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Colloquium

The colloquium is currently held at 4:15 PM on Tuesdays in Harriman 137. Cookies, tea and coffee are served from 4:00 PM outside the lecture hall.

Colloquium committee: Rouven Essig (Chair), Jennifer Cano (Vice Chair), Abhay Deshpande, Will Farr, Harold Metcalf, Jesus Perez Rios, Giacinto Piacquadio

Archive of colloquia from 1999 to the present


Fall 2023 Colloquia
Date Speaker Title & Abstract

Sep 5

Chang Kee Jung

Stony Brook University

Chair's Colloquium

Sep 12

Chris Greene

Purdue University

Universal Physics of 2 or 3 or 4 Strongly Interacting Particles


Recent developments in the field of a few interacting particles with nonperturbative interactions will be reviewed, focusing on ultracold atomic and molecular physics, but with one recent application to the few-nucleon problem as well. Some of these studies are intimately connected with the Efimov effect, while others go beyond the standard Efimov effect with its remarkable infinity of long-range energy levels. Some of our relevant references addressing those topics are listed below.

[1] Nonadiabatic Molecular Association in Thermal Gases Driven by Radio-Frequency Pulses, Phys. Rev. Lett. 123, 043204 (2019), with Panos Giannakeas, Lev Khaykovich, and Jan-Michael Rost.
[2] Nonresonant Density of States Enhancement at Low Energies for Three or Four Neutrons, Phys. Rev. Lett. 125, 052501 (2020), with Michael Higgins, Alejandro Kievsky, and Michele Viviani
[3] Efimov physics implications at p-wave fermionic unitarity, Phys Rev A 105, 013308 (2022), with Yu-Hsin Chen.
[4] Ultracold Heteronuclear Three-Body Systems: How Diabaticity Limits the Universality of Recombination into Shallow Dimers, Phys. Rev. Lett. 120, 023401 (2018), with Panos Giannakeas.

Sep 19

Serge Haroche

Nobel Prize Recipient, 2012

C.N. Yang Colloquium


Click the image below to see the event poster!
cn yang 2 poster

Sep 26

Jan Bernauer

Stony Brook University

Exploring the Standard Model with lepton scattering at the precision frontier


In the last 100 years, accelerator-based nuclear physics has made incredible advances on the precision frontier: the capability to achieve ever shrinking measurement uncertainties, driven by higher luminosities, better detectors, new experimental techniques, and improved theoretical corrections. This is especially true for lepton scattering, predominantly using electron beams, with a renaissance in positron and muon beams.

In this talk, I will cover three topics. First, I will show how such precision measurement can help us understand non-perturbative quantum chromodynamics, focusing on the so-called “proton radius puzzle”, the proton form factors, and the MUSE experiment. Second, I will discuss how one can search for Beyond the Standard Model physics with precision lepton scattering, in the context of the DarkLight@ARIEL measurement and the ATOMKI anomalies. Third, I will explain how Streaming Readout will advance our capabilities for precision measurements.

Oct 3

Antoine Georges

Collège de France, Paris

Flatiron Institute, New York

The Diverse Routes to Strong Electronic Correlations: A Dynamical Mean Field Theory Perspective


From transition-metal oxides, rare-earth and organic compounds to moiré two-dimensional materials, strong electronic correlations have focused enormous attention over several decades. In this talk, I will emphasize three main mechanisms responsible for strong electronic correlations. The proximity to a Mott insulator, and the Kondo effect leading to heavy fermion behavior have been known for a while. Recently however, it became apparent that the properties of a broad family of materials (including iron-based superconductors) cannot be explained within the Mott or the heavy fermion paradigms. The intra-atomic exchange turns out to be the main player responsible for the properties of these "Hund metals."

The classic band theory of solid-state physics must be seriously revised for strongly correlated materials. Instead, a description accounting for both localized atomic excitations and delocalized wave-like quasiparticles is required. I will review how Dynamical Mean-Field Theory (DMFT) fulfills this goal and provides an original physical perspective on strongly correlated electron materials. Thanks to the efforts of a whole community over almost three decades, the theory now provides a practical framework to understand and predict the properties of quantum materials starting from their structure and chemical composition.

Oct 10

No Colloquium.

Fall Break.

Oct 17

Gregory Falkovich

Weizmann Institute of Science

Zero charge and confinement in turbulence


I will describe an attempt to do renormalization in turbulence, considering waves that interact weakly via four-wave scattering (such as sea waves, plasma waves, spin waves, and many others). By summing the series of the most UV-divergent terms in the perturbation theory, we show that the true dimensionless coupling is different from the naive estimate, and find that the effective interaction either decays or grows explosively along the cascade, depending on the sign of the new coupling. The explosive growth possibly signals the appearance of a multi-wave bound state (solitons, shocks, cusps) similar to confinement in quantum chromodynamics.

Oct 24

Aida El-Khadra

University of Illinois Urbana-Champaign

The dance of the muon


More than eighty years after the muon was first identified it may serve as a window to discovering new physics. Thanks to new experimental measurements at Fermilab, the muon’s magnetic moment is now known with an exquisite precision of 189 parts per billion, sharpening the longstanding tension between experiment and theoretical expectations. The experimental measurements will continue to improve with the ultimate goal of reducing the experimental uncertainties to 120 parts per billion. The theoretical calculations of the muon’s magnetic moment must account for the virtual effects of all particles and forces within the Standard Model, where effects coming from virtual hadrons, governed by the strong interactions, are by far the largest sources of theory uncertainty. Recent estimates of hadronic corrections have created puzzles on the theory side, which are currently being investigated. I will discuss the ongoing interplay between theory and experiment that is essential to unlocking the discovery potential of this effort.

