# Seminar Tuesday June 16 – Dan Zawada

Location: Physics 175
Time: 3:30 June 16 2015

Abstract: Ozone is an important trace gas in the atmosphere.   The ozone layer is responsible for the temperature inversion in the stratosphere, and attenuates UV radiation at the Earth’s surface.  Furthermore, ozone in the troposphere is a pollutant and is frequently monitored to make air quality predictions.   One method of measuring ozone is remote sensing using limb scattered sunlight.  Currently this technique relies on the assumption that the atmosphere is locally horizontally uniform, i.e. that ozone concentration varies only as a function of altitude.  This assumption breaks down in areas where there is a large horizontal gradient, for example, at the edge of the ozone hole or near the tropopause where small scale processes are prevalent. Future instruments will have higher sampling rates, which may make it possible to use tomographic techniques to retrieve ozone in more than one dimension simultaneously. In this talk I will briefly outline different methods of remote sensing ozone in the atmosphere with UV/visible radiation, and present some of my research related to ozone tomography.

# Seminar Tuesday June 9 – Akbar Rohollahi

Speaker: Akbar Rohollahi
Location: Physics 175
Time: 3:30 June 09 2015

Abstract: Delivering fuel to the core of the tokamak fusion plasma to keep it in steady state mode and optimize energy confinement has meaningful importance in fusion technology. Several fueling methods such as edge gas puffing, pellet injection and compact toroid injection (CT) have been proposed. Among them, the CT is one of the most efficient methods for the core fuelling of large tokamak fusion reactors in the future. . The CT can deposit the fuel in the full controlled manner at the any depth of tokamak plasma. The CT is a self-contained high density plasmoid with an axial symmetry and a stalwart poloidal and toroidal magnetic field. To maximize the bootstrap current fraction, density and pressure profile optimizations are essential in tokamak reactors. Therefore deposition of a small amount of fuel in a desired location is required. These criteria could be achieved by using CT.   In addition to fueling usage, CT would inject a toroidal momentum into tokamak plasma. So the CT might provide additional tools to control plasma flows and rotation that could be effective in plasma confinement.

In this seminar I’ll briefly talk about STOR-M tokamak and after that I will provide you some information about the CT and recent development in the fueling technics of tokamak reactors.

# Seminar Tuesday June 2nd – Sarah Purdy

Speaker: Sarah Purdy
Location: Physics 175
Time: 3:30 June 02 2015

An open discussion on jobs in Physics

Abstract: Many of us are looking for work or will be looking for work within the
next 2 years.  Some of us are wondering what we’re doing getting a
degree in Physics. In this session I will discuss job trends in the
field of Physics including unemployment rate of 0% for MSc in Physics,
what income can be expected and other statistics.

While I have done some research on the job climate, I myself am
searching for work. I’ll present some tips and preparation strategies
that I’ve learned for applications and interviews. I’d like to invite
other students to share their views and experiences in an open format.

# Seminar Tuesday May 19 – Neil Johnson

Speaker: Neil Johnson
Location: Physics 127
Time: 3:30 May 19 2015

Abstract: Graphene is one of the most celebrated and intensively studied materials of the last decade. Its potential uses include transparent conductors, filtration, optoelectronics, photovoltaics and as a semiconductor for electronic devices. However, its implementation as a semiconductor is hampered by its utter refusal to stop conducting, even in the absence of an external field or doping. This has a deleterious effect on the ON/OFF ratios of graphene-based devices, and as such none have ever been made that are able to outperform current bulk silicon devices.

Silicene, the silicon-based analogue to graphene, is expected to have a number of significant advantages over its carbon-based cousin. It should have a tuneable bandgap, an ambipolar field effect and possibly even spin-polarization all from the application of an external gating voltage. Clearly, silicene is much, much better than graphene could ever hope to be. However, one slight, minor stumbling block in the implementation of freestanding monolayers of silicene is that nobody has been able to make them yet, and it’s been questioned whether or not they can actually exist. Instead, silicene has only been observed while stuck to growth substrates, and until recently it was unclear how this would affect the properties of the material. In this seminar I will briefly outline the history of 2D materials, the development of silicene and my research into silicene grown on the Ag(111) surface.

# Seminar Thursday Aug 21 – Lindsay Goodwin

Speaker: Lindsay Goodwin
Location: Physics 175
Time: 3:30, August 21 2014

Abstract: Multi-point in situ measurements from the Swarm spacecraft in a string-of-pearls configuration provide a novel tool to investigate the creation, transport, and evolution of polar cap patches. Swarm observes a sequence of density features being created and structured in the northern Scandinavian dayside cusp by particle impact ionization. These features become entrained in the polar-cap convection pattern, and evolve into lower-density polar cap patches. Equatorward, a long-lived and robust westward flow channel is seen eroding dayside plasma. This channel prevents the dayside solar-ionized plasma from directly entering the cusp precipitation region, but possibly allows for the creation of higher-density plasma further in the polar cap. These are the first observations of a series of patches entrained in the polar cap flow, on the way from their source (the cusp) to the nightside auroral oval.

