Physics Friday Colloquia

- Spring 2014

Department of Physics organizes a series of colloquia. Friday's colloquium is open to everyone. It will be served tea/coffee and biscuits from 14:00. Talk starts at 14:15.

This year we have tried to put together a broad program of great speakers, so we do hope that you will join us regularly throughout this semester. Topics will include organic electronics, nanoscience, life sciences and biophysics, antarctic atmospheric physics and more besides. Speakers have been firmly encouraged to make their talks accessible to non-experts - so we hope that you'll find all of the colloquia interesting.

Coordinator: Arne Brataas

Friday colloquium 2014

January 24

Velimir Radmilović, Nanotechnology and Functional Materials Center, Faculty of Technology and Metallurgy, University of Belgrade, Serbia
«Functional Oxide Thermoelectrics: The Case of ZnO Nanowires»

January 24

Velimir Radmilović, Nanotechnology and Functional Materials Center, Faculty of Technology and Metallurgy, University of Belgrade, Serbia
«Functional Oxide Thermoelectrics: The Case of ZnO Nanowires»

Abstract

Functional oxides for thermoelectric applications

Civilization is facing to develop alternative renewable energy sources, because of the limited fissile fuels and their impact on the environment. Functional oxide nanowires are expected to play an important role in scavenging waste heat and converting it into electricity. Some complex superlattices in nanostructures contain periodic compositional and structural features, typically on the nanometer scale, making them promising materials for thermoelectric applications. In this presentation, I will discuss our recently discovered a novel method to produce M2O3(ZnO)n polytypoid nanowires (M=In, Ga, Fe,..) by a facile solid state diffusion process. This is in agreement with the theoretical prediction that it is possible to increase the material-dependent figure of merit, zT, by using low dimensional materials, attributed to electronic band structure changes and enhanced interface phonon scattering. Atomic resolution HAADF imaging is used to perform a detailed structural analysis on the M2O3(ZnO)n  nanowires, unambiguously determined the location of indium within the structure and to evaluate lattice strain and the presence of defects. Based on this analysis we propose that the superlattice structure is generated through a defect-assisted process. One of the greatest advantages of this novel synthesis is the ability to tune the nanoscale features of the polytypoid wires by simply adjusting the amount of metal precursor. We also performed a quantitative analysis of the change in superlattice inclusion density and periodicity with metal deposition. Compare to ZnO nanowires, these new oxide thermoelectric nanostructures exhibited almost three orders of magnitude increase in efficiency. This will enable future studies on structure-dependent thermoelectric properties and possibly lead to further enhancements in thermoelectric efficiency.

Abstract by Velimir Radmilović

Functional Oxide Thermoelectrics: The Case of ZnO Nanowires  [pdf] 65KB

This first colloquia will take place in D4-132

Wed, 12 Feb 2014 17:12:42 +0100

February 7

Hans Grelland, Universitetet i Agder
«Kan vi forstå fysikken? P.A.M. Dirac, Ludwig Wittgenstein og kvantefysikkens tolkningsproblem»

February 7

Hans Grelland, Universitetet i Agder
«Kan vi forstå fysikken? P.A.M. Dirac, Ludwig Wittgenstein og kvantefysikkens tolkningsproblem»

Abstract

Kan vi forstå fysikken? P.A.M. Dirac, Ludwig Wittgenstein og kvantefysikkens tolkningsproblem

I klassisk fysikk forståes det matematiske språket (symboler og likninger) som representasjon av en virkelighet vi kan forestille oss og som er beslektet med vanlige menneskelige erfaringer. I kvantefysikken, og dermed i all moderne fysikk, har vi et meget presist matematisk språk som kan brukes til å bygge modeller og gjøre beregninger, men det matematiske språket svarer ikke lenger til en virkelighet vi kan forestille oss. Spørsmålet er: kan vi likevel forstå dette matematiske språket og dermed den fysikken det representerer? Hva er det i så fall å forstå, og hvordan kan forståelse oppnås? Målet må være at fysikken ikke bare skal gi oss gode verktøy for beregning, men også gi en forståelse av den fysiske verden utenfor oss. P. A. M. Dirac, som var en av de tre som fikk Nobelprisen for å utvikle kvantemekanikken, var kjent for ikke å ville si noe om teoriens tolkningsproblem, men han er samtidig kjent for å ha utviklet den symbolske metode og skrevet den klareste fremstillingen av teorien i sin berømte lærebok Principles of Quantum Mechanics. Jeg vil argumentere for at Dirac i sin tenkning gir oss nøkkelen til hvordan vi kan forstå kvantemekanikken, en tenkning som er nært beslektet med Ludwig Wittgensteins filosofi om språk i hans verk Tractatus Logico-Philosophicus.

