook on the development of standardized workflows for electron energyloss spectrometry (EELS) and Xray photoelectron spectroscopy (XPS) will be given. 
Ansprechpartner: 
Thema: 
tba 
Datum: 
03.06.22 
Uhrzeit: 
16:15 
Ort: 
V4119 
Vortragender: 

University of Hamburg 

Inhalt: 

Ansprechpartner: 
Thema: 
tba 
Datum: 
30.06.22 
Uhrzeit: 
14:15 
Ort: 
D6135 
Vortragender: 

Universität Bern 

Inhalt: 

Ansprechpartner: 
Thema: 
14.00 Probing and utilizing spinelectric couplings in molecular magnets 
Datum: 
03.06.22 
Uhrzeit: 
14:00 
Ort: 
ZOOM / Konferenzschaltung 
Vortragender: 
Jakub Mrozek 
University of Oxford, now Helsinki 

Inhalt: 
Molecular magnets have been demonstrated as promising candidates for quantumcoherent nanodevices, due to their long relaxation times and design flexibility. They are most typically investigated and operated using Electron Paramagnetic Resonance. However, relying only on the intrinsic coupling between their spins and the magnetic field while building quantum presents a challenge, as magnetic fields, unlike electric fields, are not easily constrained to required length scales. Using modified Hahn echo microwave pulse sequences incorporating static electric fields, we investigated electric field sensitivity and its origins in several molecular magnets, such as Cu3 frustrated triangles[1], Cr7Mn rings [1], and HoW10 crystals[2][3], aiming to find the key to the design of a magnetic molecule that may be operated with electrical means. We discover couplings sufficient to use an electric field to address subpopulations of molecular spins by modifying their operating frequencies and demonstrate such selection experimentally. [1] J. Liu, J. Mrozek et al., Phys. Rev. Lett 2019, 122, 037202 [2] J. Liu, J. Mrozek et al., Nature Physics 2021, 17, 1205–1209 [3] M. Shiddiq et al., Nature 2016 531, 348–351 
Ansprechpartner: 
Thema: 
Manyparticles diffusing with resetting: study of the largedeviation properties of the flux distribution 
Datum: 
05.05.22 
Uhrzeit: 
16:00 
Ort: 
D5153 
Vortragender: 
Costantino Di Bello 
Inhalt: 
In this paper we studied a model of noninteracting particles moving on a line following a common dynamics. In particular we considered either a diffusive motion with Poissonian resetting, and a runandtumble motion with Poissonian resetting. We were interested in studying the distribution of the random variable $Q_t$ defined as the flux of particles through origin up to time $t$. We used the notation $P(Q,t)$ to identify the probability $\mathbb{P}\{Q_t=Q\}$. We considered particles initially located on the negative half line with a fixed density $\rho$. In fully analogy with disordered systems, we studied both the annealed and the quenched case for initial conditions. In the former case we found that, independently from the specific dynamics, $P_\mathrm{an}(Q,t)$ has a Poissonian shape; while in the latter case, for what concerns the diffusive dynamics with resetting, the large deviation form of the quenched distribution reads $P_\mathrm{qu}(Q,t)\sim \exp\left[r^2t^2 \Psi_\mathrm{diff}\left(\dfrac{Q}{\rho t}\right)\right]$ with the large deviation function $\Psi_\mathrm{diff}(x)$ exhibiting a discontinuity in the third derivative, hence aiming, despite the simplicity of the model, at the exhistence of a dynamical phase transition. The quenched distribution for the runandtumble dynamics, instead, does not exhibit any kind of phase transition. Importance sampling Monte Carlo simulations were performed to prove the analytical results. References: Current fluctuations in noninteracting runandtumble particles in one dimension Tirthankar Banerjee, Satya N. Majumdar, Alberto Rosso, and Grégory Schehr, Phys. Rev. E 101, 052101 https://doi.org/10.1103/PhysRevE.101.052101 Current Fluctuations in One Dimensional Diffusive Systems with a Step Initial Density Profile B. Derrida and A. Gerschenfeld, J. Stat. Phys. 137, 978 (2009) https://doi.org/10.1007/s1095500998301 
Ansprechpartner: 
Thema: 
tba 
Datum: 
01.06.22 
Uhrzeit: 
09:00 
Ort: 
ZOOM / Konferenzschaltung 
Vortragender: 

Université Paris Dauphine 

Inhalt: 
tba 
Ansprechpartner: 