Dr. Yu He, Yale University

Electronic pseudogap from fluctuations in low dimensional materials

Most metal-to-insulator and metal-to-superconductor transitions are so dramatic that certain symmetries are also concurrently broken, and an energy gap opens in lockstep with this process. But there are electronic systems that develop energy gaps without any broken symmetry, most notably the “pseudogap” in cuprate superconductors. In this talk, I will show two examples of electronic pseudogap in unexpected places: the heavily hole-doped cuprates [1], and an excitonic insulator candidate Ta2NiSe5 [2]. The former is supposedly a good metal where mean-field BCS is thought to apply, and the latter is a structural symmetry-breaking system with strong electron-phonon coupling. Via angle-resolved photoemission spectroscopy and x-ray scattering, we show the electronic gap to persist well above the transition temperature in both systems. With insights from controlled numerical calculations, we show that fluctuation is an important factor when describing the properties of low dimensional material systems. Finally, I will discuss a few new directions in the study of fluctuations.

[1] Phys Rev X 11, 031068 (2021); Nat Mater 22, 671 (2023)

[2] Phys Rev Research 5, 043089 (2023); Nat Commun 14, 7512 (2023)

Madisyn Brooks, UConn

Title and abstract TBA

Dr. Shafique Adam, Washington University in St. Louis

A narrow magic window for ultraflat bands and emergent heavy fermions near the magic angle in twisted bilayer graphene

The notion of a single “magic angle” in twisted bilayer graphene has evolved into a fascinating array of magic angles and ranges each describing different facets of the material’s behavior.  While the original continuum model predicted a nominal magic angle, its simplicity ignored the intricate interplay of different physical phenomena.  For example, lattice relaxation [1] near the magic angle shifts its value upward, only to be counteracted by pseudomagnetic fields.  Including a symmetry allowed relaxation parameter changes this magic angle to a magic range.  Yet another magic angle emerges from the coupling to phonons when the Fermi velocity equals the phonon sound velocity.  Building upon this rich tapestry of magical effects, we will discuss our recent work on the convergence of lattice relaxation and Hartree interaction near the magic angle [2]. We unveil a previously unreported Lifshitz transition to a Fermi surface topology that supports a “heavy fermion” pocket and an ultraflat band pinned to the Fermi energy. Analytical and numerical insights shed light on the narrow “magic angle range” where the “heavy fermion” is stable and make predictions for its experimental observation.  We believe that the bands presented here are accurate  at high temperature and provide a good starting point to understand the myriad of complex behavior observed in this system.

[1] “Analytical Model for Atomic Relaxation in Twisted Moiré Materials” by MMA Ezzi, GN Pallewela, C De Beule, EJ Mele, and S Adam, arXiv:2401.00498 (2024)

[2] “A self-consistent Hartree theory for lattice-relaxed magic-angle twisted bilayer graphene” by MMA Ezzi, L Peng, Z Liu, JHZ Chao, GN Pallewela, D Foo, and S Adam arXiv:2404.17638 (2024)

Prof. Luca Argenti, University of Central Florida

ASTRA: A Transition-Density-Matrix Approach to Time-Resolved Molecular Ionization

Attosecond science, which investigates the time-resolved correlated motion of electrons in atoms, molecules, and solids, is rapidly advancing toward larger molecular systems and more complex processes, such as multiple ionization and molecular fragmentation. Theoretical methods capable of addressing both multiple excitations and photofragment entanglement are essential to capture these phenomena. Among the most promising theoretical approaches are ab initio wave-function-based close-coupling (CC) methods, increasingly adopted by the AMO community.

Despite significant progress from codes like XCHEM [1,2], tRecX [3], RMT [4], and UKRmol+ [5], scaling remains a major challenge – whether in handling ionic correlation, accounting for many atoms, or for distant fragments. To address these limitations, we developed ASTRA [6] (AttoSecond TRAnsitions), an ab initio CC molecular ionization code based on high-order transition density matrices between correlated ionic states of arbitrary multiplicity [7], and hybrid Gaussian-B-spline integrals [5,9]. ASTRA integrates multiple state-of-the-art codes, such as DALTON [8], a general-purpose quantum chemistry code, LUCIA [7], a large-scale CI code, and GBTOlib [5], a hybrid integral library suited for slow photoelectrons and comparatively small molecules.

