Events at Physics |
Events on Thursday, November 20th, 2025
- R. G. Herb Condensed Matter Seminar
- Disorder-induced fractionalization of pair density waves
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Julian May-Mann, Stanford University
- Abstract: Pair-density waves (PDWs) are unconventional superconductors in which the order parameter periodically oscillates in space. Compared to other superconductors, PDWs are particularly susceptible to disorder, since random impurities can disrupt the periodic structure that defines them. However, it is not clear whether disorder completely destroys the PDW or instead gives rise to a new phase. Here, we show that a new phase can indeed arise, by considering a strongly inhomogeneous limit in which the system consists of a random collection of PDW puddles embedded in a metallic background*. When the puddles are dilute, they become phase coherent at low temperatures, resulting in a state that is macroscopically equivalent to an s-wave superconductor. This can be viewed as an example of order-parameter fractionalization, in which the PDW order splits into an s-wave superconducting component and a charge-density-wave component, the latter of which is destroyed by disorder. This result highlights the unexpected robustness of superconductivity in PDWs and provides new insights into the effects of disorder on d-wave superconductors.
- Astronomy Colloquium
- Planet-Forming and Photoevaporating Disks in the Orion Nebula Cluster: The View from ALMA and JWST
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Dr. Nick Ballering, Research Scientist at SSI/UW-Madison
- Abstract: The Orion Nebula Cluster (ONC) offers the clearest view of protoplanetary disks in a rich cluster, the typical environment for star and planet-formation in the Galaxy. I will present results from high-resolution ALMA observations of over 200 disks in the ONC that reveal their dust masses and sizes, key properties in determining what types of planets can form. I will also highlight images of proplyds—disks in the process of being photoevaporated by the cluster’s harsh radiation field—where ALMA traces free-free emission and radio recombination lines from outflowing ionized gas. I will then turn to the infrared and share recent JWST NIRSpec observations of warm atomic and molecular gas from three ONC proplyds. Finally, I will show how JWST NIRCam observations can reveal the presence of water ice in an edge-on disk seen in silhouette in front of the Orion Nebula.
- Host: Nicholas Stone