PGSS 2024

Quantum Materials, for the New Material's Era Beyond Silicon Age

Na Hyun Jo, Professor, Physics Department

We are currently living on the edge of the silicon age, characterized by the rapid growth of the semiconductor industry. Yet, a new class of materials destined to become as familiar as silicon is underway. These materials are so-called quantum materials. In quantum materials, quantum effects manifest over a wide range of energy and length scales and give rise to exotic properties such as superconductivity, exotic magnetism, non-trivial topology, and many more. In this talk, I will present the cutting-edge research in the field of quantum materials, exploring the latest advancements and breakthroughs.

West Hall 335 ---- 12:00h - 13:00h EDT --- 06/06/2024.

Cosmology from Baryon Acoustic Oscillations measurements: 

The first-year Dark Energy Spectroscopic Instrument results

Otávio Alves, Fourth Year, Physics Department

On April 4th, 2024, the Dark Energy Spectroscopic Instrument (DESI) released its first set of cosmological results based on measurements of the baryon acoustic oscillations (BAO) scale in the spatial distribution of galaxies and quasars, and in the Lyman-alpha forest. The measurements constrain the expansion history of the Universe in the redshift range 0.1 < z < 4.16, with implications for studies of dark energy, neutrino cosmology and the Hubble constant. Without assuming any specific prior knowledge, in this talk we will introduce BAO as a cosmological probe, overview how the measurements are done, present the cosmology results described in https://arxiv.org/abs/2404.03002 and discuss some of their main implications, including the 'hints' of dynamical dark energy.

West Hall 335 ---- 12:00h - 13:00h EDT --- 06/13/2024.

Exploring the Dependence of Gas Cooling and Heating Functions on the Incident Radiation Field with Machine Learning: 

David Robinson, Fifth Year, Physics Department

To gravitationally collapse and form a galaxy, a gas cloud needs to release energy by radiative cooling. For this reason, cooling and heating functions, which control gas thermodynamics, play a crucial role in galaxy formation. These functions depend on both gas properties (temperature, density, composition), and the incident radiation field. While they can be computed exactly with existing tools, these tools are computationally expensive and impractical to run on-the-fly in galaxy formation solutions. A traditional approach is to construct tables of pre-computed values and interpolate between points in the table. As an alternative to this, we explore the capacity of machine learning to approximate cooling and heating functions with a generalized radiation field. Specifically, we use the machine learning algorithm XGBoost to predict cooling and heating functions for fixed atomic abundances. We are able to reduce the frequency of the largest ‘catastrophic errors’ compared to an interpolation table approach. We find that the primary bottleneck to increasing accuracy is capturing the dependence on atomic abundances.

West Hall 335 ---- 12:00h - 13:00h EDT --- 06/20/2024.

Optically Induced Electron-Nuclear Spin Interactions:

Unraveling the Relationship between Electrons and Nuclei in Solid State Systems

Estefanio Kesto, Second Year, Physics Department

Compounds are made up of elements; elements are made up of atoms; and atoms are made up of electrons and nuclei. Our group researches electron and nuclear spin interactions in a semiconducting compound known as Gallium Arsenide (GaAs). Utilizing optical techniques, we have the capability of generating, manipulating, and detecting electron spin polarization. Previous work in our lab has found a particular approach that allows us to introduce the electrons to their neighbors: the nuclei family. Introducing the electrons to the nuclei family induces electron-nuclear spin interactions. This interaction process is known as dynamic nuclear polarization (DNP), and in this talk, we will review how our lab induces DNP and its resulting effects on the electron spin dynamics. I’ll first introduce some semiconductor concepts and the optical techniques utilized to generate these effects. Following this, we will delve into the relationship between optically excited electrons and the family of the nuclei. Do the nuclei want to be isolated and left alone, or would they like to make friends with their neighboring electrons?

Let’s explore their relationship and find out together!

West Hall 335 ---- 12:00h - 13:00h EDT --- 07/11/2024.

Higher Spin = Higher Energy: 

Recovering Classical Intuition in Quantum Field Theory

Justin Berman, Third Year, Physics Department

Classically, the larger an object's angular momentum, the higher its kinetic energy. In the hydrogen atom, electrons organize themselves into so-called "orbitals", each of which has quantum numbers associated with the energy level and angular momentum. Similar to the classical case, orbitals at higher energy levels are allowed to have larger angular momentum. However, quantum field theory, the framework we use to describe relativistic quantum physics, appears to allow interactions of particles with arbitrary spin and energy. In my talk, I will show how fundamental consistency conditions, namely requiring that the theory be unitary, local, causal, and Lorentz-invariant, can be used to recover the classical intuition that higher spin requires higher energies.

