Events: Fysik events at Chalmers University of TechnologyWed, 21 Mar 2018 10:46:25 +0100 Physics in HgTe-based Quantum Devices<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​Colloquium by Laurens W. Molenkamp from Würzburg University, Germany</p><h4 class="chalmersElement-H4">Abstract:</h4> <div>Topological insulators are a novel class of materials that exhibit a novel state of matter – while the inside (bulk) of the materials is electrically insulating, their surface is metallic. This effect occurs because the band structure of the materials is topologically different (in a mathematical sense) from the outside world.</div> <div>This talk describes our discovery of this type of behavior while studying the charge transport properties of thin, two-dimensional layers of the narrow-gap semiconductor HgTe. These layers exhibit the quantum spin Hall effect, a quantized conductance which occurs when the bulk of the material is insulating. Using various tricks one can show that the transport occurs along one-dimensional, spin-polarized channels at the edges of the sample.</div> <div>Also thicker HgTe samples can be turned into topological insulators, but now the surface states are two-dimensional metallic sheets. The metal in these sheets is rather exotic in that the band structure is similar to that encountered for elementary particles – the charge is carried by so-called Dirac fermions. This means that experiments on these layers can be used to test certain predictions from particle theory that are difficult to access otherwise.</div> <div>As an example, I will describe experiments where a supercurrent is induced in the surface states by contacting these structures with Nb electrodes. AC investigations indicate that the induced superconductivity is strongly influenced by the Dirac nature of the surface states.We present strong evidence for the presence of a gapless Andreev mode in our junctions.</div> <div>Finally, by playing with the strain in the layers, we can turn HgTe into a Dirac semimetal, which exhibits the ‘axial anomaly’ known from particle physics when the Fermi level is tuned to the Dirac points.</div>'s thesis presentation: Axel Hallenbert<p>N6115, seminar room, Fysik Origo, Fysik</p><p>​Title: Multiscale Modelling of Large-Amplitude Fluctuations in Tokamak Edge Plasmas</p><p></p> <h4 class="chalmersElement-H4">Abstract: </h4> <div>For an efficient and safe operation of magnetic confinement fusion reactors reliable theoretical descriptions of the dynamic behavior of the confined plasma are required. The usually employed gyrokinetic theory, which is a suitable description of the small amplitude turbulence in the plasma core, might be expected to break down in the plasma edge, in the presence of large fluctuations and an extremely steep pressure gradient. In this thesis we explore the transition to large amplitude fluctuations. We do this by using multiscale asymptotics analysis to produce a set of equations describing large amplitude turbulent plasma fluctuations in the edge region. These equations are then shown to smoothly match onto gyrokinetics in the appropriate limits.</div> <p></p> seminar: Joel Magnusson, Physics<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​Title of thesis: Approaches to particle acceleration in intense laser-matter interaction</p><h4 class="chalmersElement-H4">​<span><br />Abstract:</span></h4> <span> </span>In the interaction of ultra-intense laser fields with matter, the target is rapidly ionized and a plasma is formed. The ability of a plasma to sustain acceleration gradients, orders of magnitude larger than achievable with conventional accelerators, has led to a great interest in laser-driven plasma-based particle acceleration and radiation generation, with applications in materials science, biology and medicine. <br /><span><div><br />In this thesis we consider laser-driven plasma-based particle acceleration by studying the interaction of intense laser fields with solid density targets. The basics of such interactions are described and some of the most common acceleration schemes are presented. We study the effect of adding microstructures on the illuminated side of a solid target and show how this affects the resulting distribution of hot electrons. Furthermore, we discuss how to achieve controllable ion acceleration through displacement of electrons by standing waves. A recently proposed laser-driven ion acceleration scheme, called chirped-standing-wave acceleration, is introduced and described in detail. Finally, we analyse the robustness of this acceleration scheme under non-ideal conditions and discuss its prospects and limitations.