College of Arts and Sciences

Topological defects in nematic liquid crystals: playground of fundamental physics

Samo Kralj

1Faculty of Natural Sciences and Mathematics, University of Maribor, Maribor, Slovenia

2Solid State Department, “Jožef Stefan” Institute, Jamova 39, Ljubljana, Slovenia

       Topological defects (TDs) are an unavoidable consequence of continuous symmetry breaking phase transitions [1]. They appear at all scales of physical systems, including particle physics, condensed matter and cosmology. Due to their topological origin they display several universalities that are independent of the systems’ microscopic details.

Continue reading… Samo Kralj,Josef Stefan Institute in Ljubljana and University of Maribor, Slovenia, Topological defects in nematic liquid crystals: playground of fundamental physics

High entropy alloys: mechanical properties and phase stability
Maryam Ghazisaeidi, Department of Materials Science and Engineering, Ohio State University

The term “High entropy” alloys (HEA) refers to a relatively new class of multicomponent—usually
five or more—metallic alloys in equal or near equal atomic concentrations. Instead of ordered
intermetallics, expected from classical physical metallurgy, some HEA systems strikingly crystalize
as single phase solid solutions with simple crystal structures. The complex compositions of these
alloys, and their derivatives, lead to unique properties. They also encourage new ways of viewing
fundamentals of physical metallurgy,

Continue reading… Maryam Ghazisaeidi, Ohio State University, High entropy alloys: mechanical properties and phase stability

Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity

Joe Trodahl

 MacDiarmid Institute for Advanced Materials and Nanotechnology

Victoria University of Wellington New Zealand

Controlling the flow of electronic spin in addition to the charge promises speed and power demand advantages. However, there are as yet few “spintronic” devices on the market, in part due to a lack of intrinsic ferromagnetic semiconductors that would permit full exploitation of the coupled spin/charge technology. To date the only full series of such materials are the mononitrides of the lanthanides, the 14 rare-earth elements.

Continue reading… Joe Trodahl, Victoria University of Wellington, Rare-earth nitrides; semiconductors, spin/orbit magnetism, tunnelling MRAM, superconductivity

3D plasmonic nanostructures for biology and medicine

Francesco De Angelis

Istituto Italiano di Tecnologia, Genoa, Italy

In this talk we will show our last achievements and future perspectives of distinct class of plasmonic devices devoted to biological and medical applications. Among them, we will introduce the concept of meta-electrodes, namely a nanostructured surface that can work as electrode, a broad band plasmonic antenna, and optimal cellular interface (see Figure 1). We show that meta-electrodes combined with commercial CMOS technology enable high quality intracellular electrical signals on the large network scale of human neuron and cardiomyocytes .

Continue reading… F. De Angelis, Istituto Italiano di Tecnologia, Genoa, Italy, 3D plasmonic nanostructures for biology and medicine

Quantum Magnonics in V[TCNE]2

The study of quantum coherent magnonic interactions relies implicitly on the ability to excite and exploit long lived spin wave excitations in a magnetic material. That requirement has led to the nearly universal reliance on yittrium iron garnet (YIG), which for half a century has reigned as the unchallenged leader in high-Q, low loss magnetic resonance, and more recently in the exploration of coherent quantum coupling between magnonic and spin [1] or superconducting [2] degrees of freedom. Surprisingly, the organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]2) has recently emerged as a compelling alternative to YIG.

Continue reading… Ezekiel Johnston-Halperin, The Ohio State University, Quantum Magnonics in V[TCNE]2

Conserving Helium: A story of MgB2 superconducting wire and MRI magnets

The fabrication of MgB2 superconducting wire has enabled the development of novel magnet designs for MRI systems. Compared to MRI magnets in use today, which are submerged in a bath of liquid helium, the higher critical temperature (39K) of the MgB2 facilitates conduction cooling which reduces the use of liquid helium by a factor of 100 or more. In collaboration with Hyper Tech Research, a world leader in the manufacture of MgB2 wire, and the Center for Superconducting and Magnetic Materials at the Ohio State University,

Continue reading… Mike Martens (CWRU Physics)

Sergey Kravchenko,

Northeastern University

The latest developments in the field of the metal-insulator transition in 2D

Abstract:
Ignited by the discovery of the metal-insulator transition, the behavior of low-disorder two-dimensional (2D) electron systems is currently the focus of a great deal of attention. In the strongly-interacting limit, electrons are expected to crystallize into a quantum Wigner crystal (Wigner, 1934), but no definitive evidence for this effect has been obtained despite much experimental effort over the years. Now we have found two-threshold voltage-current characteristics with a dramatic increase in noise between the two threshold voltages.

Continue reading… Sergey Kravchenko, Northeastern University, The latest developments in the field of the metal-insulator transition in 2D

Michelson Postdoctoral Prize Lecture 1

Astrophysical Signatures of Dark Matter Accumulation in Neutron Stars

Over the past few decades, terrestrial experiments have placed increasingly strong limits on the dark matter-nucleon scattering cross-section. However, a significant portion of the standard dark matter parameter space remains beyond our reach. Due to their extreme density and huge gravitational fields, neutron stars stand as optimal targets to probe dark matter-nucleon interactions. For example, over the last few years, the mere existence of Gyr-age neutron stars has placed strong limits on models of asymmetric dark matter. In this talk,

Continue reading… Tim Linden (Ohio State University)

 DNA folding thermo/dynamics with a twist

Alkan Kabakcioglu, Koc University, Istanbul

DNA denaturation is possibly one of the earliest problems in biophysics that grabbed the attention of statistical physicists. The nature of the folding/melting transition has been subject to debate since 60’s until a breakthrough in the past decade mostly settled the question. We recently readdressed the problem for circular DNA (which has a topologically imposed, fixed linking number due to helicity) and found that the melting behavior is qualitatively different from that of the unconstrained DNA with freely dangling ends.

Continue reading… Alkan Kabakcioglu, Koc University, DNA folding thermo/dynamics with a twist

Continue reading… no seminar/faculty meeting