# Seminar Thursday Aug 14 – Stephanie Goertzen

Speaker: Stephanie Goertzen
Location: Physics 175
Time: 3:30, August 14 2014

Abstract: Recently, the discovery of a new class of materials called topological insulators has stimulated much excitement in the field of condensed matter physics. Their discovery has also begun the search for the exotic topological superconductor – a superconductor whose properties are protected by topology. A novel feature of such topological superconductors is the possible existence of the Majorana fermion as an elementary excitation. Traditionally, the Hamiltonian of the system is directly diagonalized in order to calculate the mean-field potentials. However this method is very computationally expensive and is widely regarded as impractical. As such, we make use of two efficient numerical algorithms that have recently been developed in order to self-consistently solve the Bogoliubov-de Gennes equations. The first is Chebyshev polynomial expansion which allows us to bypass directly diagonalizing the Hamiltonian and the second is the Sakurai-Sugiura (SS) method for efficient computation of eigenvalues and eigenvectors. Armed with this combination of techniques, we aim to investigate two-dimensional topological superconductivity.

# Seminar Thursday Aug 07 – Jason Ho

Speaker: Jason Ho
Location: Physics 175
Time: 3:30pm, August 07 2014

Title: QCD sum-rules analysis of open-charm hybrid mesons

Abstract: We briefly discuss the development of quantum chromodynamics (QCD) and introduce the concept of hadronic structures outside the quark model. Within this group of unconventional hadrons, of interest to us are hybrid mesons consisting of a quark-antiquark pair and a constituent gluon.
Through the use of QCD sum-rules, we intend to calculate the ground state mass of the $\dpi{300}\inline D$ (charm quantum number $\dpi{300}\inline c = \pm 1$) and $\dpi{300}\inline D_s$ (charm/strange quantum numbers $\dpi{300}\inline c = s = \pm 1$) hybrid mesons with exotic $\dpi{300}\inline J^{PC} = 1^{-+}$ (spin $\dpi{300}\inline J$, parity $\dpi{300}\inline P$, and charge conjugation $\dpi{300}\inline C$), and present preliminary results.

# Seminar Thursday July 17, 2014

## Seminar Thursday July 17, 2014

Speaker: Evan Smith
Location: Physics 175
Time: 3:30, July 17 2014

Abstract: Over one hundred years ago, Dutch physicist Heike Kamerlingh Onnes discovered the phenomena of superconductivity, a property wherein some materials exhibit exactly zero electrical resistance under specific conditions. The pursuit of broadening our knowledge on this peculiar phenomena has lead the scientific community to discovering new classes of materials. Some of these materials exhibit a property known as topological superconductivity. This theoretically implies the existence of Majorana fermions, which if found to exist, hold significant promise to several areas of condensed matter and material science research. Majorana fermions allow for the most theoretically stable form of quantum computation – their existence truly has the potential to usher in a new paradigm of computation and catapult society into a new era of technology.

The goal of my research is two-fold: examining the effects of various lattice inhomogeneities on crystal structure, and gaining insight into the properties of Majorana fermions and how they might exist within topological superconductors. It is necessary to understand how the creation, stabilization, and manipulation of Majorana fermions is achieved in order to evolve into this new era. At the same time, it is fundamental that we understand how a set of inhomogeneous regions influences the properties of the elusive Majorna fermion, and how we might use that knowledge to our benefit.

We make use of the Bogoliubov de-Gennes theory, a generalization of the more conventional and well-known BCS theory, and the extended Hubbard model to obtain a low-energy effective Hamiltonian which is then used to investigate the theoretical zero-energy Andreev bound states of Majorana fermions and inhomogeneities. We utilize a set of recently adapted and developed computationally efficient algorithms along with highly parallel programming to achieve our goals.

# Seminar Thursday July 3, 2014

Speaker: Amy Pitman
Location: Physics 175
Time: 3:30,  July 03 2014

Abstract: A society driven by the need for newer and faster technology, we have constantly pushed for a continued technological revolution. As advances in electronics continue to increase at a near exponential rate, we get closer to the limits of our advances in both size and speed. A recently emerged technology known as Spintronics may provide the opportunity needed to continue the trend of decreasing size by utilizing electron spin in electronic materials. While retaining the operation of traditional electronics, Spintronics allows for the opportunity to exploit a second pair of states — spin-up and spin-down — and exponentially increasing the potential logic operations. These properties are only achieved when both semiconducting and ferromagnetic properties exist simultaneously. This work focuses on one sub-set of Spintronic materials, Dilute Magnetic Semiconductors (DMSs), a class of materials which consist of a semiconductor doped with a small amount of transition-metal atoms. The primary system of interest is the semiconductor MoS2 doped with cobalt. We determine the dopant sites via the local bonding environment using cobalt L2,3 x-ray experiments and calculations while sulphur L2,3 x-ray experiments provide an estimate of the band gap.

# Viable dark matter via radiative symmetry breaking in a Higgs portal extension of the standard model

Speaker: Zhi-Wei Wang
Location: Physics 175
Time: 3:30,  June 19 2014

Abstract: We consider generation of dark matter mass via radiative
electroweak symmetry breaking in an extension of the conformal Standard Model
containing a singlet scalar field with a Higgs portal interaction. Generating the mass
from a sequential process of radiative electroweak symmetry breaking followed by
a conventional Higgs mechanism can account for less than 30% of the cosmological
dark matter abundance. However in a dynamical approach where both Higgs and
scalar singlet masses are generated via radiative electroweak symmetry breaking we
obtain much higher levels of dark matter abundance: 10%-80% for a dark matter
mass of 80 GeV < Ms < 96 GeV when higher-order contributions are estimated.
The dynamical approach also predicts a small scalar-singlet self-coupling, providing
a natural explanation for the astrophysical observations that place upper bounds
on dark matter self-interaction. The predictions in both methods are within the
detection region of the next generation XENON experiment.