Normal Metal Hot-Electron Nanobolometer with Johnson Noise Thermometry Readout

TL;DR

This paper analyzes a normal-metal hot-electron nanobolometer using Johnson Noise Thermometry, predicting high sensitivity (NEP ~ 10^{-20} - 10^{-19} W/Hz^{1/2}) at cryogenic temperatures for THz detection.

Contribution

It introduces a normal-metal nano-HEB with Johnson Noise Thermometry readout capable of operating at various cryogenic temperatures with high sensitivity.

Findings

Expected NEP of ~10^{-20} - 10^{-19} W/Hz^{1/2} at 50-100 mK.

Single low-noise amplifier can read hundreds of nano-HEBs.

Sensitivity remains fairly constant over 10 GHz readout bandwidth.

Abstract

The sensitivity of a THz hot-electron nanobolometer (nano-HEB) made from a normal metal is analyzed. Johnson Noise Thermometry (JNT) is employed as a readout technique. In contrast to its superconducting TES counterpart, the normal-metal nano-HEB can operate at any cryogenic temperature depending on the required radiation background limited Noise Equivalent Power (NEP). It does not require bias lines; 100s of nano-HEBs can be read by a single low-noise X-band amplifier via a filter bank channelizer. The modeling predicts that even with the sensitivity penalty due to the amplifier noise, an NEP ~ 10$^{-20}$ - 10$^{-19}$ W/Hz$^{1/2}$ can be expected at 50-100 mK in 10-20 nm thin titanium (Ti) normal metal HEBs with niobium (Nb) contacts. This NEP is fairly constant over a range of readout frequencies ~ 10 GHz. Although materials with weaker electron-phonon coupling (bismuth, graphene) do not improve the minimum achievable NEP, they can be considered if a larger than 10 GHz readout bandwidth is required.