IMPRS Workshop 2018: From Models to Reality

19 Feb 2018, 00:30 → 23 Feb 2018, 18:00 Europe/Berlin

Schloss Ringberg am Tegernsee

Welcome to the website of the International Max Planck Research School "Functional Interfaces in Physics and Chemistry" (IMPRS) workshop 2018.

The workshop will take place at Ringberg Castle close to Tegernsee in the Bavarian Alps February 19 - 23, 2018.
It is fully organized by the IMPRS students from the Fritz-Haber-Institute der Max-Plank-Gesellschaft, Freie Universität Berlin, Technische Universität Berlin, Humboldt-Universität zu Berlin and Universität Potsdam.

The topic of this workshop is Leaving the Ivory Tower: From Models to Reality. A wide range of topics will be covered, ranging from the microscopic level (electronic structure, reaction mechanisms, ...) to macroscopic applications (catalysts, functional materials, engineering applications).

The Book of Abstract is now available here.

 

Monday, 19 February

Historical Tour

18:30 Dinner

Icebreaker Session

Tuesday, 20 February

08:00 Breakfast

08:50 Welcome

1. Tuesday Morning

1 Chemical Modification of 2D Materials

Understanding the chemical reactivity of 2D materials such as graphene and hexagonal-boron nitride (h-BN) is of fundamental importance for obtaining flexible and tunable materials for devices and electronic applications, as well as for fundamental science to obtain concepts for the chemistry on such materials. The interaction of graphene and h-BN with oxygen and atomic hydrogen will be discussed in details and the results for the two substrates will be compared. While in the case of atomic hydrogen, graphene forms graphone, i.e. fully hydrogenated graphene, for h-BN hydrogen can bond and intercalate, depending on the exposure. Interestingly, graphene does not react with molecular oxygen, even when supplied with a high kinetic energy of 0.7 eV, while h-BN readily forms bonds to oxygen, intercalates or even reacts, depending on the substrate temperature. Further insights to the bonding and reaction mechanisms of hydrogen and oxygen are obtained from DFT calculations.

Speaker: Christian Papp (Physikalische Chemie II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany)

2 Recent Progress in Applying Coupled Cluster Theories to Ground and Excited State Properties of Solids and Surfaces

This presentation will review recent progress in applying periodic coupled cluster theories to the study of surfaces and solids. We will briefly discuss methods that reduce the computational cost and accelerate convergence of calculated properties towards the complete basis set as well as thermodynamic limit [1-4]. These recent developments have enabled an increasing number of ab-initio studies and allowed for assessing the accuracy of coupled cluster theories by comparing to experimental findings as well as quantum Monte Carlo results. The presented applications will include phase transitions of solids [5], molecular adsorption energies [6-7], hydrogen dissociation on silicon surfaces as well as ground and excited state studies of defects in solids.

References
[1] A. Grüneis, Phys. Rev. Lett. 115 066402 (2015).
[2] G. H. Booth, T. Tsatsoulis, G.K.L. Chan, A. Grüneis, J. Chem. Phys. 145 084111 (2016).
[3] K. Liao, A. Grüneis, J. Chem. Phys. 145 141102 (2016).
[4] F. Hummel, T. Tsatsoulis, A. Grüneis, J. Chem. Phys. 146 124105 (2017).
[5] A. Grüneis, J. Chem. Phys. 143, 102817 (2015).
[6] T. Tsatsoulis, et al. , J. Chem. Phys. 146 204108 (2017).
[7] Y. S. Al-Hamdani, et al., J. Chem. Phys. 147, 044710 (2017).

Speaker: Andreas Grüneis (Vienna University of Technology, Austria)

10:40 Coffee Break

3 Charge and Spin Dynamics of Atoms on Surfaces

Spin and charge correlations are particularly pronounced in nanoscale materials and enable new technologies that harness quantum behavior. Accessing these correlations on their intrinsic length and time scales is an important step towards a microscopic understanding of correlated-electron physics.

We combine scanning tunneling microscopy with pump probe schemes [1] to achieve ultrafast spectroscopy of spin and charge dynamics with atomic spatial resolution. Using different electronic and optical techniques it is possible to achieve time resolution between milliseconds and femtoseconds thereby matching the instrument to the dynamics of the investigated system. In this talk I will review recent advances in ultrafast scanning probe microscopy and then discuss two experiments: one in which we fabricated a few-atom spin sensor that dynamically measures minute magnetic interactions with nearby magnetic atoms [2]; and one in which we observe the ultrafast motion of a two-dimensional correlated-electron state in the vicinity of defects.