ASTRA has successfully reproduced total and partial photoionization cross sections, photoemission asymmetry parameters, and molecular-frame photoelectron angular distributions for molecules such as N ₂ , CO, H ₂ CO, and Pyrazine, showing excellent agreement with existing benchmarks. Currently, ASTRA is being applied to study attosecond transient absorption spectra of CO and O ₂ , as well as sequential XUV-pump IR-probe ionization of C ₂ H ₄ . Its formalism naturally extends to molecular double ionization and can efficiently model electron exchange between multiple disjoint molecular fragments − relevant for describing ionization in weakly bound clusters like (H ₂ O) _n .

Looking ahead, continued integration with tools tailored to high-energy photoemission, non-adiabatic nuclear dynamics, and strong fields ionization will be critical for addressing emerging challenges in ultrafast many-body dynamics. Free-electron lasers enable time-resolved studies of core ionization, while table-top attosecond pump-probe experiments are targeting increasingly larger molecules, monitoring both electron dynamics and nuclear rearrangements throughout chemical reactions with intense probe pulses [10]. To reproduce these complex experiments, we are collaborating with NIST to replace GBTOlib with a more efficient hybrid library capable of handling larger molecules and higher orbital angular momenta. We are also pairing ASTRA with surface-hopping methods [11], where multiphoton ionization is typically not available. Additionally, to track the asymptotic evolution of weakly coupled photofragments under strong light fields − without incurring prohibitive computational costs − we are considering integrating separate optimized propagators for each fragment, which will open the door for us to simulate strong-field multichannel molecular-ionization processes.

[1] M. Klinker et al., J. Phys. Chem. Lett. 9, 756 (2018).

[2] V. J. Borràs et al., Science Advances 9, eade3855 (2023).

[3] A. Scrinzi, Comput. Phys. Commun. 270, 108146 (2022).

[4] A. C. Brown et al., Comput. Phys. Commun. 250, 107062 (2020).

[5] Z. Masin et al., Comp. Phys. Commun. 249, 107092 (2020).

[6] J. M. Randazzo et al., Phys. Rev. Res. 5, 043115 (2023).

[7] J. Olsen et al., J. Chem. Phys. 89, 2185 (1988); ibid. 104, 8007 (1996).

[8] K. Aidas et al., Comp. Mol. Sci. 4, 269 (2014).

[9] H. Gharibnejad et al., Comp. Phys. Commun. 263, 107889 (2021).

[10] F. Vismarra et al., Nature Chemistry (2024).

[11] L. Fransén et al., J. Phys. Chem. A 128, 1457 (2024).

Dr. Jakob den Brok, Harvard Smithsonian Center for Astrophysics

Title and abstract TBA

Jacob Heeren, Collins Aerospace

Skill sets for data science positions in industry

Webex URL: https://uconn-cmr.webex.com/meet/drl20003

Jacob Heeren is a data analyst at Collins Aerospace, where he supports both commercial and military operations. His responsibilities span the entire data pipeline, encompassing data engineering, visualization, analytics, and governance across diverse projects. He holds degrees in psychology and applied mathematics from Iowa State University, with additional studies in astrophysics at the University of Iowa. Outside of his professional role, Jacob enjoys rock climbing and creating music, reflecting his passion for both physical and creative pursuits. Jacob will discuss his career path, current role, and useful skill sets for data science positions

Román Fernández Aranda, Department of Physics, University of Crete and FORTH Institute of Astrophysics, Greece

A Burning Hot DOG: The extreme ISM conditions of the most luminous obscured galaxy in The Universe

Hot dust-obscured galaxies (or Hot DOGs) are a remarkable population of high-redshift galaxies. Hot DOGs harbor hyper-luminous supermassive black holes (SMBHs), which are believed to provide strong feedback, creating extreme conditions in the interstellar medium (ISM) of their host galaxies in recurrent episodes of strong accretion and heavy obscuration. W2246-0526 is a Hot DOG at redshift 4.6 and the most luminous obscured galaxy known to date. I will present ALMA observations of both the brightest far-IR fine-structure emission lines and their underlying dust continuum, combined with ISM modeling of the gas and the dust. This work sheds light on the extreme conditions galaxies can experience during the early stages of the Universe, which is critical to our understanding of how distant and young galaxies evolve.

