Superconductivity in Spin-orbit-coupled Rhombohedral Trilayer Graphene
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yang-jxyang-phd-physics-2026-thesis.pdf
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60.58 MB
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Author(s)
Yang, Jixiang
Advisor(s)
Ju, Long
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
Rhombohedral-stacked graphene has recently emerged as a two-dimensional quantum material platform for studying electron correlation, topology, and superconductivity. However, the role of another key ingredient of modern condensed matter physics, spin–orbit coupling (SOC), remains largely unexplored in this system, as the intrinsic SOC is negligibly weak in pristine graphene. In this thesis, I systematically studied the impact of SOC, induced by proximitized transition-metal dichalcogenides (TMD) layers, on the electronic properties of rhombohedral trilayer graphene (RTG). In particular, I focused on its interplay with superconductivity in such systems. Compared to bare RTG, the electron-doped superconducting state SC3 is enhanced and two new hole-doped superconducting states, SC4 and SC5, are induced in TMD-proximitized RTG devices. Surprisingly, the original superconducting state SC1 in bare RTG is strongly suppressed in the presence of TMD — opposite to the effect of SOC on all other graphene superconductivity. I then carefully examined these SOC-induced superconducting states and found that SC5 exhibits highly unconventional behavior under in-plane magnetic fields: instead of being suppressed, SC5 is progressively enhanced with increasing in-plane magnetic fields. It survives up to B_|| = 8.835 T, limited solely by instruments, corresponding to a record-high Pauli-limit violation ratio of at least 80 among all known superconductors. These data suggest that SC5 experiences a canting crossover from an Ising-type to a spin-polarized superconductor as in-plane magnetic fields increase. Finally, I will also discuss a few other novel discoveries in this system, including the electron-interaction-driven nematicity in the superconducting state SC3 and SC4, the emergence of a new isospin-symmetry-broken state named the three-quarter metal (TQM), and the signatures of a possible quantum spin Hall state. These findings demonstrate SOC as a powerful tuning knob for manipulating electronic properties in rhombohedral graphene families and establish spin-orbit-coupled RTG as a new promising venue for exploring and utilizing exotic quantum phases.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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