Events at Physics |
Events During the Week of May 18th through May 25th, 2025
Sunday, May 18th, 2025
- Academic Calendar
- Faculty contract year ends
- Abstract: *Note: actual end time may vary.*
Monday, May 19th, 2025
- Academic Calendar
- 4-week summer session begins
- Abstract: *Note: actual end time may vary.*
- Thesis Defense
- Nanoscale imaging of viscous and nonlocal transport of electrons in graphene
- Time: 11:00 am - 1:00 pm
- Place: 5310 CH or
- Speaker: Zachary Krebs, Physics PhD Graduate Student
- Abstract: Ballistic and hydrodynamic electron flow can develop in materials when carrier momentum is conserved over long distance and time scales. These non-Ohmic transport regimes are characterized by distinctive spatial distributions of the current density and electrochemical potential. I will show scanning tunneling potentiometry (STP) measurements of the electrochemical potential induced by DC transport in graphene as a function of carrier density, temperature, and magnetic field. First, STP images are recorded as current flows through electrostatic constrictions with gate-tunable width that are "drawn" with the STM tip. The electrochemical potential drop through these constrictions determines the wavevector-dependent conductivity σ(k) of the electron fluid. Upon heating the system from 4.5 K to 77 K, enhanced electron-electron scattering leads to a crossover from ballistic to hydrodynamic flow, identified by super-ballistic conductance through the constrictions and a suppression of Landauer residual resistivity dipoles. When increasing the magnetic field from 0 to 1.4 T at 4.5 K, the STP data reveals a diffusive-to-ballistic crossover in the flow of current resulting from Landau level quantization. In the ballistic regime of magnetotransport, the local Hall field is enhanced one cyclotron diameter away from scattering surfaces.
- Host: Victor Brar
Tuesday, May 20th, 2025
- Wisconsin Quantum Institute
- Quantum Coffee Hour
- Time: 3:00 pm - 4:00 pm
- Place: Rm.5294, Chamberlin Hall
- Abstract: Please join us for the WQI Quantum Coffee today at 3PM in the Physics Faculty Lounge (Rm.5294 in Chamberlin Hall). This series, which takes place approximately every other Tuesday, aims to foster a casual and collaborative atmosphere where faculty, post-docs, students, and anyone with an interest in quantum information sciences can come together. There will be coffee and treats.
Wednesday, May 21st, 2025
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- The Hyper-Kamiokande Project
- Time: 2:30 pm - 3:30 pm
- Place: Chamberlin 5280
- Speaker: Teppei Katori, King's College London
- Abstract: Hyper-Kamiokande project consists with 3 components; Hyper-Kamiokande detector, J-PARC neutrino beam upgrade, and the near detector system. Hyper-Kamiokande detector is the 3rd generation of extremely successful water Cherenkov neutrino detectors at the Kamioka Observatory, Japan (Nobel Prize in Physics, 2002 and 2015). It is a 261 kton water tank with roughly 8 times the fiducial volume of Super-Kamiokande which will help us to push all science to an unprecedented level, including beam-based neutrino physics, astrophysics, and beyond-the-Standard-Model discovery science. In this talk, I will mainly discuss the status of the Hyper-Kamiokande detector construction and R&D.
- Host: Lu Lu
Thursday, May 22nd, 2025
- R. G. Herb Condensed Matter Seminar
- Revisiting the electron gas in the era of 2D materials
- Time: 10:00 am - 11:00 am
- Place: 5280 Chamberlin Hall
- Speaker: Miguel Morales, Center for Computational Quantum Physics, Flatiron Institute
- Abstract: Recent advances in two-dimensional (2D) and layered materials have catalyzed significant interest in the study of electrons in reduced dimensions. The discovery of exotic electronic phases in twisted bilayer graphene and transition metal dichalcogenide (TMD) bilayers has renewed focus on the properties of the 2D electron gas, which underpins most continuum Hamiltonians modeling these systems. In this talk I will present our recent efforts to explore 2D electron gases in the presence of Moire potentials, electron doping, gate screening and impurities. We employ variational and diffusion Monte Carlo methods to obtain accurate ground-state properties in parameter regimes that remain challenging for conventional numerical techniques. By leveraging novel real-space neural quantum states, the study achieves state-of-the-art accuracy in mapping the phase diagram of the homogeneous 2D electron gas. This approach yields an updated determination of the Wigner transition and reveals previously unrecognized nematic spin correlations across a broad density range in the liquid phase. Additionally, the phase diagram of the Moiré Continuum Hamiltonian, particularly for TMD heterobilayers, is investigated. The analysis characterizes the emergence of multiple magnetic orders as functions of electron density and Moiré potential depth, alongside corresponding changes in spatial correlations. Recent efforts also explore the effects of doping and impurity-induced electron localization in Moiré materials.
- Host: Matthew Otten
Friday, May 23rd, 2025
- No events scheduled