The 3ω method works by depositing a thin metal heater/thermometer onto the sample. An AC current is passed through the metal film at frequency ω, causing it to heat up and cool down at a frequency of 2ω. This periodic heating induces a temperature oscillation, which in turn generates a voltage signal at a frequency of 3ω. By analyzing the amplitude and phase of this 3ω signal, researchers can deduce the thermal conductivity of the sample.