These experiments shed light onto the impact of correlations and coherences in quantum materials and highlight pathways to design and control matter at the single atom level.

References
[1] S. Loth, M. Etzkorn, C. P. Lutz, D. M. Eigler, A. J. Heinrich, Science 329, 1628 (2010).
[2] S. Yan, L. Malavolti, J. Burgess, S. Loth, Science Adv. 3 e1603137 (2017).

Speaker: Prof. Sebastian Loth (Institut für Funktionelle Materie und Quantentechnologien, Universität Stuttgart, Germany)

11:50 Group Discussion

12:30 Lunch

2. Tuesday Evening

4 Molecular Doping for Organic Semiconductors Interface Engineering: Principles and Reality

Molecular doping is key to controlling the electronic and electrical properties of organic semiconductors, lower contact resistance, enhance bulk conductivity and carrier mobility, and create higher performance devices. This talk reviews processes and options for interface doping in molecular and polymer semiconductors, and the roles that electron spectroscopy and carrier transport measurements have played in defining key issues. Various n- and p-type molecular dopants, their doping strength and the challenges they pose are reviewed first. Specific examples will be reviewed. First is the surface/interface doping of polymer-based devices via soft-contact lamination of highly doped interlayers [1,2]. We look at the electrical characteristics of the laminated polymer/polymer interface (with P3HT, PBDTTT-c or poly-TPD), at the problem of dopant diffusion across boundaries, and at the performance of polymer-based solar cells built with laminated hole-extraction layers [3]. We then turn to the issue of improving contacts to very low electron affinity (EA) electron transport layers (ETL), an issue critical to green and blue OLEDs. We look at the air-stable dimer of (pentamethylcyclopentadienyl)(1,3,5-trimethylbenzene)ruthenium ([RuCp*Mes]2) [4], and use it to n-dope phenyldi(pyren-2-yl)phosphine oxide (POPy2) (EA = 2.1 eV). We demonstrate that photo-activation of the cleavable dimeric dopant results in kinetically stable and efficient n-doping of the host semiconductor, whose reduction potential is beyond the thermodynamic reach of the dimer’s effective reducing strength [5]. We demonstrate the use of this doped ETL to fabricate high-efficiency organic light-emitting diodes. If time permit, surface n-doping of graphene to decrease its work function, shift its Fermi level and improve electron injection in organic ETLs will be described.

References
[1] A. Shu, A. Dai, H. Wang, Y.-L. Loo, and A. Kahn, Org. Electr. 14, 149 (2013).
[2] A. Dai, A. Shu, H. Wang, S. Barlow, S. Mohapatra, T. Sajoto, Y. Zhou, C. Fuentes-Hernandez, Y.-L. Loo, S. R. Marder, B. Kippelen, and A. Kahn, Adv. Funct. Mat. 24, 2197 (2014).
[3] A. Dai, A. Wan, C. Magee, Y. Zhang, S. Barlow, S. R. Marder and A. Kahn, Org. Electr. 23, 151 (2015)
[4] G. Song, S.-B. Kim, S. Mohapatra, Y. Qi, T. Sajoto, A. Kahn, S. R. Marder, S. Barlow, Adv. Mat. 24, 699 (2012).
[5] X. Lin, B. Wegner, K. M. Lee, M. Fusella, F. Zhang, K. Moudgil, B. Rand, S. Barlow, S. R. Marder, N. Koch and A. Kahn, Nature Materials (2017) DOI: 10.1038/nmat5027.

Speaker: Antoine Kahn (Princeton University, USA)

5 Magnetocrystalline Anisotropy in Monolayer Systems: Transition-Metal-Organic Coordination Networks and Lanthanide-Metal Alloys

Various interactions contribute to the existence of an easy magnetization axis or plane in a system, a phenomenon known as magnetic anisotropy. Among those contributions, the so-called magnetocrystalline anisotropy (MCA) is fundamental to understand magnetism at the nanoscale, since it is intimately related to the electronic structure. MCA is due to the spin-orbit (SO) interaction and it is enhanced by reduced dimensionality. Thus, giant MCA is commonplace for single adatoms or molecules and bidimensional magnetic systems.

