JILA Auditorium

Mid-Infrared (MIR) light can interact with molecules by selectively exciting molecular vibrational modes. In combination with photonic structures, MIR can target specific vibrational states of molecular to influence chemical reactions. In this talk, I will explain how photonic environments can modify molecular dynamics through strong light-matter coupling. This strong coupling leads to the molecular vibrational polaritons – a hybrid quasiparticle between light and matter.

The launch and commissioning of the James Webb Space Telescope is ushering in a new era in our understanding of our cosmic origins. Galaxies are a fundamental building block of the universe, yet how they formed has remained enigmatic owing to our inability to observe them at early cosmic times. In just its first three years of operation, JWST has already upended our understanding of galaxy and black hole growth in the early universe.

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.

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.

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.

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.

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.

Abstract: Achieving ballistic, coherent charge and energy flow in materials at room temperature is a long-standing goal that could unlock ultrafast, lossless energy and information technologies. The key obstacle to overcome is short-range scattering between electronic particles and lattice vibrations (phonons). I will describe two promising avenues for realizing ballistic transport in two-dimensional (2D) semiconductors by harnessing hybridization between electronic particles and long-wavelength excitations.

Due to their strong, long-range, and tunable dipolar interactions, ultracold polar molecules can realize spin-motion models with rich many-body physics. Using a spin encoded in rotational states of fermionic KRb molecules, we demonstrate tuning of Heisenberg XXZ models with electric fields and Floquet engineering of XYZ models with microwave pulse sequences. By controlling motion with optical lattices, we explore highly tunable generalized t-J models. Observing new dynamics and phases predicted for these models also requires low-entropy initial states.