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Frankfurt theoreticians investigate puzzling phenomenon in a quantum gas
FRANKFURT. Insulators that are conducting at their edges hold promise for interesting technological applications. However, until now their characteristics have not been fully understood. Physicists at Goethe University have now modelled what are known as topological insulators with the help of ultracold quantum gases. In the current issue of Physical Review Letters, they demonstrate how the edge states could be experimentally detected.
Imagine a disc made of an insulator with a conducting edge along which a current always flows in the same direction. “This makes it impossible for a quantum particle to be impeded, because the state of flowing in the other direction simply doesn't exist," explains Bernhard Irsigler, the first author of the study. In other words: in the edge state, the current flows without resistance. This could be used, for example, to increase the stability and energy efficiency of mobile devices. Research is also being done on how to use this to construct lasers that are more efficient.
In recent years, topological insulators have also been produced in ultracold quantum gases in order to better understand their behaviour. These gases result when a normal gas is cooled down to temperatures between a millionth and billionth of a degree above absolute zero. This makes ultracold quantum gases the coldest places in the universe. If an ultracold quantum gas is also produced in an optical lattice made of laser light, the gas atoms arrange themselves as regularly as in the crystal lattice of a solid. However, unlike a solid, many parameters can be varied, allowing artificial quantum states to be studied.
“We like to call it a quantum simulator because this kind of system reveals many things that take place in solids. Using ultracold quantum gases in optical lattices, we can understand the basic physics of topological insulators," explains co-author Jun-Hui Zheng.
A significant difference between a solid and a quantum gas, however, is that the cloud-shaped gases do not have defined edges. So how does a topological insulator in an ultracold gas decide where its edge states are? The researchers in Professor Walter Hofstetter's research group at the Institute for Theoretical Physics at Goethe University answer this question in their study. They modelled an artificial barrier between a topological isolator and a normal isolator. This represents the edge of the topological insulator along which the conducting edge state forms.
“We demonstrate that the edge state is characterized through quantum correlations that could be measured in an experiment using a quantum gas microscope. Harvard University, MIT and the Max-Planck-Institute for Quantum Optics in Munich all carry out these kinds of measurements," says Hofstetter. A quantum gas microscope is an instrument with which individual atoms can be detected in experiments. “For our work, it is critical that we explicitly take into account the interaction between the particles of the quantum gas. That makes the investigation more realistic, but also much more complicated. The complex calculations could not be carried out without a supercomputer. The close collaboration with leading European scientists within the context of the DFG Research Unit 'Artificial Gauge Fields and Interacting Topological Phases in Ultracold Atoms' is also of particular importance for us," Hofstetter adds.
Publication: Bernhard Irsigler, Jun-Hui Zheng, and Walter Hofstetter: Interacting Hofstadter interface, Physical Review Letters, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.010406
A picture can be downloaded at: http://www.uni-frankfurt.de/75773481
Caption: Artificial edge in an optical lattice (blue), filled with an ultracold quantum gas that consists of 'spin-up' particles (red) and 'spin-down' particles (green). Along the edge – and only there - 'spin-up' particles can only flow to the left, and 'spin-down' particles can only flow to the right. Credit: Bernhard Irsigler
Further Information: Bernhard Irsigler, Institute for Theoretical Physics, Riedberg Campus, Tel.: +49 69-798 47883, email@example.com .
A common mineral found in super-deep diamonds has been named after the Frankfurt mineralogist and petrologist
FRANKFURT. Diamonds are messengers from Earth's interior. A portion of the rare gem, which is very small but important for researchers, contains inclusions from the earth's lower mantle. One of the most common minerals brought to the Earth's surface in this way has now been named “breyite" by the Commission of the “International Mineralogical Association" in honour of the mineralogist Professor Gerhard Brey from Goethe University.
