1st metaMAT anniversary meeting, Tuesday 27 July 2021, 14:00 (London Time)
Speaker 1: Martin Wegener (Karlsruhe Institute of Technology)
Title: Roton Metamaterials
Abstract: Based on the pioneering work of Lev Landau and Richard Feynman, rotons were observed in inelastic neutron scattering experiments on superfluid helium in 1961. For the roton dispersion relation, energy and momentum of the acoustical wave are proportional to each other for small momenta. For larger momenta, a (roton) minimum of energy versus momentum occurs. Rotons have also been investigated in other correlated quantum systems at low temperatures, such as quasi two-dimensional thin films of 3He, quantum Hall effect stripes in semiconductors, and Bose-Einstein condensates of atoms. In this talk, we present the physics and design of metamaterials showing roton dispersion relations under ambient conditions.
Biography: After completing his Diplom and PhD in physics at Johann Wolfgang Goethe-Universität Frankfurt (Germany) in 1986 and 1987, respectively, he spent two years as a postdoc at AT&T Bell Laboratories in Holmdel (U.S.A.). From 1990-1995 he was professor (C3) at Universität Dortmund (Germany), since 1995 he is professor (C4, later W3) at Institute of Applied Physics of Karlsruhe Institute of Technology (KIT). Since 2001 he has a joint appointment as department head at Institute of Nanotechnology (INT) of KIT, since 2016 he is one of three directors at INT. From 2001-2014 he was the coordinator of the DFG- Center for Functional Nanostructures (CFN) at KIT. Since 2018 he is spokesperson of the Cluster of Excellence 3D Matter Made to Order. His research interests comprise ultrafast optics, (extreme) nonlinear optics, optical laser lithography, photonic crystals, optical, mechanical, electronic, and thermodynamic metamaterials, as well as transformation physics. This research has led to various awards and honors, among which are the Alfried Krupp von Bohlen und Halbach Research Award 1993, the Baden- Württemberg Teaching Award 1998, the DFG Gottfried Wilhelm Leibniz Award 2000, the European Union René Descartes Prize 2005, the Baden-Württemberg Research Award 2005, the Carl Zeiss Research Award 2006, the Hector Research Award 2008, the SPIE Prism Award 2014 for the start-up company Nanoscribe GmbH, the Stifterverband Science Award – Erwin-Schrödinger Prize 2016, and the Technology Transfer Prize of the German Physical Society (DPG) 2018. In 2014, 2015, 2016, 2017, 2018, and 2020 Clarivate Analytics listed him as “Highly Cited Researcher” (top 1%). He is Member of Leopoldina, the German Academy of Sciences (since 2006), Member of acatech, the National Academy of Science and Engineering (since 2019), Member of the Hector Fellow Academy (since 2013, presently also President), Fellow of the Max Plack School of Photonics (since 2019), Fellow of the Optical Society of America (since 2008), and Honorary Professor at Huazhong University of Science & Technology, Wuhan, China (since 2014).
& Seminar 52, Tuesday 27 July 2021, 17:00 (London Time)
Speaker 2: Tadashi Tokieda (Department of Mathematics, Stanford University, California, USA)
Title: Toy models
Abstract: Would you like to come see some toys?
‘Toys’ here have a special sense: objects of daily life which you can find or make in minutes, yet which, if played with imaginatively, reveal surprises that keep scientists puzzling for a while.
We will see table-top demos of a diversity of such toys, in which we will notice new effects, from which we will try to extract some fresh, simple models. A common theme that emerges is singularity. (This was given as a public lecture at the International Congress of Mathematicians in Rio de Janeiro, 2018.)
photo by Jessica Wynne
Biography: Tadashi Tokieda grew up as a painter in Japan, became a classical philologist (not to be confused with philosopher) in France, before switching to mathematics and later physics. Having lived in 8 countries, he is now a professor of mathematics at Stanford; previously he worked for many years at Cambridge. He is also active in outreach in the developing world, especially via African Institute for Mathematical Sciences.
Seminar S2-5, Tuesday 5 October 2021, 14:00 (London Time)
Speaker: Corentin Coulais (Van der Waals-Zeeman Instituut, Faculty of Science, University of Amsterdam, Netherland)
Seminar S2-6, Tuesday 12 October 2021, 14:00 (London Time)
Speaker: Johan Christensen (Department of Physics, Universidad Carlos III de Madrid, Spain)
Seminar S2-7, Tuesday 19 October 2021, 14:00 (London Time)
Speaker: Ornella Mattei (Department of Mathematics, San Francisco State University, USA)
Seminar S2-8, Tuesday 26 October 2021, 14:00 (London Time)
Speaker: Alexei Maznev (Department of Chemistry, Massachusetts Institute of Technology, Cambridge MA 02139, USA)
Title: Self-collimation, Veselago lens, Dirac cones and embedded states in continuum in acoustics without phononic crystals and metamaterials
Self-collimation a.k.a. phonon focusing of surface acoustic waves on Ge (111)
Abstract: The concepts of photonic crystals and metamaterials initially appeared in optics and electromagnetism, and were subsequently extended to acoustic waves. However, a number of phenomena thought to be specific to these “artificial” media have been observed in solid state acoustics with conventional materials – in some cases well before the advent of metamaterials and photonic/phononic crystals. In this talk, which will cover both historical and recent research, we will discuss several such phenomena: (i) “self-collimation” of bulk and surface acoustic waves in natural crystals; (ii) negative group velocity, Veselago lens and Dirac cones exhibited by guided acoustic waves in plates; (iii) robust embedded states in continuum on natural crystal surfaces and in simple layered structures.
Biography: Alex Maznev received Diploma in physics from the Moscow Institute of Physics and Technology and PhD from the General Physics Institute of the Russian Academy of Sciences (thesis on laser-generated SAWs including the first experimental observation of surface phonon focusing). He held postdoctoral positions at the Freie Universität Berlin, as an Alexander von Humboldt Fellow, and at MIT, where he developed an optical heterodyning scheme for laser-induced transient grating experiment currently used in many labs. Subsequently, he worked as an industrial researcher (mainly at Philips Electronics North America) developing metrology systems for semiconductor industry using optical and optoacoustic techniques, before returning to MIT as a staff scientist. His current interests involve a broad range of topics pertaining to wave propagation phenomena, primarily in acoustics and related fields such as phonon-mediated heat transport on micro/nanoscale. He is collaborating with many groups around the world and has held visiting positions at Université du Maine in France, Hokkaido University in Japan, University of Witwatersrand in South Africa, and Universität Heidelberg in Germany.