Abstract: While the properties of soft materials are ultimately dictated by their electronic structure, exploiting this knowledge for the design of non-crystalline materials has long been a formidable computational challenge. I will define conceptual and practical barriers that limit quantum mechanical design in soft materials and discuss recent work aimed at removing these barriers. First, I will describe the development of electronic structure models that leverage AI to operate at coarse-grained resolutions, enabling electronic design in non-crystalline molecular solids and polymers. Second, I will discuss how AI-driven strategies, tightly coupled with experimentation, can tackle soft materials reactivity challenges outside of the purview of traditional theoretical and computational methods. These developments chart a path towards predictive soft materials engineering grounded in electronic structure and chemical reactivity.

How big would Mercury need to be to retain an atmosphere? How close could Venus orbit the Sun before its atmosphere erodes away? Are habitable Earth-like atmospheres even possible around the smallest stars? In this talk, I describe how exoplanet observations are starting to provide insight on what environments permit terrestrial planet atmospheres to thrive. I present a new probabilistic model for a boundary between planets with and without atmospheres, one that is rooted in remotely measurable quantities, accounts for how drivers of atmospheric loss can change strongly with stellar type, and quantifies the charming, complicated, crinkly, chaotic fuzziness of planets’ diverse individual life histories. I use this model to predict where we might most productively search for rocky exoplanet atmospheres in the near future, I highlight work we are doing to mitigate the astrophysical challenges currently limiting us from observing some of those planets, and I outline goals for continuing to train generations of Colorado Researchers in Observing Chromatic Exoplanet Time-series (CROChET) with curiosity, creativity, coding, and kindness.

Quantum metrology enables some of the world's most sensitive measurements with potentially far-reaching applications in the life sciences. Although the ultrahigh sensitivity of qubit sensors has sparked the imagination of researchers, implementing them in actual devices that enable monitoring cellular processes or detecting diseases remains largely elusive. Overcoming the limitations that hinder the broader application of quantum technology in the life sciences requires advances in both fundamental science and engineering. In this talk, I will discuss new strategies that combine quantum engineering and molecular biology to develop a new generation of quantum sensors that can be readily integrated with biological systems. My discussion will start with the development of a novel biocompatible surface functionalization architecture for highly coherent diamond crystals. I will then continue with discussing a new approach to engineering spin coherence in core-shell structured diamond particles, which can be readily chemically modified and delivered to intact biological systems. Finally, I will depart from established diamond sensors and introduce an entirely new class of biological qubits based on optically-addressable spins in fluorescent proteins. These protein-qubits have coherence times and optical readout comparable to solid-state defects, but are only 3 nm in diameter and genetically encodable. The unifying theme of these advances is the convergence of techniques from quantum engineering and molecular biology. Specific applications of the developed sensing platforms to questions in the life sciences will be discussed throughout this talk. 

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Host: Ana Maria Rey

Abstract: Proteins operate within an aqueous environment that influences their folding, stability, and activity. Membrane proteins have the added complication of being embedded in lipid bilayers that play an equally critical, yet significantly less understood, role. Much like solvent conditions modulate enzyme kinetics and protein interactions in solution, the lipid composition of the membrane performs regulatory functions for membrane proteins, affecting their organization, conformational dynamics, and catalytic output. To investigate these membrane-dependent phenomena, we employ time-resolved fluorescence spectroscopy techniques like pulsed interleaved excitation fluorescence cross-correlation spectroscopy (PIE-FCCS) in model membranes and live cells. We couple these spectroscopic probes with liposome-based activity assays in vitro. These complementary approaches allow us to quantitatively assess how specific lipid species influence the assembly and function of receptor tyrosine kinases (RTKs).

In this talk, I will highlight two key areas where lipid–protein interactions govern RTK behavior. First, I will describe how the anionic lipid phosphatidylinositol 4,5-bisphosphate (PIP₂) promotes multimeric assembly of EGFR and EphA2 in the plasma membrane, driving the formation of functionally distinct signaling complexes, as revealed by PIE-FCCS in live cells. Second, I will present our recent in vitro findings showing that both PIP₂ and phosphatidylserine (PS) act as reversible, noncompetitive inhibitors of EGFR catalytic activity in a reconstituted liposome system, demonstrating direct biochemical regulation of kinase function by anionic lipids. Together, these results reveal that the lipid bilayer is not merely a scaffold but an active participant in membrane protein regulation. By drawing parallels to the well-established influence of solvent on soluble proteins, we hope to center the membrane environment as a dynamic and tunable component of cell signaling.

The availability of exascale computing resources has enabled numerical modeling of astrophysical fluid dynamics at unprecedented scale, including studies of MHD turbulence on grids with 10,000^{3} cells, or MHD models of black hole accretion in full GR with radiation transport. Results from a diverse range of applications will be presented, including new insights into the structure of radiation-dominated accretion disks, modeling AGN feedback in elliptical galaxies, and turbulence and cosmic ray transport in the interstellar medium.

