Faculty Sponsor: Francis Starr
Jack Gagliardi
Jack Gagliardi is a rising junior (’28) majoring in Physics and Astronomy, doing research at Wesleyan in a Computational Physics Group. Over the past year, he has studied the Moire Material graphene and its unique mechanical properties. Outside of physics, he enjoys playing basketball with friends.
Abstract: Two-dimensional materials such as graphene can acquire entirely new mechanical and electronic properties when two layers are stacked with a small relative twist angle, producing a moiré superlattice. Much of the current interest in moiré materials is concentrated in this small-angle regime, where interesting properties, such as superconductivity, emerge near a so-called “magic angle.” Here I examine how twist angle affects the Young’s modulus of bilayer graphene at ambient temperatures using large-scale molecular dynamics simulations driven by a machine-learned interatomic potential (ACE, with a van der Waals correction), run on GPU nodes of Wesleyan’s Swallowtail computing cluster. Unlike most prior studies, which model these systems at the near-zero-kelvin regime, our simulations run at ambient, room-temperature conditions, capturing how thermal motion shapes the material’s structure and response. Across a multitude of twist angles spanning 0° to just over 5°, we extract Young’s modulus from the linear region of simulated stress–strain curves. We find that Young’s modulus follows a U-shaped trend with twist angle, reaching a minimum near 1.3°–1.5°, a small-angle feature not resolved by studies that focus on larger twist angles. We connect this behavior to the underlying thermal rippling that is absent from zero-temperature calculations. These results suggest that finite-temperature effects meaningfully reshape the mechanical response of moiré materials precisely in the small-angle regime where their most interesting physics occurs.
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