Physics Department Colloquium

TBA

In 2017-2018 liquid crystal research groups working independently in the UK and Japan, exploring two distinct families of rod-shaped organic molecules, each reported an unknown nematic-like liquid crystal phases in their materials. In 2020 we showed that the unknown phase in the UK compound, RM734, was a ferroelectric nematic: a 3D liquid phase with a fluid spontaneous polarization field, P. This was a notable event in LC science because ferroelectricity was put forth in the 1910’s, by Peter Debye and Max Born, as a possible stabilizing mechanism for the nematic phase.

Moiré superlattices formed from transition metal dichalcogenide (TMDC) heterostructures have emerged as a compelling platform for exploring quantum many-body physics. These systems are viewed as a solid-state counterpart to ultracold atomic gases in optical lattices for quantum simulation. A central open question concerns the coherence and dynamics of quantum phases arising from photoexcited moiré excitons, especially under dissipative conditions.

Abstract: A new zoo consisting of dozens of heavy subatomic particles that contain more than three quarks and antiquarks have been discovered beginning in 2003.  Although they must be described by the fundamental quantum field theory QCD, the pattern of these exotic heavy hadrons remained unexplained for more than 20 years.  I will present a simple proposal for the pattern based on the Born-Oppenheimer approximation for QCD.  There are simple calculations in lattice QCD that would corroborate the pattern.

The year 2024 was a breakthrough year towards the development of a nuclear optical clock, with three experiments reporting success in the laser spectroscopy of the lowest nuclear excited state of 229-Th. The highest accuracy was achieved at JILA via direct frequency comb spectroscopy of this, previously elusive, nuclear state. This success is the result of several decades of effort to precisely determine the transition energy and a first step towards nuclear precision spectroscopy and the development of a nuclear frequency standard of extremely high accuracy.

Abstract: The most basic requirement of a scientific theory is that it make predictions. Is the Standard Model a scientific theory? As the well-tested, reigning theory of the elementary particles and fundamental forces, the Standard Model certainly claims to be able to predict the outcomes of a wide range of experiments. Yet from inelastic nuclear scattering, to neutron stars and superconductors, the universe is filled with systems whose behavior should be predicted by the Standard Model, but for which no such predictions are forthcoming!

Abstract: The 2025 Nobel Prize in Physics was awarded to John Clarke, Michel Devoret, and John Martinis “for the discovery of macroscopic quantum mechanical tunnelling and energy quantization in an electric circuit.”  This talk will give a brief history of their work and the remarkable developments that followed from it.

Abstract: Understanding thermal transport and light-matter interactions at the extreme scales is both fundamentally important and practically relevant. Studying these regimes often demand new instrumentation and high-resolution sensing techniques. In this talk, I will present my lab’s efforts to explore the complex landscape of heat transport and nanophotonics at the atomic and single-molecule scale. Specifically, we have developed microfabricated scanning thermal microscopes with picowatt- and sub-picowatt sensitivity and atomic spatial resolution.

Abstract: Magnetism is a striking example of how quantum mechanics and interactions among electrons combine to generate entirely new forms of collective behavior—phenomena that deepen our understanding of matter, as well as power modern technologies. Over the past decades, discoveries in magnetism have often heralded new paradigms in condensed matter physics, exemplified by antiferromagnetism and Mott insulators, and quantum spin liquids with their fractionalized excitations. In real materials, however, spins are inseparable from the crystalline lattices that host them.

Abstract: With the advent of the Gaia space mission, there has been a revolution in astronomers’ ability to precisely locate the interstellar structures the Sun may have encountered on its voyage around the galaxy. We now have the spatial resolution to trace the Sun’s trajectory back through its interstellar environment up to 60 million years in the past (4000 light-years in distance). This timescale is commensurate with the timescale over which we can reconstruct the paleoclimate of Earth from deep ocean foraminiferas.