Prof. Bryce Gadway, Penn State

Synthetic Dimensions in Rydberg Atom Array

Arrays of dipolar-interacting spins - magnetic atoms, polar molecules, and Rydberg atoms - represent powerful and versatile platforms for analog quantum simulation experiments. The internal state dynamics in these dipolar arrays provide a natural setting to explore problems of equilibrium and non-equilibrium quantum magnetism. The presence of many internal states of the atoms and molecules further enables studies of large-spin magnetism, but also holds promise for more general quantum simulation studies. Here we describe how the simple addition of multi-frequency microwave fields to Rydberg arrays enables highly controllable studies of few- and many-body dynamics along an internal-state “synthetic” dimension. I’ll discuss several early studies in the Rydberg synthetic dimension platform, touching on interaction-driven phenomena relevant to topology, artificial gauge fields, and disorder-induced localization. Looking forward, such microwave manipulation opens up several new directions for exploring complex, driven quantum matter in dipolar arrays.

Dr. Tien Tien Yeh, NORDITA and UConn

Structured Light and Induced Vorticity in Superconductors

Questions of controlling the quantum states of matter via light have been at the forefront of research on driven phases. We demonstrate the effects of imprinted vorticity on superconducting coherent states using structured light. Within the framework of the generalized time-dependent Ginzburg-Landau equation, we show the induction of coherent vortex pairs moving in phase with electromagnetic wave oscillation. The structured light, generated by a Laguerre-Gaussian beam, provides light sources with various quantum properties, such as spin angular momentum and orbital angular momentum. This state of light is also well known as an optical vortex, characterized by a twisted phase front. In the current work, we investigate the optically induced dynamics of superconducting coherent states using both normal light sources and optical vortices. These results uncover rich hydrodynamics of superconducting states and suggest new optical applications for imprinting quantum states on superconducting materials.

Prof. Wenchao Ge, University of Rhode Island

How to Make a Faster Trapped-Ion Quantum Computer?

Trapped ions offer a pristine platform for quantum computation, but enhancing the interactions without compromising the qubits remains a crucial challenge. In this talk, I will present a strategy to enhance the interaction strengths in trapped-ion systems via parametric amplification of the ions’ motion, thereby suppressing the relative importance of decoherence. We illustrate the power of this approach by showing how it can improve the speed and fidelity of two-qubit gates in multi-ion systems and how it can enhance collective spin states useful for quantum metrology. Our proposal has been further demonstrated in the experiment, confirming the enhancement. Our results open a new avenue of phonon modulation in trapped ions and are directly relevant to numerous other physical platforms in which spin interactions are mediated by bosons.

Dr. Eric Koch, Harvard Smithsonian Center for Astrophysics

Revealing the multi-phase neutral interstellar medium’s role in the star formation lifecycle: a sharpened view of nearby galaxies from LGLBS and PHANGS-JWST

The neutral interstellar medium (ISM) fuels the star formation lifecycle, yet we still lack vital constraints on the formation and destruction of molecular clouds because of challenges in observing the cold neutral ISM phases with high resolution and sensitivity. With dedicated surveys, the combination of VLA, ALMA, and JWST can now make significant advances in the coming years. In this talk, I will present multiple observational approaches that are making progress in this area: detailed 21-cm HI VLA mapping across the Local Group from the Local Group L-band Survey (lglbs.org), resolved molecular cloud studies with ALMA and JWST in M33 and PAH imaging from PHANGS-JWST as a highly sensitive resolved view of the total neutral gas tracer (phangs.org). These surveys bridge Galactic with extragalactic star formation studies and provide new constraints to guide the next generation of numerical simulations.

Prof. Nikolay Prokofiev, UMass Amherst

Bi-polaron superconductivity in the low density limit

It has been assumed for decades that high values of Tc from the electron-phonon coupling are impossible. At weak-to-intermediate coupling strength this result follows from the Migdal-Eliashberg theory, while at strong coupling, when bipolarons form, the transition temperatures are low because of the exponential effective mass enhancement. However, the latter conclusion was based on numerical solutions of the Holstein model. I will discuss a different model with coupling based on the displacement modulated hopping of electrons and argue that much larger values of the bipolaron Tc can be achieved in this setup. Non-locality of the problem gives rise to small-size, yet relatively light bipolarons, which can be studied by an exact sign-problem-free quantum Monte Carlo approach even in the presence of strong Hubbard and Coulomb potentials. We find that Tc in this model generically and significantly exceeds typical upper bounds based on Migdal-Eliashberg theory or superfluidity of Holstein bipolarons, and, thus, offers a route towards the design of high-Tc superconductors via functional material engineering. Finally, there are indications for even better prospects in systems with non-linear electron-phonon coupling.