Oct 31

Laszlo Forro

University of Notre Dame

Status quo in superconductivity


Since the groundbreaking discovery in 1911 of a zero-resistance state at 4 K – an outcome then dubbed the "impossible result" – the realm of superconductivity has captivated researchers worldwide. One of the primary aspirations since has been to elevate critical temperatures to ambient conditions, a milestone that would revolutionize energy transport, diagnostics, and information technologies, among other sectors. Recent studies have reported achieving this objective under both extreme pressures and even at standard atmospheric conditions. This colloquium provides a comprehensive overview of the present advancements in superconductivity, including findings from our dedicated research endeavors.

See speaker bio here.

Nov 7

Cyrus Dreyer

Stony Brook University

Perfecting quantum imperfections


One of the key impacts of condensed-matter physics is its role in predicting, developing, and understanding materials for technological applications, e.g., transistors, light-emitting diodes, and solar cells. In this context, it is not enough to just understand the pristine materials that make up the devices; the imperfections in those materials must also be characterized and understood. In particular, point defects, which are atomic scale imperfections or impurities in the crystal lattice, are ubiquitous in all materials and can have profound effects on their properties and phenomena. Recently, it has been demonstrated that individual point defects are robust and manipulatable quantum systems that can be used as qubits for quantum computing, emitters of single photons for quantum communication, and nanoprobes for quantum metrology. Ab-initio theoretical methods are crucial for understanding defects in both conventional and quantum devices, since their dilute concentration and small size make them difficult to directly characterize experimentally. At the same time, accurate quantitative knowledge of defect properties is necessary to mitigate detrimental defects and utilize beneficial ones. Defects are also challenging for theory as their properties may depend on highly correlated electronic excited states that have complicated coupling to the host crystal lattice. In this colloquium, I will describe new methods we have developed to study quantum defects from first principles, which allow simple but quantitatively accurate models of defect properties to be parametrized and solved. I will give example of how we are using these methods to search and characterize for quantum defects for the next generation of quantum devices.

Nov 14

Wolf Schäfer

Stony Brook University

Robot Ethics and the Plurality of Theories Problem


This talk is about a difficulty that emerges when humans build powerful things involving science, technology, and society. My case in point are self-driving cars, i.e., automated vehicles (AVs).

Since physicists succeeded in building nuclear bombs, “science has become much too important to be left to the scientists” (Conant). Contemporary examples of this challenge include genome editing with CRISPR in biotechnology and generative artificial intelligence (AI) with large language models in computer science.

The expectation of a dramatic reduction in road traffic accidents after the transition to AVs is well-founded. However, the idea that all traffic accidents will be a phenomenon of the past is utopian. My students and I assume that these accidents will decline, but still happen, and that societal scrutiny of robot car fatalities will increase, especially in some edge cases, where the automotive AI will compute alternative outcomes and make an unforced decision based on different (non-universal) ethical theories, such as utilitarianism or Kantianism.

Nov 21

No Colloquium

Thanksgiving Week.

Nov 28

No Colloquium

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Dec 5

Keshav Dani

Okinawa Inst. of Sci. & Tech. Graduate University

Imaging photoinduced phenomenon in real and momentum space


Photoemission spectroscopy techniques – wherein one photoemits an electron from a material using a high-energy photon to study its properties – have provided unparalleled insight into materials and condensed matter systems over the past several decades. Among these, there are two particularly powerful and complementary techniques: angle-resolved photoemission spectroscopy (ARPES), which resolves the momentum of the photoemitted electron in the material; and photoemission electron microscopy (PEEM), which resolves its spatial coordinate. Recently, the merger of these techniques into multi-dimensional platforms of photoemission spectroscopy, along with access to the temporal dimension by further incorporating ultrafast spectroscopy techniques, have enabled powerful visuals of the dynamics of photoexcited systems in real and momentum space.

In the first part of the talk, I will discuss some recent work in my lab in visualizing photoexcited carriers in space, time and energy [1, 2]. Applying these techniques to state-of-the-art perovskite photovoltaic films, we will image the performance limiting nanoscale defect clusters in these next-gen solar materials [3], and understand their role in charge trapping [4, 5].

In the second part of the talk, we will turn our attention to imaging momentum space in photoexcited 2D semiconductors and heterostructures [6]. Thereby, we will directly image the distribution of an electron around a hole in an exciton [7] – a hydrogen-like state that forms when a semiconductor absorbs light; visualize dark excitonic states that have largely remained hidden to optical experiments [8], and observe the structure of a moiré trapped interlayer exciton [9].

[1] Nature Nanotech.12, 36 (2017)
[2] Science Advances4, eaat9722 (2018)
[3] Nature580, 360 (2020)
[4] Energy & Environ. Science14, 6320 (2021)
[5] Nature 607, 294 (2022)
[6] Advanced Materials DOI 10.1002/adma.202204120 (2022)
[7] Science Advances7, eabg0192 (2021)
[8] Science370, 1199 (2020)
[9] Nature603, 247 (2022) 


Tentative Spring 2024 Schedule

Date Speaker Title & Abstract

Feb 6

Chiara Mingarelli

Yale

TBA.


Archived Colloquium Schedules