Abstract: Social bonds live in our biology. To understand the computations that allow our brains to form social bonds, my lab studies monogamous prairie voles. Unlike laboratory mice and rats, these rodents often mate for life, parenting together and defending a shared home. We have found that social information is organized at multiple scales in the brain's reward center—from stable encoding in individual neurons to coordinated ensembles—to enable bond formation. Once these bonds are formed, they lead to an alignment of brainscapes between partners, evident in patterns of neural activity and molecular alignment. Ultimately, this work delineates how social relationships change the brain beginning with their initial encoding mechanisms and then establishing a framework that facilitates connectedness and may help pairs effectively navigate the world together.

Abstract: My talk will highlight new directions in probing semiconductor electrochemistry and reactivity at the single-particle and single-molecule level. I will discuss our recent discovery that the band gap renormalization (BGR) effect in 2D semiconductors strongly dictates their current–voltage behaviorin electrochemical cells, providing a new framework to understand solid-state transistor device performance variability. I will then describe how single-particle photoelectrochemistry of BiVO₄ reveals unexpected facet-dependent heterogeneity that links structural defects and surface terminations to reactivity. Finally, I will present super-resolution imaging results of surface defect states in semiconductor nanocrystals, where direct visualization opens new possibilities for correlating local electronic structure with photophysical function. Together, these studies illustrate how multi-scale imaging and spectroscopy can unravel fundamental mechanisms of charge generation, separation, and storage in semiconductor materials for energy conversion.

Parker Solar Probe successfully completed its prime mission in 2025, measuring solar wind plasma in-situ as close as 8.8 solar radii (~0.04 AU) from the solar photosphere over a series of close-approach orbits. These close approaches to the Sun enable novel exploration of fundamental stellar processes, such as solar wind acceleration, solar wind heating, interplanetary dust destruction, and radial evolution of solar surface structure. These processes leave distinct signatures in near-Sun particle and field observations that allow us to untangle the physical mechanisms driving them. Further, travel through the extreme near-Sun environment has revealed a new regime of strong interactions between a spacecraft and its plasma environment. Insights gained from exploring the physics of these interactions have directly led to novel measurement capabilities on sounding rockets, small sats, lunar landers, and flagship space science missions. This talk focuses on advances in solar wind physics made over the course of the Parker Solar Probe mission, as well as on new space plasma measurement capabilities inspired by these studies.

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Abstract: Polaritons are hybrid light-matter states with unusual properties that arise from strong interactions between a molecular ensemble and the confined electromagnetic field of an optical cavity. Cavity-coupled molecules appear to demonstrate energetics, reactivity, and photophysics distinct from their free-space counterparts, but the mechanisms and scope of these phenomena remain open questions. I will discuss new experimental platforms that the Weichman Lab is developing to investigate molecular reaction dynamics under strong cavity coupling.

While polaritons are now well-established in solution-phase and solid-state systems, they had not been previously reported in isolated gas-phase molecules, where attaining sufficiently strong light-matter interactions is a challenge. We access the strong coupling regime in an intracavity cryogenic buffer gas cell optimized for the preparation of simultaneously cold and dense ensembles and report a proof-of-principle demonstration in gas-phase methane. We strongly cavity-couple individual rovibrational transitions and probe a range of coupling strengths and detunings. In ongoing work, we are harnessing this infrastructure as a testbed for fundamental studies of polariton physics and chemistry.

We are also searching for signatures of cavity-altered dynamics in benchmark solution-phase systems. So far, we have focused on radical hydrogen-abstraction processes, which have well-characterized reactive surfaces and can be initiated with photolysis and tracked directly on ultrafast timescales. We use ultrafast transient absorption to examine intracavity reaction rates with the goal of better understanding exactly how and when reactive trajectories may be influenced by strong light-matter interactions.

The Department of Physics at the University of Colorado Boulder in collaboration with CUbit and JILA is hosting the third annual Physics and Quantum Career & Internship Fair on Friday, October 17^th from 12:00 - 3:00 p.m. in the Glenn Miller Ballroom.

This event will feature employers across all areas of theoretical, experimental, and computational physics. The fair will connect physics undergraduate and graduate students and recent alumni with laboratory and industry leaders to learn about internships and employment opportunities.

Sign up online

Handshake is CU's online recruiting tool used by thousands of employers. It is recommended, but not required for students to sign up for the 2025 Physics and Quantum Career Fair on Handshake.

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Control of spin and valley polarizations opens opportunities for spintronic and quantum information applications. Monolayer transition-metal dichalcogenides (TMDs) offer an appealing platform to harness such polarizations. TMDs host excitons in valley-shaped regions of their band structure, featuring well-defined carrier spins and obeying chiral optical selection rules. However, the technological potential of excitons in TMDs is impeded by rapid spin–valley relaxation.

I will present our theoretical/computational efforts to address and enhance spin–valley polarizations in TMDs through strong coupling to photons. Recognizing that chiral light is a manifestation of photonic spin, I will show such strong coupling to allow for efficient spin transduction through the formation of "chiral polaritons". I will furthermore show how a breaking of chiral symmetry in optical cavities allows valley–spin relaxation to be suppressed in embedded TMDs.

I will also discuss our efforts to unravel how spin–valley relaxation in TMDs is driven by lattice phonons. Towards this goal, my group has advanced nonadiabatic methodologies that allow delocalized phonon modes and topological effects to be incorporated within a mixed quantum–classical framework. Results for TMDs indicate this approach to enable the modeling of solid-state phonon-driven processes at realistic dimensionalities.

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