Since the energies associated to MCA are small (often well below the meV), perturbative models have been used to describe it [1], such as spin effective hamiltonians for isolated magnetic moments. However, these models present limitations when the ion hybridizes strongly with its surroundings. Alternatively, DFT calculations including SO terms offer a reliable description in those cases, although they might be sometimes impractical due to the accuracy needed to account for the small MCA energies.

We will discuss free-standing transition-metal-organic coordination networks. Although SO effects may seem small a priori here, this example nicely illustrates the complexity behind an easy magnetization axis or plane. For model Mn- and Ni-TCNQ rectangular lattices [2] we have found, using DFT calculations, how to tune the MCA upon alteration of the electronic structure by charge transfer from the substrate, lattice strain, or by symmetry breaking. Due to the latter effect in Ni-TCNQ, strong azimuthal anisotropy energy differences of up to 1.5 meV (measured with the OZ easy axis reference) are obtained.

The second example is the GdAu$_2$ monolayer alloy, studied both experimentally (XMCD, MOKE, and ARPES) and theoretically (DFT). In this strong SO-coupled system we have found in-plane MCA, as opposed to pure Gd surfaces, characterised by perpendicular anisotropy. Our result is a consequence of the formation of Gd(d)-Au(s) hybrid bands [3]. Further, when GdAu$_2$ is used as a substrate it induces a magnetization direction change in deposited Co [4].

References
[1] G. van der Laan, J. Phys.: Condens. Matter 10, 3239 (1998).
[2] M.N. Faraggi et al, J. Phys. Chem. C 119, 574 (2015).
[3] M. Ormaza et al. Nano Lett. 16, 4230-4235 (2016).
[4] L. Fernández et al., Nano Lett. 14, 2977-2981 (2014).

Speaker: Dr Maria Blanco-Rey (Departamento de Física de Materiales, Universdad del País Vasco UPV/EHU, Spain)

15:40 Coffee Break

6 Surface-Enhanced Raman Spectroscopy of Molecular Electronic Junctions

Metal-molecule-metal junctions are attractive for many applications such as energy harvesting and sensing and a wide variety of techniques have been developed for their creation and electrical characterization.
In particular vibrational spectroscopy of metal-molecule-metal junctions is desirable simply because it shows whether the molecule remains intact and whether any new vibrational modes in the spectrum indicate actual bond formation between a functional group and a metal layer. Moreover, in the context of molecular electronics, it permits detecting the effect of an applied electric field on the molecular structure or any coupling between electronic transport in the junction and vibrational modes.
Vibrational spectroscpy is however much less advanced due to the combined challenges of detecting a small signal whilst forming an intact sandwich system. In this talk I will show that even nonideal surfaces such as roughened gold or gold nanopartcles can be used to detect partial layer metallization by Surface-enhanced Raman spectroscopy (SERS) for the example of 4-mercaptopyridine, 4-4'-bipyridine and pyridyl-dithiocarbamates. I will also address to which degree SERS can be used to detect adsorbate charge transfer resonances, in particular on nonideal surfaces.
In the final part of the talk I will give an example of how to generate impact from even very fundamental research and explain what links rose petals, thread seal tape and CF16 gaskets.

Speaker: Dr Heike Arnolds (Department of Chemistry, University of Liverpool, UK)

16:50 Group Discussion

18:30 Dinner

7. Poster Session I

Poster Session I

Wednesday, 21 February

08:00 Breakfast

3. Wednesday Morning

7 Electrifying Model Catalysis: Out of the Vacuum - Into the Electrolyte

Electrocatalysis is the key to our future transition to a renewable energy system. Yet, our fundamental understanding of electrocatalysis lags behind classical heterogeneous catalysis, which has dominated chemical technology for a long time.

Here, we describe a new strategy to advance fundamental studies on electro­catalytic materials. We propose to “electrify” complex model catalysts made by surface science methods to explore electrocatalytic reactions in liquid environments. We demonstrate the feasibility of this concept by transferring an atomically-defined platinum/cobalt oxide model catalyst into the electrochemical environment while preserving its atomic surface structure. Combining vibrational spectroscopy, ambient photoelectron spectroscopy, and other surface science and electro­chemical methods, we explore particle size effects and identify hitherto unknown metal-support interactions that stabilize oxidized platinum at the metal-support interface. The latter effect opens a new synergistic reaction pathway that involves both metallic and oxidized platinum. Our results illustrate the potential of the concept, which makes available a systematic approach to build atomically-defined model electrodes for fundamental electrocatalytic studies.