<br /><br /><strong>Graduate school:</strong> Physics<br /><strong>Main supervisor:</strong> Mattias Marklund</div></span><div><span><strong>Examiner: </strong></span><span><span><strong> </strong>Mattias Marklund<span style="display:inline-block"></span></span></span></div> <div><span><strong>Opponent:</strong> Göran Johansson, MC2, Chalmers<span style="display:inline-block"></span></span></div> Plasmon-enhanced detection of single molecules<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​Seminar by Peter Zijlstra, Eindhoven University of Technology, The Netherlands</p><h4 class="chalmersElement-H4">Abstract:</h4> <div>Optical detection of single molecules mostly relies on their fluorescence because of the high contrast of this technique against the background. However, the majority of native biomolecules such as proteins hardly fluoresce at all, requiring a different approach for their detection. Plasmon-enhanced detection circumvents the need for labeling by allowing direct optical detection of weakly emitting and completely non‐fluorescent species.</div> <div> </div> <div>In the past decade, two mechanisms for plasmon-enhanced single-molecule detection have been demonstrated: (1) by plasmonically enhancing the emission of weakly fluorescent biomolecules, or (2) by monitoring shifts of the plasmon resonance induced by single-molecule interactions. I will outline recent advances in single molecule detection using a single particle approach. I will then describe recent results regarding applications in analytical chemistry and medical diagnostics.</div> seminar: Sergey Novozhilov, Physics<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​Title of thesis: Numerical modelling of time-dependent metamaterials with the FDTD method</p><h4 class="chalmersElement-H4"><br />Abstract:</h4> Metamaterials are artificial materials, usually composed of so-called meta-atoms, with electromagnetic properties which cannot be found in naturally occurring materials. In this work we study the properties of time-dependent metamaterials (meaning that their electromagnetic properties are varying with time), as well as their potential applications. Since the analytical results available are limited, we have developed and implemented a numerical technique based on the Finite-Differences Time-Domain (FDTD) method. The method and its implementation are discussed in detail. A state-of-the-art variation of the total-field / scattered-field technique is used to introduce plane waves into the computational domain, so that numerical artifacts are within the limits of computing precision. We use convolutional perfectly matched layers as absorbing boundary conditions and practically demonstrate that they are well-suited for applications involving time-dependent media. Transmission of plain monochromatic waves through a time-dependent slab with the dielectric permittivity and magnetic permeability changing linearly with time, which has been investigated analytically in an earlier work, is studied numerically. Propagation of pulses with a finite continuous spectrum through the same system is studied both analytically and numerically. In all cases, the analytical and numerical results are in good agreement, which demonstrates that the code developed produces physically valid results. The technique developed is a powerful tool for designing new devices based on time-dependent metamaterials. We discuss one example of such an application, namely modelling a tunable wavelength-division multiplexer, as well as the prospects of designing other optical devices. <br /><br /> <div><strong>Graduate school:</strong> Physics<br /><strong>Main supervisor:</strong> Philippe Tassin</div> <div><strong>Examiner</strong>: Jari Kinaret</div> <strong>Opponent:</strong> Docent Istvan Pusztai, Subatomic and Plasma Physics, Department of Physics, Chalmers<br /><br /><br /> Cinema in Raven & Fox!<p>Raven and the Fox, multifunctional room, Forskarhuset Fysik, MC2</p><p>​​​​</p><br />Wednesday, 28 March, it is time for the third round of GPC's Science Cinema event.<br />This week we show two films about the plasticity of the brain by Max Cynader and Michael Merzenich.<br /><br /><span><em>Neuroplasticity, also known as brain plasticity and neural plasticity is the ability of the brain to change throughout an individual's life, e.g., brain activity associated with a given function can be transferred to a different location, the proportion of grey matter can change, and synapses may strengthen or weaken</em><br /><em>over time (Wikipedia).