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MSE PhD Prospectus Defense: Jing Tang

TITLE: Spectroscopic and Data-Driven Approaches to Twisted and Multiferroic van der Waals Materials

ADVISOR: Xi Ling Chemistry

COMMITTEE: Wanzheng Hu Physics, Kevin Smith Physics, Anna Swan ECE Physics, Sahar Sharifzadeh ECE

ABSTRACT: Two-dimensional (2D) materials exhibit a wide range of emergent properties when engineered at the atomic scale, particularly through stacking, twisting, and external stimuli. My research focuses on uncovering new physical phenomena in twisted and multiferroic van der Waals (vdW) materials using a combination of spectroscopy techniques, first-principles calculations, and data-driven approaches. In my first project, I developed a machine learning-assisted low-frequency Raman spectroscopy technique to precisely determine the twist angle in few-layer MoS₂. By integrating a neural network model with experimental data and an angle-dependent linear chain model, I demonstrated a noninvasive method to probe interlayer coupling and symmetry evolution in twisted bilayer and trilayer systems. This work is published on Journal of Raman Spectroscopy. In my second project, I investigated the multiferroic vdW CuCrP₂S₆ system, identifying multiple temperature-driven phase transitions and strong magnetoelastic coupling via temperature- and polarization-resolved Raman spectroscopy. This work is published on The Journal of Physical Chemistry Letters. Moving forward, my future research will explore emerging behaviors in twisted magnetic (e.g. NiPS3) and multiferroic (e.g. ABP2X6, where A and B are transition metals and X is a chalcogen such as sulfur or selenium) 2D systems, with a particular focus on interlayer interactions and tunable (e.g., via electric or magnetic fields) properties. These directions aim to advance our understanding of quantum materials and develop intelligent methodologies for their study and design.