The Nanoscale and Quantum Phenomena Institute Seminar series presents Abraham Mojarro, Chase Cartwright, and Collin Collins, Ohio University, on February 27 at 4:10 p.m. Seminars are held in ***WALTER 135*** and virtually on Teams. Refreshments provided.

Where is Majorana? Looking for a particle (physicist) in a kagome superconductor
Abraham Mojarro, Graduate Student, Ohio University
The disappearance of Ettore Majorana in 1938 in the Mediterranean Sea remains an unsolved mystery. Yet, his legacy endures through the concept of Majorana fermions—hypothetical particles that are their own antiparticles, with implications from the unification of the fundamental forces to exotic states of matter. Interestingly, Majorana fermions emerge as quasiparticles in topological superconductors, where they hold promise for fault-tolerant quantum computing. However, the mystery remains, where can we find Majorana (particles)? In this talk, I will present our recent work on topological superconductivity in kagome materials, where a simple singlet s-wave pairing potential combined with Rashba spin-orbit (RSO) interaction leads to Majorana edge states. When time-reversal symmetry (TRS) is preserved, the system's topology is determined by a Z2 invariant, allowing for topological, nodal, and trivial superconducting phases depending on system parameters. Furthermore, introducing a TRS-breaking chiral flux phase leads to chiral Majorana edge states characterized by a Chern number. We show that the interplay of RSO interaction and superconductivity enables topological phases with distinct Chern numbers. Our results reveal that even a conventional s-wave superconductor can host Majorana fermions, opening new directions in the search for Majorana fermions in the recently discovered kagome superconductors and providing a promising platform for studying topological superconductivity.

Image segmentation methods for automated morphological analysis of organoids
Chase Cartwright, Graduate Student, Ohio University
Organoids — three-dimensional, self-organized cell cultures derived from stem cells — are a powerful platform for the study of diseases and their possible treatments. Organoids are typically created by first growing spheroids — three dimensional cultures of only a single cell type — of induced pluripotent stem cells (iPSCs). In a separate work, we are studying the early growth of several hundred of those cultures, resulting in tens of thousands of microscopy images. We are using computer vision and machine learning techniques to automatically measure the size and shape of the developing spheroids.

Here, we report on the performance of several of these tools by testing them on a subset of the data and comparing with the results of manual image segmentation. We show that existing segmentation tools can be improved both with task-specific training data and by combining them with other, general-purpose segmentation tools, and we compare the impact of these two enhancements.

Characterizing Dynamical Heterogeneity in a Supercooled Glass-Forming Diatomic Liquid
Collin Collins, Undergraduate Student, Ohio University
We use molecular dynamics simulations to investigate a 3D supercooled liquid of diatomic molecules interacting via the Lennard-Jones potential. We simulate the system for temperatures approaching the glass transition and verify that the system does not crystallize by measuring local order parameters and correlation functions. We use the overlap to study the translational dynamics and introduce a rotational overlap measure to examine the orientational dynamics as the system slows down. We investigate the heterogeneous dynamics for both types of degrees of freedom and characterize the geometry of the heterogeneous regions.