The 3ω (three-omega) method is an advanced experimental technique primarily used to measure the thermal conductivity of materials at the nanoscale. It involves applying an alternating current (AC) at a frequency, ω, to a thin metal film deposited on the sample. This generates heat at a frequency of 2ω due to joule heating, and the resulting temperature oscillations are detected at a frequency of 3ω. The amplitude and phase of the 3ω voltage provide information about the thermal properties of the material.
