Vorfundur Eðlisfræðifélags Íslands 22 Maí 2019

Verður haldin í Stofu HT-105 Miðvikudaginn 22 Maí í Háskólatorgi Háskóla Íslands frá kl 13:00 til 17:20. HT-105 er að finna í kjallara Háskólatorgs nálægt Stúdentakjallaranum.

Dagskrá vorfundarins byggist á Rannsóknaverkefnum sem Rannsóknamiðstöð Íslands hefur styrkt á undanförnum árum í Eðlisfræði. Erindin munu kynna rannsóknaverkefnin stuttlega ásamt að kynna eðlisfræðina með einföldum hætti. Ráðgert er að halda sambærilegan fund að hausti komanda. Fundurinn er opinn fyrir félagsmeðlimi og fólk með áhuga á eðlisfræði.

Spring meeting of the Icelandic Physical society will be conducted in Lecture hall HT-105 Wednesday 22 May at Háskólatorg University of Iceland from 13:00 to 17:20. HT-105 can be found in Háskólatorg close to the Studentcellar

The program is based on projects funded by Icelandic Research center during the last years. The talks will describe the projects shortly and the research field in simple terms. The Meeting is open to members and people interested in physics in general.

Tími Fyrirlesari Erindi
13:00-13:40 Jesus Zavala Franco Is gravity the only dark matter interaction that matters in the physics of galaxies
13:40-14:20 Lárus Thorlacius Heilmyndun í þyngdarskammtafræði og skammtasviðsfræði
14:20-15:00 Andrei Manolescu Excitons in core-shell nanowires with polygonal cross section
15:00-15:20 Kaffihlé
15:20-16:00 Margherita Zuppardo Thermoelectricity and quantum correlations in molecular junctions
16:00-16:40 Einar Örn Sveinbjörnsson Torleiðandi efni til notkunar í rafsviðssmárum gerðum í kísilkarbíði
16:40-17:20 Sveinn Ólafsson Rydberg fasi vetnis
17:20-18:00 Allir Free discussions in Stúdentakjallarinn

Fyrir kaffihlé

Jesús Zavala Franco

Is gravity the only dark matter interaction that matters in the physics of galaxies?

Abstract: The standard model of cosmic structure formation is based on the Cold Dark Matter (CDM) hypothesis where non-gravitational dark matter interactions are irrelevant for the formation and evolution of galaxies. Surprisingly, current observations allow for significant departures from the CDM hypothesis, which could potentially leave signatures of the dark matter particle nature in the properties of galaxies. In this talk, I will describe some of these 'alternative' dark matter hypotheses and their connection to particle physics models from the perspective of a generalized theory of structure formation.

Lárus Thorlacius

Heilmyndun í þyngdarskammtafræði og skammtasviðsfræði

Holographic approach to quantum gravity and strongly coupled quantum field theory

Abstract: Holographic duality, also referred to as the gauge theory/gravity correspondence, provides novel tools for the study of strongly coupled physical systems. These methods and ideas, which originally came from string theory, have been used to translate difficult theoretical problems in particle physics and condensed matter physics into more tractable problems in gravitational theory. On the other hand, by going to weak coupling on the quantum field theory side, holographic duality provides a working definition of quantum gravity via gauge theory dynamics and can be used to address fundamental questions about gravity in an interesting parameter range where standard notions of space and time cease to apply.

Andrei Manolescu

Excitons in core-shell nanowires with polygonal cross section

Abstract: We describe the formation of excitons in a tubular prismatic geometry representing the outer layer of a core-shell nanowire. We use a numerical approach based on a multi-electron Hamiltonian, with valence and conduction bands, which includes the Coulomb interaction. We focus on the implications of the quantum localization in the corners or on the sides of the polygonal cross section. We compare the results of the multi-electron method with those of an electron-hole model and we show that the latter does not reproduce all exciton energies. Our models explain recent experimental photoluminescence spectra obtained on asymmetric hexagonal shells.