</em><span style="display:inline-block"></span></span><br /><span><span></span><span style="display:inline-block"></span><strong></strong></span><span><span></span><span><strong><br />Organiser:</strong> Neuroforum, Göteborg,<a href=""></a><br /><strong>Host:</strong> Professor Per-Olof Nilsson, Department of Physics, Chalmers<br /><br /></span></span><span><strong>Note:</strong> Limited number of seats (26) - show up in time to grab one!<span style="display:inline-block"></span></span><br /><br /><strong>Welcome!</strong> concert at Physics<p>Location: Physics Centre Personnel room, Origo building, 4th floor</p><p>Enjoy your Friday lunch accompanied by some live music.</p> Vahala, Caltech: Towards Integrated Optical Time Standards and Frequency Synthesizers<p>Kollektorn, lecture room, MC2-huset, MC2</p><p>Seminar with Professor Kerry Vahala, Ted and Ginger Jenkins Professor of Information Science and Technology and Professor of Applied Physics, California Institute of Technology (Caltech), USA,, ​Title: Towards Integrated Optical Time Standards and Frequency Synthesizers</p><h5 class="chalmersElement-H5">​ABSTRACT  </h5> <div>Communication systems leverage the respective strengths of optics and electronics to convey high-bandwidth signals over great distances.  These systems were enabled by a revolution in low-optical-loss dielectric fiber, complex integrated circuits as well as devices that link together the optical and electrical worlds.  Today, another revolution is leveraging the advantages of optics and electronics in new ways.  At its center is the laser frequency comb which provides a coherent link between these two worlds. Significantly, because the link is also bidirectional, performance attributes previously unique to electronics and optics can be shared. The end result has been transformative for time keeping, frequency metrology, precision spectroscopy, microwave-generation, ranging and other technologies. Even more recently, low-optical-loss dielectrics, now in the form of high-Q optical resonators, are enabling the miniaturization of frequency combs. These new `microcombs’ can be integrated with electronics and other optical components to potentially create systems on-a-chip.  I will briefly overview the history and elements of frequency combs as well as the physics of the new microcombs. Application of the microcombs for spectroscopy and LIDAR will be discussed.  Finally, efforts underway to develop integrated optical clocks and integrated optical frequency synthesizers using the microcomb element are described.</div> <div> </div> <h5 class="chalmersElement-H5">BIOGRAPHY</h5> Kerry Vahala studies the physics and applications of high-Q optical microcavities. His research group has pioneered resonators that hold the record for highest optical Q on a semiconductor chip and has also launched many of the research topics in the field of optical microcavities. Applications currently under study include micro-gyros with Earth-rotation-rate sensitivity and soliton micro-combs. Vahala was involved in the early effort to develop quantum-well lasers for optical communications and he received the IEEE Sarnoff Medal for his research on quantum-well laser dynamics. He has also received an Alexander von Humboldt Award for work on ultra-high-Q optical microcavities and is a fellow of the IEEE, the IEEE Photonics Society and the Optical Society of America. Vahala is the Jenkins Professor of Information Science and Technology and Professor of Applied Physics and received his B.S., M.S., and Ph.D. degrees from Caltech. He currently serves as the Executive Officer of the Department of Applied Physics and Materials Science and holds over 30 patents in photonics. <div><a href=""></a> </div> Mapar, Physics<p>Kollektorn, lecture room, MC2-huset, MC2</p><p>Title: Waveguide evanescent-field microscopy for label-free monitoring of biological nanoparticles: Fabrication, Characterization and Application</p>​<br /><strong>Sammanfattning:</strong> To be announced Bunch by Christophe Demazière<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​From Department of Physics, Chalmers</p> Physics Colloquium by Andreas Schnyder<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​From Max-Planck Institut, Stuttgart</p> dag - Vetenskapsfestivalen<p>Gustaf Dalén-salen, lecture hall, Gustaf Dalénsalen, Fysik</p><p>Fysikens dag är Fysikcentrums årliga bidrag på Vetenskapsfestivalens öppna program. Välkommen till en inspirerande temadag fullspäckad med intressanta föredrag. Du bjuds på en inblick i den senaste forskningen inom flera av fysikens områden och möjlighet att ställa dina kluriga frågor till våra forskare. Note that all the lectures will be held in Swedish.