Speaker: Joerg Libuda (Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany)

8 What we do and don’t know about water at interfaces – Molecular Level Insight from Computer Simulation

There are few molecules, if any, more important than water. Yet remarkably little is known about how it interacts with solid surfaces, particularly at the all important atomic-level. This is true despite widespread general interest and compelling environmental and economic incentives. For example, water-solid interactions play a crucial role in the activity of fuel cells, the chemistry of the atmosphere, global warming, corrosion, catalysis, the operation of membranes, and so on. In this talk I will discuss some of our recent work in which we have been using classical and quantum molecular dynamics approaches as well as advanced electronic structure methods to better understand the structural and dynamical properties of water-solid interfaces. This will include work focused on understanding the formation of ice [1-3], confined water in nanocapiliaries [4], and water diffusion and friction [5-7].

References
[1] M. Fitzner, G. C. Sosso, S. J. Cox and A. Michaelides, J. Am. Chem. Soc. 137, 13658 (2015).
[2] G. Sosso et al., J. Phys. Chem. Lett. 7, 2350 (2015).
[3] A. Kiselev et al, Science (2016); DOI: 10.1126/science.aai8034.
[4] J. Chen, G. Schusteritsch, C. J. Pickard, C. G. Salzmann and A. Michaelides, Phys. Rev. Lett. 116, 025501 (2016).
[5] G. Tocci, L. Joly and A. Michaelides, Nano Lett. 14, 6872 (2014).
[6] M. Ma, G. Tocci, A. Michaelides and G. Aeppli, Nature Materials 15, 66 (2016).
[7] L. Joly, G. Tocci, S. Merabia, and A. Michaelides, J. Phys. Chem. Lett. 7, 1381 (2016).

Speaker: Angelos Michaelides (London Centre for Nanotechnology, UK)

10:40 Coffee Break

9 Thin Oxide Film Based Model Catalysts - From UHV to Environmental Conditions

Ultrahigh vacuum-based surface science studies of model catalysts consisting of metal nanoparticles supported by thin, single-crystalline oxide films have allowed to address catalysis-related topics (metal-substrate interaction, adsorbate-substrate interaction, catalytic active sites, etc.) on a fundamental level. This talk deals with thin oxide films applied in more applied settings. They were utilized as oxide substrate for the preparation of oxide-supported metal nanoparticle model catalysts by deposition of metal salts from aqueous solutions (Surface Science approach to catalyst preparation), and in electrochemical studies. I will present the results of combined STM and XPS studies of the preparation of oxide-supported Pd and Au nanoparticles, and in particular report on the influence of preparation parameters (e.g. solution pH, water rinsing, chloride effect) on the morphology of the model catalyst. Results about the stability of oxide films in electrolyte solutions and under applied potential, and the influence of an organic adsorbate (catechol) on the solubility will finally be discussed.

Speaker: Martin Sterrer (Institute of Physics, University of Graz, Austria)

11:50 Group Discussion

12:30 Lunch

Social Program

18:30 Dinner

Thursday, 22 February

08:00 Breakfast

4. Thursday Morning

10 Seeing is Believing: Atomic-scale Imaging of Catalysts under Reaction Conditions

The atomic-scale structure of a catalyst under reaction conditions determines its activity, selectivity, and stability. Recently it has become clear that essential differences can exist between the behavior of catalysts under industrial conditions (high pressure and temperature) and the ultra)high vacuum conditions of traditional laboratory experiments. Differences in structure, composition, reaction mechanism, activity, and selectivity have been observed. These observations indicated the presence of the so-called pressure gap, and made it clear that meaningful results can only be obtained at high pressures and temperatures. However, most of the techniques traditionally used to study catalysts and their reactions were designed to operate under (ultra)high vacuum conditions. To bridge the pressure gap, the last years have seen a tremendous effort in designing new instruments and adapting existing ones to be able to investigate catalysts in situ under industrially relevant conditions. In this talk, I will give an overview of the in situ imaging techniques we use to study the structure of model catalysts under industrial conditions of atmospheric pressures and elevated temperatures. We have developed set-ups that combine an ultrahigh vacuum environment for model catalyst preparation and characterization with a high-pressure flow reactor cell, integrated with either a scanning tunneling microscope or an atomic force microscope. With these set-ups we are able to perform atomic-scale investigations of well-defined model catalysts under industrial conditions. Additionally, we combine the structural information from scanning probe microscopy with time-resolved mass spectrometry measurements on the gas mixture that leaves the reactor. In this way, we can correlate structural changes of the catalyst due to the gas composition with its catalytic performance. Furthermore, we use other in situ imaging techniques such as transmission electron microscopy, surface X-ray diffraction, and optical microscopy, all combined with mass spectrometry. This talk highlights a short overview of the instruments we developed and illustrates their performance with results obtained for different model catalysts and reactions. As a proof of principle, results for the fruit fly of surface science, i.e. CO oxidation, will be shown. But additionally, results for more complex reactions such as NO oxidation and reduction, Fischer-Tropsch synthesis, and hydrodesulfurization will be discussed.