Eftir kaffihlé

Einar Örn Sveinbjörnsson

Torleiðandi efni til notkunar í rafsviðssmárum gerðum í kísilkarbíði

Gate dielectric applicable to SiC MOSFETs for power electronics

Abstract: The Silicon Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is probably the most important electronic device yet made by humans. Such devices are pre-requisite for all commercial computers on the planet and are key elements in electric power transmission as well. The success of Si MOS technology relies on understanding the physics behind the device operation and the advancement of this technology is very strongly attached to research in condensed matter physics. Approximately 96% of all electronics today are made in silicon. Although silicon devices are reaching their performance limits due to quantum mechanical effects there is no given material that can replace silicon in circuits. However, there are some applications where other semiconductors can outperform silicon devices. One such area is high power electronics where silicon carbide is slowly but surely replacing silicon in such circuits. These devices provide higher switching speed and lower switching losses compared to its Si counterparts and are now competitive for blocking voltages above 900 V. However, the high volume market is in devices blocking 400-900 V. Currently, such devices made in SiC are not competitive due to poor electron channel mobility in SiC MOSFETs which is related to severe electron trapping in interface states between the SiC and the gate dielectric (SiO2). Methods have been developed that reduce the interface density to some extent which enabled commercialization of the high voltage (> 900 V) MOSFET. The goal of this research work is to improve the gate dielectric/SiC interface even further and significantly increase the electron channel mobility in SiC MOSFETs and thereby enabling devices for use in the 400-600 V range. This will be accomplished by replacing the currently used SiO2/SiC interface with an thin interface layer of AlN or Al2O3. Preliminary studies are promising and do show that it is possible to obtain both AlN/SiC and Al2O3/SiC interfaces with low density of interface states.

Margherita Zuppardo

Thermoelectricity and quantum correlations in molecular junctions

In this talk, I will introduce the main objectives, methodology amd present state of my current Rannís project. The goal of this project is to study with theoretical methods the effects of internal quantum correlations on thermoelectric transport, using as our main reference model a molecular junction. Quantum correlations (quantum discord and entanglement) are recognised to represent a valuable resource for quantum technologies i.e. for sensing, computing, and communication. On the other hand, their role in the performance and manipulation of energy-exchanging processes occurring at the nanoscale is yet to be understood. Such an understanding will be crucial to shed light on the way quantum features influence the energy properties of building blocks for the upcoming quantum technologies.

We chose investigate such effects in a particular class of n artificial nanostructures known as molecular junctions. These are made of a molecule, connected to two electrodes. Inside the molecule, two distinguishable quantum species are present: electrons and phonons generated by the vibrations of the nuclei. These two species interact strongly with each other at the quantum mechanical level. Under suitable operating conditions, such interaction will generate mutual quantum correlations. In the presence of a temperature difference, such systems can be seen as thermal machines, able to convert heat into electric current (thermoelectric effect). Electrons and phonons will both contribute to the thermoelectric transport between the leads: they both carry heat, but only electrons can carry electric charge, and the efficiency of this energy conversion is likely to be affected by quantum correlations between the two species. For these reasons molecular junctions are paradigmatic systems to analyze the interplay between quantum correlations and quantum transport phenomena.

Sveinn Ólafsson

Rydberg fasi vetnis

Rydberg Hydrogen Matter

Abstract: Among the atoms of the periodic system, Hydrogen and Deuterons have the lowest number of electrons and thus the simplest electronic structure and are generally only found in the simplest state as chemical binding of two atoms forming H2 and D2 molecules. Recently this picture started to be changed and questioned with work of Leif Holmlid at Gothenburg University Sweden. He was able first to form new cluster state K7 and K19 of K atoms who found stable state when the K atoms were assembled in an excited Rydberg state with high n excitation number. Later he was able to find methods to do the same thing for H and D and form Rydberg matter of H7 and H19. Further research work by him lead him to find a new transformed state he called Ultra-High-Density state (UHD) in which he observed 2.3 pm inter-proton pair distance with time of flight measurements technique. A distance that is about 30 times shorter than H2 molecule distance of 72 pm.[1] His latest published work states now that a relative weak laser pulse when it hits the UHD phase can cause part of the Hydrogen phase to disintegrate into subatomic particles like mesons and leptons travelling at high speed 0.1c-0.9c. Results that suggest baryon number violation if they are viewed from a single particle or two-particle interaction picture. Viewed as multi-particle condensation breakup the baryon number counting or violation is experimentally hard to perform without having very advanced 4π detector setup. Needless to say, most of Leif findings have been meet with wide disbelief. Ten years after his first publication of UHD, as a first research group to try to replicate his work, we present the first experimental results that give the same results. Something extraordinary is occurring in our experiments and it needs to be studied and checked further with more advance methods in order to give the final conclusion on the validity of Holmlid´s work and interpretation.

1. Ultra dense protium p(0) and deuterium D(0) and their relation to ordinary Rydberg matter: a review Phys. Scr. 94 (2019) 075005 (26pp) https://doi.org/10.1088/1402-4896/ab1276

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