Events at Physics |
Events on Thursday, November 14th, 2024
- R. G. Herb Condensed Matter Seminar
- Extrinsic and intrinsic superconducting diode effects
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Jukka Vayrynen, Purdue University
- Abstract: The critical current of a superconducting wire can be non-reciprocal, i.e., dependent on current direction, when inversion and time-reversal symmetry are broken. This so-called superconducting diode effect has gained renewed attention in recent years, due to the possibility that the effect may arise from the interplay of spin-orbit coupling and Zeeman effect in a uniform superconductor. I will discuss the superconducting diode effect originating from two different mechanisms, studied in recent preprints [1-2]. The first one is an extrinsic one arising from the geometry of the setup rather than intrinsic properties. It is however relevant for uniform superconducting heterostructures due to the formation of interfacial diamagnetic currents and Josephson vortices [1]. In the second part of the talk, I will discuss an intrinsic mechanism that is relevant for generic quasi-one-dimensional superconducting system where the critical current is determined by Cooper pair depairing. By introducing a minimal model, we find the key ingredients to obtain intrinsic superconducting diode effect. The model can be microscopically derived as a low-energy limit of a Rashba spin-orbit coupled superconductor in a Zeeman field [2] or of an edge state of a two-dimensional topological insulator [3]. The results quantify how system parameters such as spin-orbit coupling and quantum confinement affect the strength of the diode effect and provide a complementary description to previous Ginzburg-Landau theories of the effect. [1] Diamagnetic mechanism of critical current non-reciprocity in multilayered superconductors, Sundaresh, Vayrynen, Lyanda-Geller, Rokhinson, arXiv:2207.03633. [2] Superconducting diode effect in quasi-one-dimensional systems, de Picoli, Blood, Lyanda-Geller, Vayrynen, arXiv:2302.04277 [3] Superconducting Diode Effect in Two-dimensional Topological Insulator Edges and Josephson Junctions, Huang, de Picoli, Vayrynen, arXiv:2404.14566
- Host: Elio König
- Wisconsin Quantum Institute Colloquium
- Engineering a topological quantum computer
- Time: 3:30 pm - 5:00 pm
- Place: Discovery Building, DeLuca Forum
- Speaker: Brad Lackey, Microsoft
- Abstract:
I will provide a high-level introduction to Majorana qubits and show some recent experimental results at Microsoft that realize these in nanowire devices. I will then present a potential computing stack for a topological quantum computer based on Majorana qubits and provide some estimates about the capabilities of such a machine on some applications of scientific and industrial value.
This event starts at 3:30pm with refreshments, followed at 3:45pm by a short presentation titled "Efficient implementation of qLDPC codes with neutral atom qubits", by Cody Poole (Saffman group). The invited presentation starts at 4pm.
- Host: Mark Saffman
- Astronomy Colloquium
- An Equity-Minded Approach to Graduate Education: The Wisconsin Sloan Center for Systemic Change
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Erika Marín-Spiotta, UW-Madison
- Abstract: The Wisconsin Sloan Center for Systemic Change, or WiSC2, is a hub for innovating and leading transformative work for excellence in graduate education at UW. Supported by the Alfred P. Sloan Foundation, the aim of Systemic Change centers is to remove entrenched barriers to student success, improve student outcomes, and create educational environments that are more equitable and effective for all. Research at UW–Madison and elsewhere has shown that student success is influenced by students’ academic preparation and self-efficacy and their sense of community and their feelings of belonging. This is especially true for students from backgrounds historically excluded from higher education and from science.
- Host: Melinda Soares-Furtado