Development of high frequency and wide bandwidth Johnson noise thermometry

TL;DR

This paper introduces a high-frequency, wide bandwidth Johnson noise thermometry technique capable of measuring nanoscale thermal transport with high sensitivity across a broad temperature range, revealing deviations from classical laws.

Contribution

It presents a novel room-temperature radiometer with GHz operation and enhanced sensitivity for nanoscale thermal measurements, extending Johnson noise thermometry capabilities.

Findings

Measured thermal conductance of graphene device from 3 to 300 K.

Observed a T^4 power law deviation from Wiedemann-Franz law above 100 K.

Achieved 5.5 mK sensitivity in 1 second of integration.

Abstract

We develop a high frequency, wide bandwidth radiometer operating at room temperature, which augments the traditional technique of Johnson noise thermometry for nanoscale thermal transport studies. Employing low noise amplifiers and an analog multiplier operating at 2~GHz, auto- and cross-correlated Johnson noise measurements are performed in the temperature range of 3 to 300~K, achieving a sensitivity of 5.5~mK (110 ppm) in 1 second of integration time. This setup allows us to measure the thermal conductance of a boron nitride encapsulated monolayer graphene device over a wide temperature range. Our data shows a high power law (T$^{\sim4}$) deviation from the Wiedemann-Franz law above T$\sim$100~K.