Jake Lewitt, Cortex Fusion, New York, NY

Nuclear fusion in molecules using lasers

Cortex Fusion Systems, Inc. uses shaped ultrafast laser pulses to catalyze fusion reactions in molecules. Our work comprises (1) designing transiently confining effective one-electron potentials in field-dressed molecules, (2) performing quantum chemistry calculations to validate the enhancement of nuclear tunneling by laser-modified electron screening dynamics, and (3) testing pulse shapes in the laser lab by coupling ultrafast spectroscopy techniques with nuclear radiation detection and spectrometry. In this regard, “quantum-controlled fusion” is a coherent, under-the-barrier process that does not require plasma ignition. Our goal is to repurpose the modern suite of commercial femtosecond laser amplifiers and pulse-shaping techniques to achieve compact and scalable fusion generators using quantum control.

Monica Vidaurri, Stanford University and NASA Goddard

Ethics and Aliens: the need for an ethical approach to space science

The progress of space science and exploration has seemingly inevitably fallen to private companies, to the concern of private citizens and scientists, who are directly impacted by private actions in space. Additionally, academia has reached a critical limit in terms of unchecked features that promote elitism and exclusionism, including increasingly competitive admissions to programs and fellowships, scarcity in jobs, prevalent sexual harassment, and others. As individuals, it is difficult to imagine what a truly ethical framework for our work looks like, let alone how we alone can influence laws and policy to change the actions of individuals with seemingly unlimited wealth and resources. This talk will introduce 3 main facets of what ethics means with respect to space science and exploration, including introducing space science as a historically oppressive institution, and how we can begin to move past this as individuals, labs, departments, and institutions. The norms we allow and ignore ultimately shape these broader laws, policies, and workplace culture. As a result, our science cannot be detached from the social and political framework it exists in, and the custom of early and regular collaboration with ethicists and planetary protection specialists (and other social scientists) is critical for not only mission safety, but mission and science integrity, as well as the well-being of those contributing to the mission and who gets to be included in such work. Creating a safe, responsible, and ethical space for peaceful purposes cannot wait for the international space community to create these practices de jure, but must be started at the individual level and regarded as custom for integration into international law, de facto, and require an uncomfortable self-assessment in the true goals of space science, as well as the ways that the academic structure has failed certain groups of students. By creating a new framework that prioritizes ethics, only then can we responsibly go into the unknown.

Dr. Guochao Sun, Northwestern University

Unveiling the Physics of Galaxy Formation and its Large-Scale Effects at Cosmic Dawn

Cosmic Dawn, loosely defined here to be the first billion years of cosmic time, is an ever-intriguing era that witnessed the formation of the first generations of galaxies. Toward the end of it there was also the last major phase transition of our Universe, the epoch of reionization (EoR), which is believed to be driven by the hydrogen-ionizing background emerged from the early galaxies formed. In this talk, I will explain how Cosmic Dawn becomes a real exciting epoch for unveiling the physics of galaxy formation thanks to the James Webb Space Telescope (JWST), as well as several forthcoming facilities such as SPHEREx, Roman Space Telescope, Square Kilometer Array, and LiteBIRD focusing on the large-scale effects. I will discuss the theoretical landscape galaxy formation at Cosmic Dawn informed by new JWST observations, with a particular focus on the phenomenon of bursty star formation. I will introduce methods and ideas to shed light on different aspects of early galaxy formation, including the star formation history, stellar feedback, outflows, and the ionizing output, using both individual galaxies and their effects on the large-scale structure and cosmic background radiations. With a few case studies, I will demonstrate how to harness the power of the aforementioned facilities and their synergies for these purposes.

Grad student town hall

Welcome back to UConn Astro!

