Dr. Sang Mo Yang, Sogang University, South Korea

Title: Ferroelectricity at the Nanoscale: Emerging Materials and Local Probes

Abstract: Ferroelectricity on the nanoscale has been the subject of considerable interest in condensed matter physics for over half a century. Beyond its fundamental importance, ferroelectricity provides essential functionality for advanced electronic devices, including nonvolatile memories, field-effect transistors and tunnel junctions. 

However, conventional perovskite-based ferroelectric oxides (e.g., Pb(Zr,Ti)O3) face significant challenges in achieving device performance that can compete with current dynamic random-access memories and flash memories. Over the past decade, novel ferroelectricity has been discovered in new material systems, including fluorite-structured HfO2-based thin films, two-dimensional (2D) van der Waals (vdW) materials and 2D perovskite halides. These discoveries have brought about a renaissance in the ferroelectric research community. 

In this colloquium, I will present our group’s recent efforts to investigate and understand ferroelectricity across these emerging material platforms [1] using various scanning probe microscopy techniques.
[1] T. H. Jung et al., “Spatially Resolved Observation of Ferroelectric-to-Paraelectric Phase Transition in a Two-Dimensional Halide Perovskite,” Advanced Materials 37, 2506270 (2025)

Dr. Joel Leja, Penn State University

Title: Alien oceans: hot springs, phosphorus, and the search for life in the solar system

Abstract: The discovery of liquid water oceans on Saturn’s moon Enceladus in 2006 and as many as a dozen other moons in the solar system (most notably Jupiter’s moon Europa) has greatly changed our understanding of our solar system’s "habitable zone." Rather than simply searching for liquid water, planetary scientists now need a framework to assess the relative likelihood of different planetary targets to host the physical and chemical ingredients required to support detectable biology. 

In this talk, I will discuss the planetary (hydrothermal) and exogenous (meteoritic sedimentation) processes leading to nutrients and bioavailable energy on ocean moons. I show how even a relatively tectonically quiescent seafloor can lead to hydrothermal circulation. I will then focus on a specific bioessential nutrient produced by this circulation: phosphorus that was recently discovered on Enceladus. Our published results anticipated those observations to within analytical error of the satellite. I show how models integrating stellar stoichiometry and an understanding of thermodynamics and fluid dynamics can lead to testable predictions of icy moon ocean chemistry. Finally, I discuss the implications for exoplanet and future planetary science missions. 

Dr. Akash Gupta, Princeton University

Title: Connecting the Dots: From Electrons to Planets

Abstract: The most common planets observed to date fall between the sizes of Earth and Neptune. I will present how my work, together with recent studies, demonstrates that most of these planets accreted hydrogen-helium envelopes from their protoplanetary disks. Over millions to billions of years, some lose these primordial atmospheres through escape processes and emerge as rocky super-Earths, while those that retain their envelopes correspond to the population observed today as sub-Neptunes.

This evolutionary pathway has profound implications for interpreting the diversity of atmospheres now being revealed by the James Webb Space Telescope and for designing future surveys. In particular, these hydrogen-helium-dominated atmospheres are expected to interact strongly with their molten or supercritical interiors over much of their lifetime. Yet, despite their central role in planetary evolution, our fundamental understanding of these atmosphere-interior interactions remains limited, largely because they occur under extreme pressures and temperatures that are difficult to access experimentally.

I will present new quantum-mechanical insights into how key planetary materials — hydrogen, helium, water, silicates and iron — interact and transform under conditions relevant to Earth-to- Neptune-mass planets. I will discuss how these results challenge long-held views on the evolution and structure of planets and outline their implications for interpreting current and future observations, including those from JWST, as well as upcoming missions and facilities such as the Uranian Orbiter and Probe, the Habitable Worlds Observatory and ELTs.

Title: Exact Transition Amplitudes in Liouville CFT and the Cigar

Abstract: We study exact transition amplitudes in certain 2D CFTs — Liouville theory and the SL(2,R)/U(1) coset model describing Witten's 2D black hole. Using bootstrapped conserved currents and a generating functional approach based on canonical transformations, we compute these transitions both recursively and via functional integral representations. The tree-level evaluation of the generating functional reproduces exact results, while providing a diagrammatic framework for loop corrections. We also find that the statistics of Liouville transition elements at higher oscillator levels exhibit level repulsion.

Title: TBA

Abstract: TBA