</p><h3 class="chalmersElement-H3">Program Saturday 21 April, 2018</h3> <span><strong>Moderators</strong><strong>:</strong> </span><span><span>Christian Forssén, Associate Professor and <span style="display:inline-block"> </span></span></span><span>Fredrik Höök, Professor at the Department of Physics, Chalmers.<span style="display:inline-block"></span></span><br /><strong></strong><p><strong><br />10.00 – 10.<span></span><span style="display:inline-block"></span>40 Gravitationsvågor från svarta hål</strong><span><br /></span><span><em>Ulf Gran, biträdande professor, Fysik, Chalmers</em><br /> </span><br /><strong>10.45 – 11.25 </strong><strong>När ögat inte räcker till</strong><strong><br /></strong><em>Cecilia Fager, doktorand, </em><span><span><em>Fysik, Chalmers</em><span style="display:inline-block"></span></span></span><br /><br /><span><strong>11.25 - 11.45 Fika<br /></strong>Fysikcentrum Göteborg bjuder alla besökare på fika i pausen.<span style="display:inline-block"></span></span><br /><br /><strong>11.45 – 12.25 </strong><span><strong>Vad väger en cell?</strong><br /><em>Daniel Midtvedt, forskare, Fysik, Chalmers</em><br /></span><br /><strong>14.00 – 14.40 Om konsten att sväva på en ljusstråle!</strong><br /><span></span><em>Dag Hanstorp, professor, Fysik, Göteborgs universitet</em><br /><br /><strong>14.45 – 15.25 </strong><span><span><strong>Hur kommunicerar biologiska celler med varandra</strong><strong>?  <br /></strong></span></span><span><span><em>Tatsiana Lobovkina, forskarassistent, Kemi, Chalmers</em><br /></span></span><br /><strong>15.<span></span><span style="display:inline-block"></span>30 – 16.10 Einsteinföreläsning<br /></strong>Enligt traditionen håller en hemlig gäst ett föredrag till minne av Albert Einsteins Nobelföreläsning i Göteborg.<br /></p> Noferini, Fysik<p>KA, lecture hall, Kemi, Campus Johanneberg</p><p>Title: Neutron scattering for sustainable energy materials: investigations of proton dynamics in acceptor doped barium zirconates.</p><strong> <br />Abstract:</strong> To be announced.<br /> Bunch by Dag Winkler<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​From Department of Michrotechnology and Nanoscience, Chalmers</p> Physics Colloquium by Nicholas Suntzeff<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​From Texas A&amp;M University.</p> Mystery of Water Revealed from X-ray Laser Studies<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>Colloquium by Anders Nilsson, Division of Chemical Physics, Department of Physics, Stockholm University, Sweden</p><h4 class="chalmersElement-H4"><br />Abstract:</h4> <div>Water is of extreme importance for our society and the key component of life as we know it but it is also of extraordinary interest due to its remarkable physical properties that differ from almost all other liquids. Deviation of water’s properties from a simple liquid exists already in the ambient temperature regime and then becomes strongly enhanced upon supercooling. In particular the finding that the thermodynamic response and correlation functions appear to diverge towards a singular temperature estimated by power-law fits of about 228 K has led to several hypotheses about the origin of waters anomalous properties. One hypothesis to explain the apparent divergence is that there exists a liquid-liquid transition with a liquid-liquid critical point at rather high positive pressures. In this scenario the Widom line, defined as the locus of correlation length maxima in the P-T plane, emanates from the critical point as a continuation of the liquid-liquid transition line into the one-phase region and the divergence in the response functions is towards this line. The challenge is that the temperature Ts lies below the homogeneous ice nucleation temperature 232 K, a region of the phase diagram that has been denoted as “no man’s land”, since ice crystallization occurs on much faster time scale compared to the experimentally accessible time scale in a typical laboratory setting.</div> <div>Here I will present how x-rays from x-ray lasers and synchrotron radiation sources can be used to probe the liquid in the deep supercooled water regime inside no-man’s land. In particular I will discuss if a liquid-liquid transition, Widom line and a critical point exists in deep supercooled water causing fluctuations all the way up to ambient temperature.