Dr. Zeyang Li, Stanford University

Applying Cavity QED to Quantum Information Science

Abstract TBA

Dr. Sebastian Schenk, University of Mainz

Quantum Imprint of the Anharmonic Oscillator

We discuss the anharmonic oscillator in quantum mechanics using exact WKB methods in a ‘t Hooft-like double scaling limit where classical behavior is expected to dominate. We compute the tunneling action in this double scaling limit, and compare it to the transition amplitude from the vacuum to a highly excited state. Our results, exact in the semiclassical limit, show that the two expressions coincide, apart from an irreducible and surprising instanton contribution. The semiclassical limit of the anharmonic oscillator betrays its quantum origin as a rule showing that the quantum theory is intrinsically gapped from classical behavior. Besides an example of a resurgent connection between perturbative and nonperturbative physics, this may provide a way to study transition amplitudes from tunnelling actions, and vice versa.

Note the special room: GS 413E

Dr. Esteban Goetz, Department of Physics, University of Connecticut

Interferometric Harmonic Spectroscopy for Electron Dynamics Imaging and Attosecond Pulse Train Phase Characterization

The advent of ultrashort light pulses has opened the possibility of investigating atomic and molecular processes on their natural time scales. In particular, Attosecond Transient Absorption Spectroscopy (ATAS) [1], a technique that allows to time-resolve the quantum dynamics of electrons by monitoring the absorption of extreme ultraviolet (XUV) radiation by an atomic or molecular system when the latter is dressed by an infrared (IR) laser source.

Motivated by recent experimental advances in self-referenced interferometric harmonic spectroscopy [2], we theoretically investigate an alternative approach to ATAS for electron dynamics imaging and attosecond pulse train (APT) phase characterization. In contrast to ATAS, which gives access to the imaginary part of the refractive index through an absorption measurement, an interferometric phase measurement gives information of its real part. In this talk, I will discuss the link between the XUV phase measurements of Ref. [2] and the different photoexcitation pathways occurring at the atomic level which are imprinted in the real part of the macroscopic refractive index. As an application, we show how such an interferometric approach can be used for phase retrieval of attosecond pulse trains based on two-arm harmonic spectroscopy and an optimization algorithm. Finally, I will highlight the impact of spin-orbit couplings and macroscopic and field propagation effects on the phase measurements and APT phase retrieval. Our theoretical description is based on numerical solution of the scalar Maxwell equations beyond Beer’s Law for the macroscopic field propagation coupled to the time-dependent Schroedinger equation for the quantum dynamics.

[1] M. Holler et al., Phys. Rev. Lett. 106, 123601 (2011)

[2] G. R. Harrison et al., arXiv:2305.17263 (2023)

Prof. Claudio Chamon, Boston University

Circuit complexity and functionality: a thermodynamic perspective

We explore a link between complexity and physics for circuits of given functionality. Taking advantage of the connection between circuit counting problems and the derivation of ensembles in statistical mechanics, we tie the entropy of circuits of a given functionality and fixed number of gates to circuit complexity. We use thermodynamic relations to connect the quantity analogous to the equilibrium temperature to the exponent describing the exponential growth of the number of distinct functionalities as a function of complexity. This connection is intimately related to the finite compressibility of typical circuits. Finally, we use the thermodynamic approach to formulate a framework for the obfuscation of programs of arbitrary length – an important problem in cryptography – as thermalization through recursive mixing of neighboring sections of a circuit, which can viewed as the mixing of two containers with “gases of gates”. This recursive process equilibrates the average complexity and leads to the saturation of the circuit entropy, while preserving functionality of the overall circuit. The thermodynamic arguments hinge on ergodicity in the space of circuits which we conjecture is limited to disconnected ergodic sectors due to fragmentation. The notion of fragmentation has important implications for the problem of circuit obfuscation as it implies that there are circuits with same size and functionality that cannot be connected via local moves. Furthermore, we argue that fragmentation is unavoidable unless the complexity classes NP and coNP coincide.