Speaker: Dr Irene Groot (Leiden Institute of Chemistry, Netherlands)

11 Complex Heterogeneous Catalysts in Reactive Environment: from Density Functional Theory Simulations to Predictive Kinetic Models

Most efficient heterogeneous catalysts used industrially are generally very complex systems. Far away from perfect crystallinity and well-defined oriented surfaces at low coverage, they involve structural disorder, heterogeneous site distribution with variable coordination and structural dependence upon the chemical environment. Unravelling their atomic-scale structures and understanding their roles in the catalytic reaction are not easy tasks, as the respective contributions of each type of site to the spectroscopic or catalytic responses are generally convoluted. Computational chemistry is of great help to address these issues, but very often, simple structural models are proposed to understand catalytic reactions. In the present manuscript, we show how Density Functional Theory (DFT) calculations were used to provide an original information about the structure for active sites of complex catalytic systems of industrial relevance, as a function of their environment, to assign spectroscopic observations and to quantify the kinetics of multi-step reactions they can catalyze.[1] Heterogeneous catalysts involved in industrial applications such as refining, petrochemistry, biomass conversion and pollution abatement were considered. In particular, original models of imperfect aluminosilicates were developed and their Brønsted acidity unraveled.[2] The reactive environment-dependent (hydrogen and hydrocarbons) morphology of subnanometric platinum-based clusters was revealed.[3] Finally, we show how ab initio thermodynamic and kinetic information can be introduced in kinetic models, possibly integrated themselves in Computational Fluid Simulations, to access macroscopic predictions thanks to a multiscale approach.[4]

References
[1] C. Chizallet, P. Raybaud, Catal. Sci. Technol. 2014, 4, 2797.
[2] C. Chizallet, P. Raybaud, Angew. Chem. Int. Ed. 2009, 48, 2891 ; F. Leydier, C. Chizallet, D. Costa, P. Raybaud, J. Catal. 2015, 325 ; M.-C. Silaghi, C. Chizallet, J. Sauer, P. Raybaud, J. Catal. 2016, 339, 242.
[3] C. Mager-Maury, G. Bonnard, C. Chizallet, P. Sautet, P. Raybaud, ChemCatChem 2011, 3, 200 ; A. Gorczyca, V. Moizan, C. Chizallet, O. Proux, W. Del Net, E. Lahera, J. L. Hazemann, P. Raybaud, Y. Joly, Angew. Chem., Int. Ed 2014, 53, 12426.
[4] K. Larmier, A. Nicolle, C. Chizallet, N. Cadran, S. Maury, A.-F. Lamic-Humblot, E. Marceau, H. Lauron-Pernot, ACS Catalysis 2016, 6, 1905 ; K. Larmier, C. Chizallet, S. Maury, N. Cadran, J. Abboud, A. F. Lamic-Humblot, E. Marceau, H. Lauron-Pernot, Angew. Chem. Int. Ed. 2017, 56, 230.

Speaker: Dr Céline Chizallet (IFP Energies nouvelles, France)

10:40 Coffee Break

12 About Catalytically Active Sites

Catalysts often consist of nano-sized catalyst particles on an support. It has been recognized since long that the role of the support is not only to stabilize the catalytically active particles of particular size, shape and composition, but that they may actively participate in the catalytic reaction. Specific reaction steps may occur completely on the support or at the metal-support interface. In other cases, the support may be responsible for the communication between different catalytic entities by stabilizing and facilitating transport of species over its surface, a process called spillover.

