Events at Physics |
Events on Thursday, September 17th, 2026
- R. G. Herb Condensed Matter Seminar
- The Atomic Single Electron Transistor
- Time: 10:00 am - 11:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Dahlia Klein, University of Chicago
- Abstract: Electrons in solids owe their properties to the periodic potential landscapes they experience. The advent of moiré lattices has revolutionized our ability to engineer such landscapes on nanometer scales, leading to numerous groundbreaking discoveries. Despite this progress, direct imaging of these electrostatic potential landscapes remains elusive. Here, we introduce the Atomic Single Electron Transistor (SET), a novel scanning probe that uses a single atomic defect in a van der Waals (vdW) material as an ultrasensitive, high-resolution potential sensor. Built upon the quantum twisting microscope (QTM) platform, this probe leverages the QTM’s capability to form a pristine, scannable 2D interface between vdW heterostructures. Using the Atomic SET, we present the first direct images of the electrostatic potential in a canonical moiré interface: graphene aligned to hexagonal boron nitride. This potential exhibits an approximate C_6 symmetry, minimal dependence on carrier density, and a substantial magnitude of ~60 mV even in the absence of carriers. Theory indicates that this symmetry arises from a delicate interplay of physical mechanisms with competing symmetries. Intriguingly, the measured magnitude significantly exceeds theoretical predictions, suggesting that current understanding may be incomplete. With 1 nm spatial resolution and sensitivity to potentials generated by only a few millionths of an electron’s charge, the Atomic SET enables ultrasensitive imaging of charge order and thermodynamic properties across a wide range of quantum phenomena, including symmetry-broken phases, quantum crystals, vortex charges, and fractionalized quasiparticles.
- Host: Tiancheng Song
- Astronomy Colloquium
- Tracking the Grist and Flakes of Planetesimals with Dust Polarization
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Daniel Lin, Jansky Postdoctoral Fellow, NRAO
- Abstract: How planetesimals form and evolve in circumstellar disks is one of the most important questions in astrophysics. In this talk, I will demonstrate that polarization is a unique tool for studying the properties of dust grains throughout the planet formation process. In protoplanetary disks, ALMA has revolutionized the field of disk-scale polarization by detecting and resolving percent-level polarization. I will first present observational evidence of large, scattering, aligned grains. I will then introduce a new grain alignment mechanism that can trace the relative motion between dust and gas offering a connection to how planetesimals form. In debris disks, where planetesimals have fully formed, I will demonstrate how dust polarization, aided by neural networks, can constrain dust composition.
- Host: Nicholas Stone