Dr. Paul M. Eugenio, University of Connecticut

Tunable moire sublattices in twisted square homobilayers: exploiting fundamental principles for new technologies

Stacking and twisting atomically thin bilayers at small angles produces an approximate periodic pattern, due to the overlap of the crystal layers. These devices, dubbed “moire” bilayers, exhibit a high degree of tunability and variability: through choice of twist angle, constituent layers, and gating. To date, a number of such devices have been built which have demonstrated a plethora of novel phases, including non-trivial topology and Mott physics. Despite this explosion in moire research, moire bilayers have been almost exclusively formed from layers with triangular/hexagonal crystal geometry, and where the valence bands are centered on the Gamma or K/K’ high symmetry points. Here we theoretically demonstrate that moire devices formed from square bilayers can be used to simulate the ground state of the Hubbard model, but where the ratio of the nearest-neighbor (t) and next-to-nearest neighbor (t’) tunneling can be tuned between zero and infinity, in situ via an electric field. If experimentally realized, such a device would be the first of its kind, and would open a pathway toward the testing of a number of proposed exotic phases, such as a spin-liquid and d+id superconductivity. Most importantly, the square Hubbard model is a quintessential model for high-Tc in cuprates, where numerics has demonstrated the absence of superconductivity when t’=0.

Graduate student Geoff Harrison, Department of Physics, University of Connecticut

ITAS: A Technique for Complete Quantum Measurements on a New Timescale

Transient absorption spectroscopy is a well-established technique used to study electron dynamics in atomic and molecular systems but typically can only measure the magnitude of the electronic wavefunction. We have integrated interferometric methods into this technique to allow complete quantum measurements of both the magnitude and phase of electronic wavefunctions. A spatial light modulator (SLM) is used to separate the interferometric arms in an extremely stable way, enabling the measurement of effects on the zeptosecond timescale (with a jitter of 3zs). In this talk, I’ll describe how we’ve utilized SLMs to make these measurements possible and share some initial data we’ve taken looking at phase effects in argon.

Dr. Fatma Aslan, Jefferson National Laboratory and UConn

Hadron structure-oriented approach to TMD phenomenology

We present a first practical implementation of a recently proposed hadron structure oriented (HSO) approach to TMD phenomenology applied to Drell-Yan like processes. We compare and contrast general features of our methodology with other common practices and emphasize the improvements derived from our approach that we view as essential for applications where extracting details of nonperturbative transverse hadron structure is a major goal. These include the HSO’s preservation of a basic TMD parton-model-like framework even while accounting for full TMD factorization and evolution, explicit preservation of the integral relationship between TMD and collinear PDFs, and the ability to meaningfully compare different theoretical models of nonperturbative TMD parton distributions.

Dr. J. I. A. Li, Brown University

The Superconducting Diode Effect And Spontaneous Symmetry Breaking In Multi-Layer Graphene

The superconducting diode effect, defined as nonreciprocity in the critical supercurrent, provides a unique window into the nature of the superconducting phase. It has been argued that a zero-field diode effect in the superconducting transport requires inversion and time-reversal symmetries to be simultaneously broken. Along this vein, the zero-field superconducting diode effect in multi-layer graphene provides direct evidence of the microscopic coexistence between superconductivity and time-reversal symmetry breaking. In this talk, I will discuss our recent efforts that utilize the angle-resolved measurement of transport nonreciprocity to directly probe the nature of spontaneous symmetry breaking in the normal phase. By investigating the interplay between transport nonreciprocity, ferromagnetism, and superconductivity, our findings suggest that the exchange-driven instability in the momentum space plays a key role in the zero-field superconducting diode effect.

Graduate student Debadarshini Mishra, Department of Physics, University of Connecticut

Imaging ultrafast dynamics in molecular systems

Imaging electronic and molecular dynamics at the attosecond and femtosecond timescales is crucial for understanding the mechanisms of chemical reactions, a fundamental aspect in fields ranging from materials science to biochemistry. This in-depth understanding of chemical processes may allow for precise control over reaction dynamics, thereby paving the way for advancements in technology and medicine, for example, by guiding the development of efficient catalysis, innovative materials, and targeted drugs. In this talk, I will describe our work on imaging time-resolved molecular dynamics using two distinct and complementary techniques.

In the first part of my talk, I will discuss the use of coincident Coulomb explosion imaging for the direct visualization of roaming reactions. These reactions represent unconventional pathways that allow fragments to remain weakly bonded, leading to the formation of unexpected final products. Typically, the neutral character of the roaming fragment and its indeterminate trajectory make direct experimental identification challenging. However, I will demonstrate that by leveraging the power of coincidence imaging, we can reconstruct the momentum vector of the neutral roamer and thus identify an unambiguous signature for roaming.