West Hall 335 ---- 12:00h - 13:00h EDT --- 07/18/2024.

Fragmentation Function variable calculations for heavy flavour quarks at LHCb

Manuel Ramírez García, Second Year, Physics Department

Out of the four fundamental forces in the universe, the Standard Model (SM) of particle physics has been successful in explaining phenomena involving the weak nuclear force, the electromagnetic force, and the strong nuclear force. Quantum Chromodynamics is the  that these colour-charged partons cannot be observed in isolation. For example, at the Large Hadron Collider we have proton-proton collisions where a parton from one of the protons can be ejected; however, this ejected parton is not directly observed. The parton splits into more partons, and this process is repeated until the resulting partons form bound states; as a result, the final state hadrons are (instead) observed. This hadronization process is poorly understood in theory, and experimental constraints, such as the ones we measure at the Large Hadron Collider Beauty experiment, are crucial for a better understanding of this phenomenon.theory that best describes the strong nuclear force. It tells us that through the interaction of the colour-charged quarks and gluons (partons) we get the formation of the nucleons (protons and neutrons) that make up the matter that we observe, as well as a very extensive zoo of hadrons (other composite particles made up of partons). A very important result from experiments is

West Hall 335 ---- 12:00h - 13:00h EDT --- 07/25/2024.

Quantum Sensing Using Hot and Cold Atoms:

Bineet Dash, Fifth Year, Physics Department

Recent advancements in atomic, molecular, and optical (AMO) physics offer exciting prospects for novel quantum sensors with a wide range of sensing objectives. For instance, the wave-like nature of ultracold atoms is exploited in matter wave interferometers for acceleration and rotation sensing, achieving enhanced sensitivities compared to conventional optical interferometers. Another application of atomic quantum sensors is broadband and non-invasive electric field sensing, utilizing highly excited Rydberg states with large electric polarizabilities. In this talk, I will provide an overview of recent developments in these areas and discuss the underlying atomic physics concepts. First, I will present a recent proposal from our group for a new atom interferometer-based rotation sensor featuring a scalable design with a small geometric footprint. In the second part of the talk, I will focus on our work in Rydberg atom-based electric field sensing. I will present progress towards using Rydberg atoms as a non-intrusive, in-situ probe for field diagnostics in delicate environments, such as RF plasma.

West Hall 335 ---- 12:00h - 13:00h EDT --- 08/01/2024.

The Current Status of the Los Alamos Neutron Electric Dipole Moment 

(LANL nEDM) Experiment: 

Felicity Hills, Ninth Year, Physics Department

Sakharov outlined the conditions necessary for the observed baryon asymmetry in our universe, the second of which is the existence of C- and CP-violating interactions. However, the CP-violating interactions in SM baryogenesis are inconsistent with the degree of baryon asymmetry we observe. In this talk, I will discuss how measuring the neutron electric dipole moment (nEDM) searches for this "missing" CP-violation, how the nEDM is measured, and how the LANL nEDM experiment aims to improve the sensitivity of nEDM measurements to ~3x10^-27 e-cm.

West Hall 335 ---- 12:00h - 13:00h EDT --- 08/08/2024.

Role of Spectral methods in climate, ocean and atmosphere science: 

Avik Mondal, Sixth Year, Physics Department

In response to climate change, climate science has become one of the fastest-growing fields of science, focused on better predicting future climate conditions, mitigating disasters, and reducing the anthropogenic drivers of climate change. While the field is inherently interdisciplinary, many don't appreciate the contributions that physics and physicists can make to climate science, including physicists themselves. In this talk, I want to give a quick overview of climate physics, starting with the history of climate physics, including where you may have encountered it in your undergraduate classes. I will then briefly cover the direction the field has been moving in recent decades, Finally, I will end by talking about my project, which focuses on understanding air-sea interactions using diagrammatic (think Feynman) representations of energy and heat fluxes.

West Hall 335 ---- 12:00h - 13:00h EDT --- 08/15/2024.