Events at Physics |
Events During the Week of May 14th through May 21st, 2023
Sunday, May 14th, 2023
- Academic Calendar
- Graduate School Spring 2023: Doctoral degree deadline
- Time: 11:55 pm - 12:55 am
- Abstract: Degree candidates must complete all steps: CONTACT: 262-2433, gsacserv@grad.wisc.edu
Monday, May 15th, 2023
- Department Meeting
- Time: 12:15 pm - 1:15 pm
- Place: B343 Sterling Hall -
- Speaker: Mark Eriksson, UW-Madison
- Host: Mark Eriksson
Tuesday, May 16th, 2023
- No events scheduled
Wednesday, May 17th, 2023
- Graduate Program Event
- PhD Final Defense
- Nanoscale metrology using the spin and charge states of single nitrogen vacancy centers in diamond
- Time: 11:00 am - 1:00 pm
- Place: 5310 Chamberlin
- Speaker: Aedan Gardill, Physics Graduate Student
- Abstract: The nitrogen-vacancy (NV) center in diamond has shown great success as a nanoscale sensor due to its long coherence times at room temperature, its ability to be optically addressed, its sensitivity to a host of external fields, and having technical and logistical advantages due to being naturally trapped within the diamond. They have been used in a broad range of applications, including condensed matter physics, biology, geographical science, and commercial magnetometers. In this thesis, new nanoscale measurement techniques using single NV centers are presented that utilize their spin and charge states. First, the spin relaxation dynamics of single NV centers in nanodiamonds are measured, which sheds light on the electric noise spectral density of these nanodiamonds. Additionally, these measurements investigate the sources that limit coherence times of NV centers in nanodiamonds. Second, single NV centers are used to capture electrons released from surrounding defects in diamond in a new measurement technique. This allows us to gain new understanding of the charge dynamics of these surrounding defects. Lastly, a novel super-resolution technique is demonstrated with NV centers that uses the naturally formed Airy disk of light focused by a lens. This technique can be readily implemented in other confocal microscopes with little-to-no additional modifications.
The NV center-based measurement techniques introduced in this thesis offer promising new measurement tools that could have large impacts in other research areas, such as quantum computing. For example, the electric field sensing technique could be used to explore the source of surface charge noise in materials used in superconducting qubits or semiconductor quantum dots. The technique using single NV centers to probe charge dynamics also expands our understanding of the charge states of silicon vacancy centers in diamond, which are promising defects for quantum networks. Moreover, the demonstrated new super-resolution technique provides a gateway for other research groups to easily achieve super-resolution in their work and advance their research. - Host: Shimon Kolkowitz
- Preliminary Exam
- Investigating the Collisionless Kinetic Regime with the New TREX Drive Cylinder
- Time: 11:00 am - 1:00 pm
- Place: B343 Sterling
- Speaker: Paul Gradney
- Abstract: The Terrestrial Reconnection EXperiment (TREX) at the Wisconsin Plasma Physics Laboratory (WiPPL) can reliably reach the collisionless kinetic regime by driving an induced magnetic field through a cylindrical coil geometry. The enhanced drive reduces the effects of collisionality in the experiment, such that electron pressure anisotropy is expected to develop unimpeded by Coulomb collisions. Comparing the upgraded Drive Cylinder to the previous 4-coil TREX configuration, the reconnection current layer is a factor of two longer, with an absolute system size of L/di = 15, and increases the reconnection rate from Erec ~ 100V/m to 900V/m. These improved parameters allow the Drive Cylinder to reach a Lundquist number of S = 10^5, the highest value achieved by a dedicated reconnection experiment. In this parameter space, the Drive Cylinder can explore plasma physics dynamics that are more applicable to the collisionless settings in many space physics phenomenon, such as planetary magnetospheres.
Thursday, May 18th, 2023
- Graduate Program Event
- PhD Final Defense
- Macroscopic Dark Matter
- Time: 10:30 am - 12:30 pm
- Place: 5280 Chamberlin
- Speaker: Mrunal Prashant Korwar, Department of Physics Graduate Student
- Abstract: The notion of macroscopic dark matter, made up of multiple constituent particles, provides an intriguing possibility to explain the nature of dark matter. In this thesis, we present theoretical models, formation mechanisms in the early universe, and experimental search strategies for macroscopic dark matter. For the model aspect, we explore two examples: the electroweak symmetric dark monopole, in which the Higgs-portal interaction alters the electroweak vacuum within the monopole, and primordial black holes of both magnetically charged and uncharged types. While both uncharged black holes and magnetic black holes undergo Hawking evaporation, for the latter, the presence of hairy electroweak-symmetric coronas accelerates the Hawking evaporation, making the magnetic black holes extremal. For the formation mechanism, we propose a new production method for monopoles through parametric resonance. We demonstrate that dark monopoles with a radius up to one micron and a mass of up to ten kilotons could account for all dark matter. To search for macroscopic dark matter objects, we find that monopoles with electroweak-symmetric cores generate multi-hit signatures and deposit significant energy in large-volume neutrino detectors, such as the IceCube neutrino detector, which can probe dark matter masses up to one gram. For uncharged primordial black holes, we update constraints from Hawking evaporation using observations of gamma-ray emissions and identify new targets for future exploration. We also discuss potential detection signatures for extremal magnetic black holes.
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- WIPAC seminar
- Searches for Dark Matter with IceCube
- Time: 12:00 pm - 1:00 pm
- Place: WIPAC supernova
- Speaker: Thien Nhan Chau, Université Libre de Bruxelles
- Abstract: The nature of Dark Matter is one of the important unresolved questions in fundamental physics. It is assumed in many Beyond Standard Model theories that dark matter candidates can have weak coupling to Standard Model (SM) particles. In heavy cosmological objects, like galaxies, the Sun, or the Earth, dark matter can be gravitationally accumulated to a high abundance such that it can decay or annihilate into the anomalous flux of SM particles detectable by various detector types. This talk will provide an overview of the indirect searches for neutrino signals from Dark Matter with the IceCube Neutrino Observatory.
- Host: Lu Lu
- Preliminary Exam
- Gravitational particle production in inflationary models using Stokes phenomenon
- Time: 1:00 pm - 3:00 pm
- Place: 2223 Chamberlin
- Speaker: Nidhi Sudhir Kandathpatinharuveetil, Department of Physics Graduate Student
Friday, May 19th, 2023
- No events scheduled