The interior of the Earth is largely inaccessible for sample recovery. Intensive drilling efforts can reach a maximum depth of 12 kilometres, which represents a mere scratching on the surface. Volcanoes, on the other hand, can transport samples from significantly deeper zones to the Earth's surface. The samples that come from the greatest depths are inclusions of minerals and rock fragments in valuable diamonds. These inclusions were one of the fields of research of Gerhard Brey, meanwhile retired Professor for Petrology and Geochemistry at the Institute for Geosciences at Goethe University.
According to prevalent theories, Earth's lower mantle (at a depth of 660 – 2900 kilometres) consists almost exclusively of the three minerals silicate perovskite, ferropericlase, and a mineral rich in calcium and silicon with a perovskite structure. When diamonds form at this depth, it can happen that they trap this mineral. During transport to the earth's surface, the calcium-silicon perovskite converts to a new crystal structure that is stable at lower pressure. This mineral is only known as inclusion in diamonds. It now bears the name breyite.
“Having a mineral named after you is a very special honour and pays tribute to the life work of a scientist in a special and lasting way," states Brey's colleague, the geoscientist Professor Frank Brenker. “Especially when we're talking about such an important Earth mineral.
Gerhard Brey's name is now forever carved in stone, so to speak." Gerhard Brey, who retired in 2014, is considered a pioneer in experimental petrology under high-pressure conditions. He achieved world recognition through the development and calibration of geothermobarometers for rocks in the earth's mantle. These thermobarometers are not only crucial aids in researching the Earth's interior, they are also very popular in the search for new diamond deposits. While it used to be necessary to process tons of rocks to determine whether the deposit in question really contained diamonds, now only a few grains of mineral are necessary.
In addition to thermobarometric calculations, Brey is interested in the solubility of fluids and gases, including their influence on the formation of magmas. Along with other colleagues, he was one of the first researchers to recognize the scientific value of inclusions in diamonds with origin depths of hundreds of kilometres. Brey has received a numerous distinctions, including an honorary doctorate from the Russian Academy of Sciences and the Abraham-Gottlob-Werner silver medal, which he was awarded by the German Mineralogical Society for his life's work.
A picture may be downloaded at: www.uni-frankfurt.de/75659882
Caption: Breyite inclusion in a Brazilian diamond with “super-deep“ origins.
Credit: Brenker, Goethe University Portraits of Gerhard Brey: private
Further Information: Professor Frank Brenker, Institute for Geosciences, Mineralogy, Riedberg Campus, Tel.: (069)-798 40134, firstname.lastname@example.org.
Goethe University and partner universities want to form network as “European University“ – “Trust through mobility“ as central theme
FRANKFURT. Goethe University has joined ranks with universities in Milan, Lyon and Birmingham to form an alliance of European universities for more intensive cooperation in the future. In February they will together apply for the title “European University” and funding by the EU. On Monday and Tuesday, the partners met in Frankfurt to discuss goals and opportunities of the collaboration.
“This application for ‘European University’ is a great opportunity for Goethe University,” said Professor Rolf van Dick, Vice President of Goethe University and responsible for international affairs, speaking informally during the meeting. As European University, networking in Europe would be strengthened and scientific and non-scientific projects could be tackled.
Three to five universities can apply together for the title “European University” with the European Commission. Important requirements are a common, long-term education strategy; a common (virtual) “European Campus”; and research and a student body characterized by diversity that can place their focus on the challenges of the future. Goethe University already has a partnership with the University of Birmingham, the Université Lumière Lyon II and Sciences Po Lyon, and the Università Cattolica del Sacro Cruce in Milan, and as partner cities, all four cities are furthermore on friendly and familiar terms. As “European University”, their cooperation could be intensified and made more concrete. If successful, the consortium will receive funding amounting to € 5 million for an initial three years.