Anbefalt litteratur

  1. Helge S. Kragh:  DIRAC: A Scientific Biography. Cambridge University Press 1990.
  2. Graham Farmelo: The Strangest Man. The Hidden Life of Paul Dirac, Quantum Genius. London: Faber & Faber 2009.
  3. P.A.M. Dirac: Principles of Quantum Mechanics. Oxford University Press. 1st edition 1930, 4th edition 1958, fortsatt I opptrykk.
  4. Ludwig Wittgenstein: Tractatus Logico-Philosophicus. Norsk oversettelse ved Terje Ødegaard. Gyldendal 1999.
  5. Allan Janik og Stephen Toulmin: Wittgenstein's Vienna. Chicago: Ivan R. Dee 1996.

February 14

Harald Buch Steen, Radiumhospitalet, Oslo University Hospital
Erik Pettersen, Department of Physics, University of Oslo (UiO)
«The development of flow cytometry and it suse in cell kinetics studies»

February 14

Harald Buch Steen, Radiumhospitalet, Oslo University Hospital
Erik Pettersen, Department of Physics, University of Oslo (UiO)
«The development of flow cytometry and it suse in cell kinetics studies»

Abstract

The development of flow cytometry and it suse in cell kinetics studies

Flow cytometry is a quantitative method measuring fluorescence intensity from cells on a single cell basis. Cells can be stained with several fluorescent dyes and the fluorescence intensity measured simultaneous from each individual cells and correlated. This technique is a powerful tool to study various aspects of cells.

Cancer is due to uncontrolled proliferation of cells and it is of importance to understand the mechanisms of cell division and how a cell behaves in the various phases of its life. Flow cytrometry is very useful in this respect.

Tore built the first flow cytometer at the Radiumhospital and later he and Harald Steen developed a microscope based version of a flow cytometer. Together with Erik Pettersen, Tore used his flow cytometer to learn more about cell kinetics and to study the effect of radiosensitizer on hypoxic cells which are extremely resistant to ionizing radiation. Today flow cytometers are commercial available and at Dept. of Physics we have a flow cytometer equipped with 4 lasers and 10 detectors, making it possible to quantitate several cellular parameters simultaneously.

The colloquium will take place in R10

Wed, 12 Feb 2014 17:07:27 +0100

February 21

Martin Landrø, Petroleum engineering and applied geophysics (NTNU)
«Cavity formation and seismics»

February 21

Martin Landrø, Petroleum engineering and applied geophysics (NTNU)
«Cavity formation and seismics»

Abstract

Cavity formation and seismics

Lord Rayleigh was among the first to study the collapse of a cavity in water in 1917. Since then, both experimental and theoretical cavity studies have been performed. In the seismic industry, cavitation has been exploited to generate acoustic signals using water guns. By forming high velocity water jets, cavities are formed and when they collapse they generate a strong acoustic signal. Today the most common marine seismic source is the air gun, and then the acoustic energy is created directly by the air bubble. In recent years, it has been found that also air gun sources generate some cavitation, and this will be the key topic for this presentation. What are the major physical mechanisms causing this cavitation and is it possible to reduce this noise? Cavitation noise is high frequent, often up to 60-100 kHz, and since this is the same frequency range as some whales use for communication we want to make sure that this amount of noise is as low as possible.


February 28

Alex Hansen, Department of Physics, NTNU
«Scientific publishing: The open access revolution»

February 28

Alex Hansen, Department of Physics, NTNU
«Scientific publishing: The open access revolution»

Abstract

Scientific Publishing: The Open Access Revolution

There were 116000 papers on physics published in 2010. Scientific publishing is a huge industry that up to now has operated essentially in the same way since the mid seventeenth century. This modus operandi no longer matches the information technology which has emerged over the last twenty years. When journals were made of paper, nobody reacted to the journals ending up owning the copyright to the papers they published. Today, when papers mainly exist as electronically stored files, the following question is asked: The public pays for the research, for the writing of the papers, for their assessment through peer review. The journals then sell the work back to the researchers for a huge profit.  Is this right?  The answer that has emerged is "open access publishing". This means that papers are not hidden by subscription walls but freely accessible.  This, however, demands that the authors pay to get their work published.  Not everybody thinks that this is great idea, and the stage is set for controversy. 

