TY - JOUR AU - Kunnathully, Vinay S. AU - Riedl, Thomas AU - Trapp, Alexander AU - Langer, Timo AU - Reuter, Dirk AU - Lindner, Jörg K.N. ID - 17434 JF - Journal of Crystal Growth SN - 0022-0248 TI - InAs heteroepitaxy on nanopillar-patterned GaAs (111)A ER - TY - JOUR AU - Geier, M. AU - Freudenfeld, J. AU - Silva, J. T. AU - Umansky, V. AU - Reuter, Dirk AU - Wieck, A. D. AU - Brouwer, P. W. AU - Ludwig, S. ID - 17435 JF - Physical Review B SN - 2469-9950 TI - Electrostatic potential shape of gate-defined quantum point contacts ER - TY - JOUR AB - The study of electron transport in low-dimensional systems is of importance, not only from a fundamental point of view, but also for future electronic and spintronic devices. In this context heterostructures containing a two-dimensional electron gas (2DEG) are a key technology. In particular GaAs/AlGaAs heterostructures, with a 2DEG at typically 100 nm below the surface, are widely studied. In order to explore electron transport in such systems, low-resistance ohmic contacts are required that connect the 2DEG to macroscopic measurement leads at the surface. Here we report on designing and measuring a dedicated device for unraveling the various resistance contributions in such contacts, which include pristine 2DEG series resistance, the 2DEG resistance under a contact, the contact resistance itself, and the influence of pressing a bonding wire onto a contact. We also report here a recipe for contacts with very low resistance values that remain below 10 Ω for annealing times between 20 and 350 s, hence providing the flexibility to use this method for materials with different 2DEG depths. The type of heating, temperature ramp rate and gas forming used for annealing is found to strongly influence the annealing process and hence the quality of the resulting contacts. AU - Javaid Iqbal, Muhammad AU - Reuter, Dirk AU - Wieck, Andreas Dirk AU - van der Wal, Caspar ID - 17436 JF - The European Physical Journal Applied Physics SN - 1286-0042 TI - Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure ER - TY - JOUR AU - Ebler, C. AU - Labud, P. A. AU - Rai, A. K. AU - Reuter, Dirk AU - Wieck, A. D. AU - Ludwig, A. ID - 17437 JF - Physical Review B SN - 2469-9950 TI - Electrical detection of excitonic states by time-resolved conductance measurements ER - TY - JOUR AB - Compact and robust cold atom sources are increasingly important for quantum research, especially for transferring cutting-edge quantum science into practical applications. In this study, we report on a novel scheme that uses a metasurface optical chip to replace the conventional bulky optical elements used to produce a cold atomic ensemble with a single incident laser beam, which is split by the metasurface into multiple beams of the desired polarization states. Atom numbers ~107 and temperatures (about 35 μK) of relevance to quantum sensing are achieved in a compact and robust fashion. Our work highlights the substantial progress toward fully integrated cold atom quantum devices by exploiting metasurface optical chips, which may have great potential in quantum sensing, quantum computing, and other areas. AU - Zhu, Lingxiao AU - Liu, Xuan AU - Sain, Basudeb AU - Wang, Mengyao AU - Schlickriede, Christian AU - Tang, Yutao AU - Deng, Junhong AU - Li, Kingfai AU - Yang, Jun AU - Holynski, Michael AU - Zhang, Shuang AU - Zentgraf, Thomas AU - Bongs, Kai AU - Lien, Yu-Hung AU - Li, Guixin ID - 17523 IS - 31 JF - Science Advances SN - 2375-2548 TI - A dielectric metasurface optical chip for the generation of cold atoms VL - 6 ER - TY - JOUR AU - Schweizer, Swetlana AU - Becker-Staines, Anna AU - Tröster, Thomas ID - 17578 JF - Waste Management SN - 0956-053X TI - Separation and reclamation of automotive hybrid structures made of metal and fibre-reinforced plastic ER - TY - JOUR AU - Sonnenrein, G. AU - Baumhögger, Elmar AU - Elsner, A. AU - Morbach, A. AU - Neukötter, M. AU - Paul, A. AU - Vrabec, J. ID - 17589 JF - International Journal of Refrigeration SN - 0140-7007 TI - Improving the performance of household refrigerating appliances through the integration of phase change materials in the context of the new global refrigerator standard IEC 62552:2015 ER - TY - GEN AB - Syntactic annotation of corpora in the form of part-of-speech (POS) tags is a key requirement for both linguistic research and subsequent automated natural language processing (NLP) tasks. This problem is commonly tackled using machine learning methods, i.e., by training a POS tagger on a sufficiently large corpus of labeled data. While the problem of POS tagging can essentially be considered as solved for modern languages, historical corpora turn out to be much more difficult, especially due to the lack of native speakers and sparsity of training data. Moreover, most texts have no sentences as we know them today, nor a common orthography. These irregularities render the task of automated POS tagging more difficult and error-prone. Under these circumstances, instead of forcing the POS tagger to predict and commit to a single tag, it should be enabled to express its uncertainty. In this paper, we consider POS tagging within the framework of set-valued prediction, which allows the POS tagger to express its uncertainty via predicting a set of candidate POS tags instead of guessing a single one. The goal is to guarantee a high confidence that the correct POS tag is included while keeping the number of candidates small. In our experimental study, we find that extending state-of-the-art POS taggers to set-valued prediction yields more precise and robust taggings, especially for unknown words, i.e., words not occurring in the training data. AU - Heid, Stefan Helmut AU - Wever, Marcel Dominik AU - Hüllermeier, Eyke ID - 17605 T2 - Journal of Data Mining and Digital Humanities TI - Reliable Part-of-Speech Tagging of Historical Corpora through Set-Valued Prediction ER - TY - GEN AB - Employing a unique sample of 2,849 tariff imposition announcements by and against the United States (U.S.) over the period from 2018 to 2019, this study analyzes the impact of recent tariff announcements on share prices from 859 U.S. companies. We provide evidence for negative (cumulative) average abnormal stock returns due to tariff announcements during a symmetric three-day event window. We suggest that stock market investors expect adverse impacts of tariff impositions, e.g. a decrease in the companies' future cash flows and a threat of retaliation. The negative wealth effects are observed irrespective of whether the Trump administration announces safeguard tariffs to protect domestic firms or a retaliation is declared by foreign countries. Moreover, building several subsamples, we find that the adverse impact is mostly driven by announcements involving China and is associated with a variety of sector, tariff, trade and firm characteristics. AU - Wengerek, Sascha Tobias ID - 17703 KW - event study KW - international relations KW - protectionism KW - strategic trade policy KW - tariffs KW - trade conflict TI - Share price reactions to tariff imposition announcements in the Trump era - An event study of the trade conflict ER - TY - JOUR AU - Ortmann, Regina AU - Pelster, Matthias AU - Wengerek, Sascha Tobias ID - 17730 JF - Finance Research Letters SN - 1544-6123 TI - COVID-19 and investor behavior VL - 37 ER -