In my talk, I will describe some of our contributions in this field. Ceria is an often-used catalyst support and catalytic material because of its ability to reversibly store oxygen. Thus, in oxidation reactions, oxygen activation may occur on ceria and the reaction at the interface of metal and support. The role of $\rm Ce^{3+}$ is often invoked to explain catalytic activity, however, a quantitative understanding of its role is lacking. Using transient X-ray emission and absorption spectroscopy, we were able to distinguish between $\rm Ce^{3+}$ that participates in a catalytic cycle, oxidation of carbon monoxide over $\rm Pt/CeO_2$, and $\rm Ce^{3+}$ that does not contribute to catalytic conversion and is thus a spectator. The reaction takes place at the metal-support interface and the rate of reaction correlates to the rate of ceria reduction, not the oxygen storage capacity.

Spillover of hydrogen over reducible and non-reducible supports is often suggested to be responsible for a catalytic action at a distance. To quantify the phenomenon of hydrogen spillover, we designed a supported metal catalyst, which contains platinum and iron oxide particles with a distance that is controlled to a nanometer. The further development of single-particle spectroscopy enabled visualization of the phenomenon of hydrogen spillover. As expected, hydrogen atoms can freely move over a titania surface as electron-proton pair. On alumina, the situation is more complex and a gradient of hydrogen coverage away from the platinum particle is observed. The strong competition of water with the same adsorption sites, make the occurrence of hydrogen spillover over an alumina surface much less likely.

Speaker: Prof. Jeroen A. van Bokhoven (ETH Zurich / Paul Scherrer Institute, Switzerland)

11:50 Group Discussion

12:30 Lunch

5. Thursday Evening

13 Real-space Observation of Energy Transfer between Two Molecules by Single-molecule Emission/Absorption Spectroscopy with an STM

Excitation of molecules by light irradiation triggers various important processes including luminescence, photovoltaic effect and photochemical reactions, and detailed understanding of the molecular excited states is crucial to improve organic opto-electronic devices. Absorption spectroscopy is a powerful tool to describe the molecular excitations and the combination with emission (luminescence) spectroscopy which deals with deexcitation processes is effective to investigate the excited states. Single-molecule luminescence detection has progressed rapidly and become indispensable in quantum physics, physical chemistry, and biophysics. However, despite considerable effort and progress, absorption spectroscopy is far behind; numbers of molecules are still necessary to obtain an absorption spectrum. A difficulty lies in the difference between the diffraction limit of excitation light and absorption cross section of a single molecule.
Here I introduce our recent progress in measurement of the single molecule luminescence and absorption spectra of a single molecule using a scanning tunnelling microscope (STM) equipped with optical detection facilities. I will discuss about the single molecule reaction of a single metal-free phthalocyanine molecule on the NaCl ultrathin film on Ag(111) with tunneling electrons and accompanied optical property changes in a single-molecule optical spectra. Application of the single-molecule emission/absorption spectroscopy to the real-space investigation of energy transfer between molecules will be also introduced.

References
[1] H. Imada, K. Miwa, M. Imai-Imada, S. Kawahara, K. Kimura and Y. Kim, Nature 538 (2016) 364.
[2] H. Imada, K. Miwa, M. Imai-Imada, S. Kawahara, K. Kimura and Y. Kim, Phys. Rev. Lett. 119 (2017) 013901.

Speaker: Dr Yousoo Kim (RIKEN, Japan)

14 Multifunctionality Through Interfacial Multiferroicity

Interfacing materials results a wealth of emergent physical properties that can be exploited for new functionalities of the coupled sample. This contribution will concentrate on the interfaces of two ferroic materials such as ferroelectric/ferromagnetic/or ferroelastic compounds. Thereby, the ferroic order itself can be an emergent one due to interfacial proximity effects. After a discussion of the underlying physics, emphasis is put on prospect applications of such composite systems in (opto)electronics as well as in energy saving and conversion devices, such as four-point and non-volatile memories, electrically-driven ultrafast magnetism, thermal diodes, and multiferroic nanoscale heat engines.

Speaker: Prof. Jamal Berakdar (MLU Halle, Germany)

15:40 Coffee Break

15 Colossal Terahertz Magnetoresistance in Oxide Nanocomposites

Conventional materials have magnetoresistances $\Delta R/R=[R(B)-R(0)]/R(0)$ of a few percent, and the giant magnetoresistance of metal heterostructures approaches 30% for dc fields and at THz frequencies [1]. In contrast, in colossal magnetoresistance (CMR) oxides the resistance can change by orders of magnitude in a magnetic field. Here we report for the first time that colossal magnetoresistance persists to THz frequencies, with magnetoresistances above -99% at 1THz and at room temperature [2].