In a well-received speech in September 2017, French President Emmanuel Macron proposed the creation of 20 European universities by 2024, referring to networking and alignment between existing European universities as opposed to the creation of new institutions. In difficult times for the European Union, university science and scholarship should be strengthened as an important engine for European integration. This would enable the younger generation, in particular, to again develop a stronger connection to the project of Europe. But scientific knowledge and learning are in general of great significance for developing a European identity – as manifested in the past by examples such as the Erasmus exchange programme, and collaborative research projects funded by the EU.
Macron affirmed his ideas impressively at Goethe University in October 2017. “It really inspired all of us,” says van Dick. In April, a task force was created, headed by van Dick. “It’s exciting, actually,” said James Walker from the Université Lumière Lyon II, praising Goethe University’s initiative. “We quickly found ourselves on the same page regarding our objectives and values. It almost doesn’t matter if our application isn’t successful. We’ll cooperate anyway,” says Walker. “It’s vital for us, as universities, to work together. If we cannot cooperate, how can we expect it of our politicians?” said Michael Whitby from the University of Birmingham, alluding to the Brexit crisis. And Edilio Mazzolini from Università Cattolica in Milan is “proud to be a part of this network“, because the identity of his university is “deeply European“.
Mobility, the meeting summed up, should be a central issue of the European University. Mobility of students, of scientific and non-scientific personnel, and also the mobility of ideas. The universities face similar challenges, for example in teaching, and together they will be able find better solutions. Birmingham has been a strategic partner for years; cooperation between the faculties of law and economics has existed for several years with Université Lumière Lyon II; with Sciences Po Lyon there is a lively partnership between the political science faculties; and Goethe University has a common master’s degree in film studies with Milan.
An image may be downloaded at: www.muk.uni-frankfurt.de/75375741
Further information: Andrea Grebe, Office of the Vice President Professor Rolf van Dick, Tel: -49 69 798-12242, E-Mail: email@example.com
Economist Nicola Fuchs-Schündeln awarded € 1.6 million ERC Consolidator Grant
FRANKFURT. Why do some groups behave differently in the labour market than others? What determines labour market success? And which effect do public policies have in this context? These questions are at the centre of a new research project by Frankfurt economist and Leibniz Award winner Nicola Fuchs-Schündeln. The project has been made possible by the European Research Council (ERC)’s Consolidator Grant, one of the largest awards funding scientific research in the European Union. It has just been announced that Fuchs-Schündeln, who is currently in Australia for a research sabbatical, will receive a Consolidator Grant this year. Her project is titled: “Macro- and Microeconomic Analyses of Heterogeneous Labor Market Outcomes.”
“For the second time within a very brief period, I have the pleasure of congratulating Nicola Fuchs-Schündeln on an impressive distinction,” comments University President Birgitta Wolff. “Following the Leibniz Prize from the Deutsche Forschungsgemeinschaft (German Research Foundation), this exceptional economist has now also brought an ERC Consolidator Grant to Frankfurt, which is an enormous success. It demonstrates the great recognition Fuchs-Schündeln enjoys also in the international research community. We are happy to have a colleague like her, with her innovative research approach, among us. In her research, she combines macro- and microeconomic methods and directs her view towards unconventional and innovative questions – a great enrichment for scientific dialogue and for Goethe University.”
Since 2009, Nicola Fuchs-Schündeln has been Professor for Macroeconomics and Development at Goethe University Frankfurt. She is a principle investigator in the Excellence Cluster “The Formation of Normative Orders”, as well as in the LOEWE Centre “Sustainable Architecture for Finance in Europe”. From 2015 to 2016, she was a Visiting Professor at Stanford University in California. Fuchs-Schündeln received her Ph.D. from Yale and worked at Harvard as an Assistant Professor of Economics before joining Goethe University. She studied Latin American studies and economics at the University of Cologne.
As in her previous work, in the ERC project “Macro- and Microeconomic Analyses of Heterogeneous Labor Market Outcomes”, Fuchs-Schündeln remains true to her research style of combining macro- and microeconomic methods. The 46 year-old economist plans to carry out four subprojects; three examine differences in labour market behaviour and success of men and women, while the fourth one is concerned with differences in hours worked between poor and rich countries. Labour market data from the Institute for Employment Research (IAB) and the Federal Statistical Office will serve as primary data sources. Individual work biographies, as well as company personnel strategies, can be gleaned from anonymized social insurance data from employees and employers.
