Each week during the semester, the Department of Physics invites faculty, students and the local community to hear prominent scientists discuss intriguing physics research. Unless otherwise noted, colloquia are held Tuesdays in room 1410 of the John S. Toll Physics Building at 4:00 p.m. (preceded by light refreshments at 3:30 p.m.)
For further information, please contact the Physics Department at 301-405-5946 or email This email address is being protected from spambots. You need JavaScript enabled to view it..
January 30 | Jochen Mannhart, Max Planck Institute for Solid State Research, StuttgartHosted by Rick Greene and Johnpierre Paglione
Action at the Edge: Interfaces in Superconductors and Outlaw Quantum SystemsIn this colloquium, we will embark on a fascinating journey to the frontiers of condensed-matter physics, exploring the intriguing world of superconductors and the territory of ‘outlaw’ quantum systems.Superconductors, known for their zero electrical resistance, have long been a subject of intense study. Critically, when interfaces are embedded into superconductors, they generate a rich variety of emergent properties, which lay the foundation for intriguing questions of fundamental physics as well as for applications such as the exploration of mineral resources or nuclear fusion.
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February 6 | Regina Caputo, NASA Goddard |
February 13 | Gavin Crooks, Normal ComputingHosted by Chris Jarzynski
Thermodynamic Linear AlgebraLinear algebraic primitives are at the core of many modern algorithms in engineering, science, and machine learning. Hence, accelerating these primitives with novel computing hardware would have tremendous economic impact. I'll discuss how a variety of linear algebra problems can be solved by sampling from the thermodynamic equilibrium distribution of a collection of coupled harmonic oscillators. |
February 20 | Chris Jarzynski, University of Maryland
Scaling down the laws of thermodynamicsThermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics. |
February 27 | Hitoshi Murayama, University of California, Berkeley |
March 12 | Mohammad Hafezi, University of Maryland
Topological photonicsThere are many intriguing physical phenomena that are associated with topological features --- global properties that are not discernible locally. The best-known examples are the quantum Hall effects in electronic systems, where insensitivity to local properties manifests itself as robust conductance. In this talk, we first discuss how similar physics can be explored with photons; specifically, how various topological models can be simulated in various photonics systems, from ring resonators to photonic crystals and fiber loops. We then discuss how the integration of optical nonlinearity can lead to unique bosonic phenomena, such as topological frequency combs, topological sources of quantum light and chiral quantum optics. These results may enable the development of classical and quantum optical devices with built-in protection for next-generation optoelectronic and quantum technologies. |
March 26 | Joseph Silk, Johns Hopkins University |
Thurs., March 28, 1 p.m.Irving and Renee Milchberg Endowed Lecture | Congressman Jamie Raskin Democracy, Autocracy and the Threat to Reason in the 21st CenturyPlease register: https://science.umd.edu/events/milchberg-2024.html |
April 2 | Carl Weiman, Stanford UniversityHosted by the Graduate Student Colloquium CommitteeHow to Learn to Think Like a Good Physicist and How to Teach ItFor many years, my group has been studying what makes up high level performance (“expertise”) in science and engineering (S & E), and how that expertise is best learned and taught. Being a good physicist primarily involves being able to solve novel authentic physics related problems. I will discuss how the combination of research on the development of expertise and our recent studies of the nature of S &E problem solving provides guidance for how to best learn that skill. This learning requires practicing calling on relevant knowledge to make a specific set of decisions that frame the problem-solving process of experts. I will explain how to carry out this practice in the context of physics research and courses, and discuss the research behind this approach. Although the talk will be targeted at physics graduate students, the ideas are very relevant to undergraduates and physics teachers. |
April 9 | Norm Yao, Harvard University |
April 16 | Andrea Young, UCSBHosted by Jay Sau and Sankar Das Sarma
Topology and “impossible” electronic devicesSince the discovery of quantized Hall effects in the 1980s, topology has provided a useful new paradigm for understanding condensed matter systems, expanding our vocabulary for describing the distinctions between states of matter. I will focus on how topological properties can be harnessed to build otherwise impossible electronic devices--devices whose operation, in turn, provides precise tests of the topological description of matter. In the first example, I will show how a quantized Hall effect can be realized at zero magnetic field from the spontaneous alignment of orbital magnetic moments in a graphene heterostructure. Remarkably, the large magnetic moments of the resulting chiral edge states can be used to realize an electrically actuated magnetic memory, where the macroscopic magnetic moment can be controllably reversed by charging a capacitor. In the second example, I will show how the fractionalization of charge, characteristic of topologically ordered states, can be used to create a purely direct current dissipationless step-up voltage transformer. Along the way, I will introduce the physics of van der Waals heterostructures—layered stacks of atomically thin two-dimensional crystals—and show how the remarkable experimental control available in these systems makes them the leading platform for exploring the interplay of topology and many-body quantum physics, and, potentially, realizing topologically protected quantum bits. |
April 23 | Peter Abbamonte University of Illinois, Urbana-Champaign
Observation of Pines’ demon in Sr2RuO4The characteristic excitation of a metal is its plasmon, which is a quantized sound wave in its valence electron density. In 1965, David Pines predicted that a distinct type of plasmon, which he named a "demon," could exist in multiband metals that contain more than one species of charge carrier. Consisting of electrons in two different bands beating out-of-phase, demons are acoustic excitations, meaning they are “massless,” meaning their energy tends toward zero as the momentum q ® 0. Demons may therefore play a central role in the low-energy physics of multiband metals. However, demons are neutral excitations that do not couple to light, so they have never been observed experimentally, at least in an equilibrium, 3D material. In this talk I will present the observation of a demon in the multiband metal Sr2RuO4. Formed of electrons in the β and γ bands, the demon is gapless with critical momentum qc = 0.08 reciprocal lattice units and room temperature velocity v = 1.065(120)×105 m/s. This study confirms a 67-year old prediction and suggests that demons may be a widespread feature of multiband metals. A. A. Husain, et al., Nature 621, 66 (2023)The characteristic excitation of a metal is its plasmon, which is a quantized sound wave in its valence electron density. In 1965, David Pines predicted that a distinct type of plasmon, which he named a "demon," could exist in multiband metals that contain more than one species of charge carrier. Consisting of electrons in two different bands beating out-of-phase, demons are acoustic excitations, meaning they are “massless,” meaning their energy tends toward zero as the momentum q ® 0. Demons may therefore play a central role in the low-energy physics of multiband metals. However, demons are neutral excitations that do not couple to light, so they have never been observed experimentally, at least in an equilibrium, 3D material. In this talk I will present the observation of a demon in the multiband metal Sr2RuO4. Formed of electrons in the β and γ bands, the demon is gapless with critical momentum qc = 0.08 reciprocal lattice units and room temperature velocity v = 1.065(120)×105 m/s. This study confirms a 67-year old prediction and suggests that demons may be a widespread feature of multiband metals. A. A. Husain, et al., Nature 621, 66 (2023) |
April 30 | Lee McCuller, Caltech |