I will in this talk paint a picture of today's scientific publishing landscape. I will discuss where peer review is heading, plagiarism, predatory publishers, green and gold open access, impact factor... i.e. the essential concepts that one needs to orient oneself in this highly complex and shifting landscape. I will spice the story with a number of interesting case stories.


Thu, 27 Feb 2014 09:23:11 +0100

March 14

Jens Højgaard Jensen, Institut for Natur, Systemer og Modeller (IMFUFA), Roskilde Universitet (RUC)
«Teaching students to think as physicists using unformalized problems»

March 14

Jens Højgaard Jensen, Institut for Natur, Systemer og Modeller (IMFUFA), Roskilde Universitet (RUC)
«Teaching students to think as physicists using unformalized problems»

Abstract

Teaching students to think as physicists using unformalized problems

Since the foundation of Roskilde University 40 years ago a physics course focused on solving unformalized problems has been a corner stone for our students studying physics. The course differs substantially from most other university physics courses focusing more on teaching skills and ways of perception than syllabus.

In the seminar I will explain:

  1. what is meant by "think as physicists"
  2. what is meant by "unformalized problems"
  3. how the course is organized
  4. what we have experienced running the course

Wed, 12 Mar 2014 09:14:51 +0100

March 21

Poul Henrik Damgaard, Niels Bohr Institute, Copenhagen University
«Baryon Asymmetry of the Universe»

March 21

Poul Henrik Damgaard, Niels Bohr Institute, Copenhagen University
«Baryon Asymmetry of the Universe»

Abstract

Baryon Asymmetry of the Universe

Why is the Universe composed of baryons and not a mixture of baryons and anti-baryons?

The Standard Model of particle physics has all ingredients for explaining this puzzling baryon asymmetry. However, already earlier experimental bounds on the Higgs mass showed that this explanation was ruled out, and with the Higgs discovery at the LHC this is now firmly established.

In this talk I will give a simple introduction to the subject and show how the requirement of baryon asymmetry gives very tight constraints on physics beyond the Standard Model. I will show that already now data from the LHC at CERN are very restrictive. With the start of new runs at the LHC from 2015 this may essentially rule out such a scenario altogether -- or confirm it.


Thu, 13 Mar 2014 12:01:26 +0100

March 28

Subir Sarkar, Niels Bohr Institute & Particle Theory Group, University of Oxford
«Connecting inner space & outer space»

March 28

Subir Sarkar, Niels Bohr Institute & Particle Theory Group, University of Oxford
«Connecting inner space & outer space»

Abstract

Connecting inner space & outer space

We have just celebrated the centenary of the finding that the Earth is constantly bombarded by high energy `cosmic rays' from outer space. This initiated a glorious era of discovery of many new elementary particles (positron, muon, pion, ...) and developed into accelerator-based research in high energy physics. A century later this has given us the triumphant `Standard Model' of particle physics which provides a precise quantum description of all fundamental processes in terrestrial laboratories, including (with the recent discovery of "a Higgs boson") an understanding of how particles acquire mass. Unfortunately the Standard Model does not explain any of the salient features of the universe as a whole - Why there is matter but no antimatter? Why there is so much more `dark matter' of unknown origin? Why is the expansion rate apparently accelerating, as if driven by a Cosmological Constant-like, dominant component of `dark energy'? I will describe how new experiments and theoretical developments at the rapidly growing interface of astro-particle physics are attempting to answer these cosmic questions, by linking them to possible new physics beyond the Standard Model.


Fri, 21 Mar 2014 09:02:49 +0100

April 4

Charles Marcus, Niels Bohr Institute, University of Copenhagen
«Center for Quantum Devices»

April 4

Charles Marcus, Niels Bohr Institute, University of Copenhagen
«Center for Quantum Devices»

Abstract

Center for Quantum Devices

This talk will introduce the Center for Quantum Devices at University of Copenhagen, a basic research center established in 2012, comprising theoretical and experimental condensed matter physics, quantum information, and materials science.