One of the subprojects will pursue the question of how maternity leave policies affect the labour market success of women of child-bearing age, explains Fuchs-Schündeln. Although intended as not only family-friendly, but more specifically female-friendly policies, maternity leave policies may have negative consequences, because they could make employers more cautious about employing and promoting women. “These potential negative effects have not been investigated yet,” says the researcher. Such insights are not only of interest for Germany, since maternity leave policies are being discussed and implemented in many countries. Another subproject deals with the phenomenon that an increasing female share in an occupation correlates with decreasing relative wages of this occupation. “There are several hypotheses to explain this: It might be the case that an increasing female share lowers the prestige of an occupation – or the correlation might arise because women place a higher value on amenities such as flexibility, and greater flexibility comes with lower wages,” explains Fuchs-Schündeln. Along with other sources, this research will be based on data from East Germany, where women had made greater advances in technical occupations.
Fuchs-Schündeln will not carry out all this research alone. Several doctoral candidates and a postdoc will be involved in the project. “The research agenda is rather data-intensive,” states the economist. There are enough qualified candidates for these doctoral positions in Frankfurt, Fuchs-Schündeln observes. “At the faculty of economics and business administration, we have a structured doctoral program - the Graduate School of Economics, Finance, and Management, GSEFM - in which we jointly educate and train young researchers. That’s one of Goethe University’s great strengths.” The ERC project will be funded through 2024 with € 1.6 million.
The ERC Consolidator Grant is the latest in a series of honours: At the beginning of 2018, Fuchs-Schündeln won the Leibniz Award, the most prestigious German research award. In 2016, she was given the Gossen Award by the Verein für Socialpolitik (German Economic Association), the most important German award for economics. In 2010 she also already received a Starting Grant from the European Research Council.
A picture may be downloaded here: www.uni-frankfurt.de/75159663
Further information: Professor Nicola Fuchs-Schündeln, Professorship for Macroeconomics and Development, Faculty 02, Theodor-W.-Adorno-Platz 3, Westend Campus, Tel.: -49 69 798-33815, E-Mail: firstname.lastname@example.org.
Significant increase in number of successful scientists in Clarivate Analytics ranking
FRANKFURT. Every year, a list is published of the top one percent of researchers worldwide, based on the frequency with which their work is cited by other scientists according to data from the “Web of Science”. The number of natural and medical scientists from Goethe University on the list increased from three to thirteen in the past year.
Goethe University also stands out in comparison with other German universities: only Heidelberg University has one more researcher listed. The German research institution with the greatest number of highly cited researchers is the Max Planck Institute, which had 76 researchers on the list. A total of 256 researchers form German institutions made it on the list, which includes 6078 researchers in 22 different scientific disciplines.
The most highly cited researchers at Goethe University are atmospheric researcher
Joachim Curtius, biochemist Ivan Dikic, biologist Stefanie Dimmeler, hydrologist Petra Döll, pharmacologist Jennifer Dressman, geographer Thomas Hickler, cardiologist Stefan Hohnloser, pharmacist Stefan Knapp, cancer researcher Sibylle Loibl, medical scientist Christoph Sarrazin, brain researcher Wolf Singer, physicist Ernst Stelzer, and medical scientist Stefan Zeisel.
“Web of science“ is a platform for researching academic literature. It indexes all scientific and reviewed publications, and also determines how frequently each publication is cited. It is operated by the company Clarivate Analytics.
Further information: Prof. Dr. Joachim Curtius, Institute for Geosciences, Riedberg Campus, Tel.: -49 69 798-40258, email@example.com.
List of highly cited researchers: https://hcr.clarivate.com/