High-Bandwidth, Variable-Resistance Differential Noise Thermometry

TL;DR

This paper introduces a high-bandwidth differential noise thermometry technique suitable for mesoscopic devices with variable impedance, enabling fast, precise temperature measurements across a broad resistance range.

Contribution

It presents a novel differential noise measurement method with impedance matching and cryogenic amplifiers, achieving high-frequency thermometry with improved accuracy and speed.

Findings

Achieved noise measurement in 120-250 MHz range

Calibrated temperature with 650 mK precision at 10 K

Measured thermal conductivity in bilayer graphene across regimes

Abstract

We develop Johnson noise thermometry applicable to mesoscopic devices with variable source impedance with high bandwidth for fast data acquisition. By implementing differential noise measurement and two-stage impedance matching, we demonstrate noise measurement in the frequency range 120-250 MHz with a wide sample resistance range 30 {\Omega}-100 k{\Omega} tuned by gate voltages and temperature. We employ high-frequency, single-ended low noise amplifiers maintained at a constant cryogenic temperature in order to maintain the desired low noise temperature. We achieve thermometer calibration with temperature precision up to 650 mK on a 10 K background with 30 s of averaging. Using this differential noise thermometry technique, we measure thermal conductivity on a bilayer graphene sample spanning the metallic and semiconducting regimes in a wide resistance range, and we compare it to the electrical conductivity.