</div> Bunch by Martin Andersson<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​From Department of Chemistry and Chemical Engineering, Chalmers.</p> Physics Colloquium: Compacted dimensions and singular plasmonic surfaces<p>PJ, lecture hall, Fysik Origo, Fysik</p><p>​Special Colloquium by Professor Sir John Pendry, Imperial College London, UK</p><h4 class="chalmersElement-H4">​Abstract:</h4> <div>In advanced field theories, there can be more than four dimensions to space, the excess dimensions described as compacted and unobservable on everyday length scales. We report a simple model, unconnected to field theory, for a compacted dimension realized in a metallic metasurface periodically structured in the form of a grating comprising a series of singularities. An extra dimension of the grating is hidden, and the surface plasmon excitations, though localized at the surface, are characterized by three wave vectors rather than the two of typical two-dimensional metal grating. We propose an experimental realization in a doped graphene layer.</div> Physics Colloquium by Constantino Tsallis<p>Kollektorn, lecture room, MC2-huset, MC2</p><p>From Brazilian Center for Research in Physics, Brazil</p> On dark matter<p>Kollektorn, lecture room, MC2-huset, MC2</p><p>This workshop will bring together theoretical and experimental physicists to identify optimal strategies for the analysis of next generation dark matter search experiments.</p><h4 class="chalmersElement-H4">Abstract:</h4> <div> Increasingly accurate astronomical and cosmological observations reveal that most of the matter in the Universe is non luminous, and made of an unknown substance called dark matter (DM). The nature of DM remains a mystery, but indirect evidence points towards a new hypothetical particle as the prime candidate. Although the DM particle has so far escaped detection, a new generation of experiments is or will soon start operating, reaching the sensitivity required by the state-of-the-art theories to discover the first non-gravitational signals of DM.</div> <div><span class="text-normal page-content"><div> </div> <div>The aim of this conference is to deliver optimised strategies for DM particle identification. This aim will be pursued by bringing together theoretical and experimental physicists in order to direct efforts jointly and wisely.</div> <div> </div> <div> </div> <div> </div> <div><strong>Topics to be covered in the conference include:</strong></div> <div> </div> <div>Status report on the experimental search for DM.</div> <div> </div> <div>DM phenomenology.</div> <div> </div> <div>DM theory.</div> <div> </div> <div>Complementarity of different DM detection strategies and global statistical analyses.</div> <div> </div> <div>Astrophysical and nuclear physics inputs.</div></span></div> seminar on Electromobility<p>Palmstedtsalen, university building, Palmstedtsalen, Campus Johanneberg</p><p>​Welcome to an Initiative seminar on Electromobility, arranged by Areas of Advance Transport and Energy.</p><span class="text-normal page-content"> <strong>What role will electric vehicles play in the future, for how we plan our cities, for our economy, our health and for the environment?</strong><br /><br />Having been around for more than a century, electric vehicles are now coming into use on a scale that may have major implications  on travel and transportation - by air, by water and by land.  Areas of Advance Transport and Energy are happy to welcome you to a full day at Chalmers, where we discuss different aspects on electromobility.<br /><br /><strong>WHEN</strong>: 13 September 2018<br /><strong>WHERE</strong>: Palmstedssalen, Chalmersplatsen 1, Göteborg<br /><em>The seminar will be in English.</em><br /><br /><strong>SESSIONS</strong><br /><ul><li>Visions for the future</li> <li>Liveable cities</li> <li>Policies, regulations and driving forces</li> <li>Technology aspects on electromobility</li></ul> <br />Registration is open! <br /><a href="">REGISTER &gt;&gt;</a><br /><br /><br />More information will be published on the </span><a href=""><span class="text-normal page-content">seminar web page &gt;&gt;</span></a><br /> Sustainability Day 2018<p>TBA, Chalmers Johanneberg and Lindholmen</p><p>​Chalmers Sustainability Day is back - Tuesday 23 October 2018. This year’s theme is Good Health and Well-being.</p>​ <br />More information will follow, stay updated through the event webpage: <a href="/en/about-chalmers/Chalmers-for-a-sustainable-future/sustainability-day2018/Pages/default.aspx">Chalmers Sustainability Day 2018</a><br /><br />For now, save the date!