In the second part of my talk, I will discuss the imaging of UV-induced ring-opening and dissociation dynamics using ultrafast electron diffraction. I will demonstrate that by harnessing the superior temporal and structural resolution of this technique, we can explore the competition among different molecular pathways as well as their wavelength-dependent behavior.

Prof. Jed Pixley, Rutgers University

Novel Strongly Correlated Phases in Stacked TMD Bilayers

Two-dimensional transition metal dichalcogenides (TMDs) have emerged as an exciting platform to stack and twist bilayers to engineer strongly correlated quantum phases. Here we present a theory to describe the recent realization of a heavy fermion state in stacked MoTe2/WSe2 bilayers. An extension of this theory that allows for the formation of unconventional superconductivity through repulsive nearest neighbor interactions will be used to show how to realize the p-wave BEC to BCS transition.

Dr. François Légaré, Institut national de la recherche scientifique, Energy Materials Télécommunications center

Ultrafast IR/mid-IR laser technologies and their applications at ALLS

The Advanced Laser Light Source (ALLS) is a unique user facility located at INRS-EMT (Varennes, Canada) counting on 40M CDN$ of investment since 2002. Since 2019, this facility has jointed the LaserNetUS network and is now funded as a national research infrastructure by the Canada Foundation for Innovation – Major Science Initiatives. These fundings ease access to the facility for academic and government users. In the first part of my talk, I will give an overview of the facility’s capabilities including the most powerful laser in Canada with 750 TW. In the second part, I will discuss novel approaches developed by my team for the generation of ultrashort pulses in the IR and mid-IR spectral range. This includes multidimensional solitary states in hollow core fibers [1,2] as well as using the frequency domain optical parametric amplification for the generation of tunable CEP stable mid-IR laser pulses [3,4]. Pulse characterization in the mid-IR spectral range will be presented [5]. Finally, I will present recent results on the generation of high-dose MeV electrons from tight focussing in air [6].

References

[1] R. Safaei, G. Fan, O. Kwon, K. Légaré, P. Lassonde, B. E. Schmidt, H. Ibrahim, and F. Légaré (2020), High-energy multidimensional solitary states in hollow core fiber, Nature Phot. 14, 733-739.

[2] L. Arias, A. Longa, G. Jargot, A. Pomerleau, P. Lassonde, G. Fan, R. Safaei, P. Corkum, F. Boschini, H. Ibrahim, and F. Légaré, Few-cycle Yb laser source at 20 kHz using multidimensional solitary states in hollow-core fibers, Opt. Lett. 47, 3612-3615 (2022).

[3] A. Leblanc, G. Dalla-Barba, P. Lassonde, A. Laramée, B. Schmidt, E. Cormier, H. Ibrahim, and F. Légaré (2020), High-field mid-infrared pulses derived from frequency domain optical parametric amplification, Opt. Lett. 45, 2267-2270.

[4] G. Dalla-Barba, G. Jargot, P. Lassonde, S. Tóth, E. Haddad, F. Boschini, J. Delagnes, A. Leblanc, H. Ibrahim, E. Cormier, and F. Légaré, Mid-infrared frequency domain optical parametric amplifier, Opt. Express 31, 14954-14964 (2023).

[5] A. Leblanc, P. Lassonde, S. Petit, J.-C. Delagnes, E. Haddad, G. Ernotte, M. R. Bionta, V. Gruson, B. E. Schmidt, H. Ibrahim, E. Cormier, and F. Légaré (2019), Phase-matching-free pulse retrieval based on transient absorption in solids, Opt. Express 27, 28998.

[6] S. Vallières, J. Powell, T. Connell, M. Evans, M. Lytova, F. Fillion-Gourdeau, S. Fourmaux, S. Payeur, P. Lassonde, S. MacLean, and F. Légaré, High Dose-Rate MeV Electron Beam from a Tightly-Focused Femtosecond IR Laser in Ambient Air (2024), Laser Photonics Rev. 18, 2300078.

