Rice University Applied Physics Program

Masters Thesis Defense: Wen-Hua Wu
Date & Time: Friday, June 12th | 9:00 - 11:00 AM
Location: SST 301A

Host Department: ECE
Advisor: Junichiro Kono
Committee: Junichiro Kono, Songtao Chen, Kaden Hazzard

Title: Floquet-Driven Superradiant Phase Transition in Ultrastrongly Coupled Landau Polaritons

Abstract
This thesis investigates light–matter interactions in condensed matter through Floquet engineering and terahertz spectroscopy. On the theoretical side, we propose a framework for a Floquet-driven superradiant phase transition (SRPT) in Landau polaritons. By temporally modulating the magnetic field, we circumvent the Thomas–Reiche–Kuhn sum rule no-go theorem, enabling a second-order phase transition and photon condensation. We evaluate the experimental implementation of Floquet-driven SRPTs, highlighting the role of thermal effects and the necessity of metasurfaces for efficient field modulation. These results advance the fields of cavity quantum electrodynamics and many-body Floquet dynamics. Additionally, we utilized terahertz time-domain spectroscopy to study the quantum spin liquid candidate α-RuCl3. High-field measurements in the Voigt geometry reveal broadening of the absorption line, offering key evidence for the quantum spin liquid phase. We also explored ultrafast carrier dynamics in a PbTe thin film and identified nonlinearities in GaAs-based Landau polaritons, where spatial inhomogeneities and nonparabolicity invalidate the standard linear bosonic model.

Zoom link
https://zoom.us/j/95270116497?pwd=aBNECf0z1CZj5HPpC9vM0GblGixPFW.1

Congratulations to DOCTOR Shengjie Yu on a successful defense!

Doctoral Thesis Defense: Shengjie Yu
Date & Time: June 9, 2026, 1:00 PM
Location: Brockman Hall for Physics BRK 200

Host Department: ECE
Advisor: Prof. Junichiro Kono
Committee: Prof. Geoff Wehmeyer, Prof. Douglas Natelson, Prof. Matteo Pasquali

Title: Electronic Transport in Aligned Carbon Nanotube Assemblies

Abstract:
Carbon nanotubes (C**s) are widely used to study quantum transport in low-dimensional systems because of their one-dimensional electronic structure and long phase-coherence lengths. In practical materials, however, C**s assemble into bundles, fibers, and aligned films, where intertube coupling, disorder, anisotropy, and current-path distribution reshape transport signatures. This dissertation examines how phase-coherent transport appears across this hierarchy in macroscopic CNT fibers, exfoliated CNT bundles, and aligned CNT films, using temperature-dependent transport, magnetotransport, nonlocal measurements, and angular-dependent magnetotransport.

In highly aligned CNT fibers, the direct observations are metallic high-temperature transport and a pronounced positive low-temperature magnetoconductance with field dependence characteristic of weak localization (WL). These measurements show that phase-coherent corrections remain observable in a macroscopic CNT conductor. Fits to the magnetoconductance also show that single-dimensional WL models are insufficient. An effective mixed-dimensional interpretation, combining bundle-scale quasi-one-dimensional coherence with a more extended diffusive contribution, provides a constrained phenomenological description of the fiber response.

Individual CNT bundles exfoliated from the fibers reveal WL-like low-field magnetoconductance, reproducible universal conductance fluctuations (UCF), and nonlocal field-dependent signals over micron-scale separations. Comparing these probes gives the central conceptual result: the WL field scale, UCF amplitude, and nonlocal response define different operational coherence scales. The corresponding interpretation is trajectory dependent, with short, flux-sensitive diffusive loops coexisting with a subset of pathways that remain correlated over longer portions of the bundle.

Aligned CNT films show how current direction, channel length, and field orientation control transport in a planar anisotropic network. Perpendicular transport is hopping-dominated and exhibits a low-temperature dimensional crossover, whereas parallel transport is more conductive and shows low-field magnetotransport compatible with a phenomenological WL-like description. Long-channel devices average over network anisotropy more strongly, while shorter channels make directional magnetotransport more visible; angular-dependent magnetotransport further distinguishes angularly averaged response from anisotropic flux sensitivity.

Overall, the thesis shows that phase-coherent signatures remain experimentally observable in aligned CNT assemblies, but their interpretation depends on the observable and measurement geometry.

Zoom link:
https://riceuniversity.zoom.us/j/92604535244?pwd=vwzT4vkEbkPaMpYsQ6LrBcbXmBawOU.1

Meeting ID: 926 0453 5244
Passcode: 466907

SCI Applied Physics social and welcome to our NTU Research Experience International Students (REIS) at Rice University Valhalla 🦉👐💙🍻!

APP students, faculty, and alumni are invited to join SCI members as we welcome visiting summer exchange students from NTU Singapore. There will be pizza and an open tab at Valhalla! Please see email to RSVP.

Earlier this month, the APP community gathered for a special dinner to honor our wonderful Applied Physics Committee members. The night doubled as a celebration for the birthday of faculty member, Emilia Morosan!

APGSA is organizing a practice master's thesis defense for Albert Wu (APP). All APP PhD students are invited to attend, enjoy free lunch, and provide structured feedback using short evaluation rubrics.

Rice researchers have proposed a new platform for detecting axion dark matter called SQWARE (Semiconductor-Quantum-Well Axion Radiometer Experiment), introducing a quantum semiconductor approach to probing one of the biggest mysteries in physics.
Led by Rice graduate student Jaanita Mehrani, the project combines photonics, condensed matter physics and high-energy physics to establish the theoretical foundation for a new dark matter detection initiative.