Condensed Matter, Nuclear, & Plasma Parallel Talks

Nanostructured materials can exhibit thermal and elastic properties unachievable in bulk systems due to the increased influence of surfaces and interfaces on the length scales intrinsic to energy carriers such as phonons and electrons. Fully characterizing the thermal, elastic, and structural properties of these nanostructured semiconductor materials is crucial for developing new materials with tunable properties for applications in next-generation nanoelectronics and energy efficient devices. However, experimentally accessing or theoretically predicting the properties of complex nanostructured materials at these length scales is challenging.

To probe the nanoscale thermal and elastic properties of semiconductors, we developed an experimental platform that utilizes ultrafast, coherent EUV beams generated via high harmonic generation in a pump-probe scatterometry technique. Nickel grating transducers fabricated on the samples are impulsively heated using an infrared pump laser pulse, launching surface acoustic waves (SAW) and heat into the sample. These dynamics are probed using EUV scatterometry with sub-30 nm spatial and femtosecond temporal resolution, enabling nondestructive extraction of thermal, elastic, and structural properties.

As an application we characterize the properties of silicon metalattices—artificial 3D solids, periodic on the sub-100 nm length scale. By comparing measured frequencies of the SAWs to different finite element models of the metalattice structure, we can extract the structural and mechanical properties of  this complex, nanostructured material, including the porosity and metalattice film thickness. With the same measurement, we observe unexpected Fourier-like heat flow with an ultralow apparent thermal conductivity. Finally, we verify these results through modeling and 3D electron tomography.

We demonstrate that modest magnetic fields (< 0.1 T), when applied during high-temperature crystal growth, can profoundly alter the structural and electronic ground state of a  spin-orbit-coupled, antiferromagnetic trimer lattice. Using BaIrO3 as a model system, we show  that magneto-synthesis, a field-assisted synthesis approach, stabilizes a structurally compressed,  metastable metallic phase that cannot be accessed through conventional synthesis routes. This  field-tailored phase exhibits a shortened Ir-Ir bond distance, reduced lattice distortion, and  suppressed magnetic order, culminating in a robust insulator-to-metal transition. Electrical  resistivity drops by up to four orders of magnitude, while the low-temperature specific heat reveals  a substantial enhancement in the Sommerfeld coefficient (γ ≈ 37 mJ/mol·K2), consistent with the  emergence of a highly correlated metallic state. First-principles calculations confirm that the field stabilized phase lies significantly above the ground state in energy, underscoring its metastable  nature. These findings establish magneto-synthesis as a powerful new pathway for accessing non-equilibrium quantum phases in complex oxides and other strongly correlated materials.

The SALER experiment searches for beyond-Standard-Model (BSM) electroweak physics by measuring eV scale nuclear recoils from decaying short-lived isotopes using cryogenic quantum sensors. To achieve less than 10 eV full width at half max (FWHM) resolution during measurement, these cryogenic sensors require magnetic shielding due to their susceptibility to magnetic interference. However, an external rare isotope ion beam needs to reach the cryogenic sensors once at operating temperature. To achieve this, we have designed and tested a pivoting magnetic shield. In this presentation, I will show our methodology, testing, and initial results.

My research involves utilizing FEA and CFD programs to simulate explosive lenses in order to generate hypersonic projectiles, which can then be utilized to compress and ignite a fusion target (or could be used as an initial compression strategy for things that are more difficult to fuse, like deuterium). This research is all focused around creating cheap high energy fusion neutron sources which are lightweight, cheap, and relatively safe compared to other options. I currently use Ansys Mechanical FEA to simulate the explosive charges and the projectile impacts, but I am running into limitations of software as it appears I am getting energy out of nowhere. Cheap high energy neutron sources enable a lot of very cool technology, we could fission depleted uranium for energy, transmute nuclear waste, or a variety of other useful technologies.

The Parker Solar Probe is a NASA spacecraft that orbits the Sun, passing within 10 solar radii at closest approach. It gathers data about particles and electromagnetic fields in the heliosphere, helping us gain a better understanding of the near-Sun solar wind. The ion acoustic wave is a type of compressional plasma wave that propagates along magnetic field lines. Frequency-dispersed ion acoustic waves were recently discovered by the Solar Probe in the near-Sun solar wind, appearing in short bursts that rise or fall in tone. These waves are likely triggered by proton beams, but the source of the accelerated ions is unknown. This same acceleration process is active throughout the near-Sun solar wind, and could play a significant role in the acceleration and heating of the solar wind. One theory suggests that these proton beams are accelerated by steepened Alfvén waves. Alfvén waves are plasma waves in which ions respond to magnetic field line fluctuations. Wave steepening occurs when nonlinear effects cause wave speed to depend on amplitude, distorting the shape like ocean waves starting to break as they approach shore. In my project, I looked for indicators of steepened Alfvén waves in Solar Probe data to see if there is a correlation with ion acoustic wave detections. No strong correlation was found between any of the explored indicators of steepened Alfvén waves and the presence of ion acoustic waves.  Therefore, these observations do not support the theory that proton beams near the Sun are generated by steepened Alfvén waves.

A linear optical interferometer for measuring the thickness of a laser-ionized plasma filament will be presented. This plasma filament will serve as the plasma source in plasma wakefield accelerator (PWFA) experiments to be carried out at SLAC National Accelerator Laboratory’s FACET-II facility. The diagnostic is based on a design by colleagues at UCLA [1] and compares the relative phase delay of a femtosecond probe laser pulse to that of a twin reference pulse, both which travel along the same path. The twin pulses are produced in a birefringent crystal, which imposes a picosecond-scale delay between the two pulses. The plasma-producing high-intensity laser pulse is fired between the leading reference pulse and the trailing probe pulse. The reference and probe pulses are then recombined in a second birefringent crystal, allowing for a measurement of their mutual interference and thereby an inference of the plasma filament's thickness & density profile. By optimizing the detection hardware and electronics, we expect to have sufficient sensitivity to measure plasma filaments with a thickness of order 100 µm and densities as low as 10^16 cm-3.

[1] Z. Nie, et al., “Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements”, Optics Express 30 25696 (2022)