The talk will focus on two projects in greater detail: spin qubits for quantum information processing, and semiconductor-superconductor structures that support majorana fermions.


Fri, 04 Apr 2014 10:42:23 +0200

April 11

Ron Jansen, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
«Silicon Spintronics»

April 11

Ron Jansen, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan
«Silicon Spintronics»

Abstract

Silicon Spintronics

Ron Jansen (2014 IEEE Magnetics Society Distinguished Lecturer). National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan

Worldwide efforts are underway to create a revolutionary and energy-efficient information technology in which digital data is represented by the spin orientation of electrons. Implementing spin functionality in silicon, the mainstream semiconductor, has the potential to create broad impact. Remarkable advances in the creation and control of spin polarization in silicon have therefore generated much excitement. This lecture provides a transparent picture of silicon spintronics, including the key developments and achievements, our current understanding, as well as the unsolved puzzles and challenges that stimulate researchers in the field.

First, the basic idea of spin-based information technology and silicon spintronics is introduced. Ferromagnets have non-volatile memory functionality, whereas semiconductors provide amplification and transistor action. What if we integrate ferromagnets and silicon — magnetic memory and logic computing? Then the main building blocks are described: one needs to be able to create spin polarization in the silicon, to manipulate it, and thereafter detect the spins. The generation of a spin flow by electrical means (driven by a bias voltage) or thermal means (driven by a heat flow) are discussed. Ferromagnetic tunnel contacts are shown to provide a robust method to do this, at room temperature. The lecture concludes with a prospect on future developments, which certainly includes more surprises as silicon spintronics comes of age.

  1. R. Jansen, Silicon spintronics, Nature Materials 11, 400-408 (2012).
  2. J.C. Le Breton, S. Sharma, H. Saito, S. Yuasa and R. Jansen, Thermal spin current from a ferromagnet to silicon by Seebeck spin tunnelling, Nature 475, 82-85 (2011).
  3. S.P. Dash, S. Sharma, R.S. Patel, M.P. de Jong and R. Jansen, Electrical creation of spin polarization in silicon at room temperature, Nature 462, 491-494 (2009).

Biography

Dr. Ron Jansen received a PhD in Experimental Physics from the University of Nijmegen (The Netherlands) in 1997, and was a postdoctoral associate at the Massachusetts Institute of Technology (MIT, Cambridge, USA). After that he moved to the University of Twente (The Netherlands), where he became a tenured assistant professor, associate professor, leader of the NanoElectronics Research Chair and group leader with the Netherlands Foundation for Fundamental Research on Matter (FOM). Since 2010, he works at the National Institute of Advanced Industrial Science and Technology (AIST, Tsukuba, Japan), where he is now a prime senior researcher (首席研究員) at the Spintronics Research Center.

He has published 100+ technical articles in peer-reviewed journals, incl. book chapters and reviews, and given more than 110+ invited scientific presentations. He received personal award grants from the Royal Netherlands Academy of Arts and Sciences and from the Netherlands Organization for Scientific Research, and is IEEE Magnetics Society Distinguished Lecturer for 2014. He served on international advisory boards and program committees of various international conferences in magnetism, semiconductor devices and spintronics. He was editor of IEEE Transactions on Magnetics and the European Journal of Applied Physics and is a member of the IEEE Magnetics Society.

Silicon Spintronics [pdf]


Mon, 24 Mar 2014 09:18:45 +0100

May 12

Robert L. Byer, Department of Applied Physics, Stanford University
«Laser Acceleration on a Chip»

The Friday Colloquium takes place on a MONDAY (ordinary time and place)

May 12

Robert L. Byer, Department of Applied Physics, Stanford University
«Laser Acceleration on a Chip»

The Friday Colloquium takes place on a MONDAY (ordinary time and place)

Abstract

Laser acceleration on a chip

Recent experimental success has demonstrated the potential for laser driven accelerators in dielectric structures with greater than 300MeV/m acceleration gradient.  Progress and future directions in laser acceleration will be discussed.  Accelerators on a chip open a pathway to coherent x-ray sources and to physics at the TeV energy scale.



Wed, 15 Jan 2014 11:50:32 +0100

Contact information

Coordinator Physics Friday Colloquia

Arne Brataas
Arne Brataas
E-mail: arne.brataas@ntnu.no

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