Abstract

Since the discovery of graphene, research on two-dimensional (2D) materials has become a central focus of condensed matter physics. While an enormous number and variety of investigations of their electrical, optical, and mechanical properties have been undertaken, their thermal properties remain comparatively underexplored, despite the importance for understanding low-energy excitations and phase transitions. Here, we introduce an extension of the 3ω method thermal measurement technique to the 2D limit of materials. We develop analytical models of thermal transport in the 3ω geometry with boundary conditions tailored for suspended 2D flakes. We then experimentally confirm the feasibility of this approach in a quasi-2D system, namely suspended silicon nitride membranes with the aspect ratio of typical 2D samples; and subsequently apply the modified 3ω method to representative materials including thin (~10s of nm thick) hBN, FePS₃, and α-RuCl₃. For hBN, we extract thermal conductivity values consistent with previous reports on bulk samples. In FePS₃, clear signatures of the antiferromagnetic phase transition near 120 K are observed in both the specific heat and thermal conductivity. And for α-RuCl₃, the measured thermal properties are found to deviate significantly from earlier studies on pristine bulk samples, which we attribute to stacking faults introduced during device fabrication. These initial experimental successes are a strong motivation for future measurements on monolayer samples. Overall, these results establish our modified 3ω approach as a practical tool for investigating the thermal properties of a broad range of 2D materials.

Committee Chair

Erik Henriksen

Committee Members

Kelly Powderly; Li Yang; Shankar Mukherji; Sheng Ran

Degree

Doctor of Philosophy (PhD)

Author's Department

Physics

Author's School

Graduate School of Arts and Sciences

Document Type

Dissertation

Date of Award

4-27-2026

Language

English (en)

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