François Légaré is a chemical physicist who specializes in developing novel approaches for ultrafast science and technologies, as well as biomedical imaging with nonlinear optics (Ph.D. in chemistry, 2004 – co-supervised by Profs. André D. Bandrauk and Paul B. Corkum). Full professor (2013 - …) at the Energy Materials Telecommunications center of the Institut national de la recherche scientifique (INRS-EMT), he was the director of the Advanced Laser Light Source (ALLS) until 2023. Since 2022, he is the director of the INRS-EMT center and CEO of ALLS. Under his scientific leadership, INRS has received in 2017 a grant of 13.9M CDN$ from the Canada Foundation for Innovation and the Quebec government, with 11.9M CDN$ to upscale the ALLS facility with high average power Ytterbium laser systems and advanced instrumentation for time-resolved material characterization. He is a Fellow and senior member of OPTICA and Fellow of the American Physical Society. He is a member of The College of New Scholars, Artists and Scientists of the Royal Society of Canada (2017). He was awarded the Herzberg medal from the Canadian Association of Physics in 2015 and the Rutherford Memorial Medal in physics of the Royal Society of Canada in 2016. He has contributed to about 200 articles in peer reviewed journals including prestigious ones such as Nature, Science, Nature Photonics, Nature Physics, Nature Communications, and Physical Review Letters. According to Google Scholar, his h-index is 59 with more than 13,000 citations.

Dr. Thomas Weinacht, Stony Brook University

Long Lived Electronic Coherences in Molecules

I will discuss experiments and calculations that demonstrate long lived electronic coherences in molecules using a combination of measurements with shaped octave spanning ultrafast laser pulses, 3D velocity map imaging and calculations of the light matter interaction. Our pump-probe measurements prepare and interrogate entangled nuclear-electronic wave packets whose electronic phase remains well defined despite vibrational motion along many degrees of freedom. The experiments and calculations illustrate how coherences between excited electronic states survive even when coherence with the ground state is lost, and may have important implications for light harvesting, electronic transport and attosecond science.

Dr. Yossathorn Tawabutr, University of Jyväskylä

Fully Consistent NLO Calculation of Forward Single-Inclusive Hadron Production in Proton-Nucleus Collisions

We study the single-inclusive particle production from proton-nucleus collisions in the dilute-dense framework of the color glass condensate (CGC) at next-to-leading order (NLO) accuracy. In this regime, the cross section factorizes into hard impact factors and dipole-target scattering amplitude describing the eikonal interaction of the partons in the target color field. For the first time, we combine the NLO impact factors with the dipole amplitude evolved consistently using the NLO Balitsky-Kovchegov (BK) equation with the initial conditions fitted to HERA structure function data.

The resulting neutral pion cross section with all parton channels included are qualitatively consistent with the recent LHCb measurement. In particular, the NLO evolution coupled to the leading order impact factor is shown to produce a large Cronin peak that is not visible in the data, demonstrating the importance of consistently including NLO corrections to all the ingredients. Furthermore, the transverse momentum spectrum is found to be sensitive to the resummation scheme and the running coupling prescription in the BK evolution. This demonstrates how additional constraints for the initial condition of the BK evolution can be obtained from global analyses including both the HERA and LHC data. In light of the upcoming upgrades to the LHC, the dependence of our results on rapidity will also be discussed.

Prof. Lance Dixon, Stanford University

The DNA of Particle Scattering

Scattering amplitudes are the arena where quantum field theory meets particle experiments, for example at the Large Hadron Collider where the copious scattering of quarks and gluons in quantum chromodynamics (QCD) produces Higgs bosons and many backgrounds to searches for new physics. Particle scattering in QCD and other gauge theories is far simpler than standard perturbative approaches would suggest. Modern approaches based on unitarity and bootstrapping dramatically simplify many computations previously done with Feynman diagrams. Even so, the final results are often highly intricate, multivariate mathematical functions, which are difficult to describe, let alone compute. In many cases, the functions have a “genetic code” underlying them, called the symbol, which reveals much of their structure. The symbol is a linear combination of words, sequences of letters analogous to sequences of DNA base pairs. Understanding the alphabet, and then reading the code, exposes the physics and mathematics underlying the scattering process, including new symmetries. For example, the two scattering amplitudes that are known to the highest orders in perturbation theory (8 loops) are related to each other by a mysterious antipodal duality, which involves reading the code backwards as well as forwards. A third scattering amplitude, which contains both of these as limits, has an antipodal self-duality which “explains” the other duality. However, we still don’t know `who ordered’ antipodal (self-)duality, or what it really means.