The THz magneto-optical conductivity of the colossal magnetoresistance compound $\mathrm{La}_{0.7}\mathrm{Sr}_{0.3}\mathrm{MnO}_3$ was investigated by THz time-domain spectroscopy. The response of vertically-aligned nanocolumns of $\mathrm{La}_{0.7}\mathrm{Sr}_{0.3}\mathrm{MnO}_3$ in a ZnO matrix [3] was compared with that of pure $\mathrm{La}_{0.7}\mathrm{Sr}_{0.3}\mathrm{MnO}_3$ thin films. This is particularly important as it allows the comparison of the intrinsic CMR effect, witnessed in pure single crystals around room temperature, with the extrinsic CMR effect, which is controlled by grain boundaries. Extrinsic CMR requires lower applied magnetic fields than the intrinsic effect, desirable for applications, but works below room temperature. Surprisingly, and in contrast to the dc CMR effect, we demonstrate that the THz magneto-optical response in $\mathrm{La}_{0.7}\mathrm{Sr}_{0.3}\mathrm{MnO}_3$ nanocolumns is an intrinsic effect. The THz CMR is large at the Curie temperature, when core Mn spins begin to align ferromagnetically, but decreases at lower temperatures.

At temperatures below the metal-insulator transition (when samples are metallic) the frequency-dependent conductivity is well described by the Drude model of free-carrier absorption. The application of a magnetic field perpendicular to the samples was found to enhance the Drude spectral weight, which can be understood within the double-exchange picture of charge transport in the CMR manganites. At the Curie temperature (300K) the THz conductivity of the nanocolumn film was dramatically enhanced by the application of a magnetic field, creating a non-Drude conductivity that increases with frequency. We discuss possible origins of this trend, including the prevalent picture in the literature of bipolarons destruction under a magnetic field into single polarons. The observed colossal THz magnetoresistance suggests that the magnetoresistance can be large for ac motion on nanometre length scales, even when the magnetoresistance is negligible on the macroscopic length scales probed by dc transport. Colossal THz magnetoresistance at THz frequencies may find use in active THz optical and electronic components controlled by magnetic fields.

References
[1] Z. Jin et al., Nat. Phys. 11, 761 (2015).
[2] J. Lloyd-Hughes et al., Nano Letters 17, 2506 (2017).
[3] A. Chen et al., Adv. Funct. Mater. 21, 2423 (2011).

Speaker: Prof. James Lloyd-Hughes (University of Warwick, UK)

16:50 Group Discussion

18:30 Bavarian Dinner

8. Poster Session II

Friday, 23 February

08:00 Breakfast

6. Friday Morning

16 A Transition from Academia to Industry: How Model Surfaces and Catalysts turned to Tablets, Optics Technology, and Project Management

With the final months of the PhD coming closer, every graduate needs to make a decision about his or her future: pursue a career in science or in the private sector?

While graduates are familiar with the academic environment after several years of research at universities or other scientific institutions, the private sector remains a big unknown to many. So, how do you make a sound choice? Which is more suiting to your interests, personality, goals, and way of life?

In my talk I will provide you with my personal point of view: why I chose to work in industry, how things turned out as an industrial researcher, and how my career has developed ever since. An introduction to the technological problems that I faced trying to improve the performance of potassium hyperoxide based respiratory protection systems as well as optical coating technology will be given.

More importantly, I want to share my experience related to the way of working in industry and how it has shaped my thinking.

Speaker: Dr Stefan Schernich (Carl Zeiss SMT GmbH)

17 What Do Editors Do All Day?

From the perspective of an editor, John Uhlrich (Editor-in-Chief, Energy Technology), will present on the current state of publishing in the physical sciences and energy research, including chemistry, materials science, and engineering, by outlining the roles, responsibilities, and ethical obligations of authors, editors, and reviewers. The talk will include offer tangible examples and how-to's related to publishing in journals and communication between authors, editors, and reviewers. An introduction to the Wiley-VCH journals will be presented along with some tips for preparing scientific publications and how to achieve the highest possible impact after publication.

Speaker: John Uhlrich (Wiley-VCH)

10:40 Coffee Break & Conclusion

12:30 Lunch