Ultrasensitive Calorimetric Measurements of the Electronic Heat Capacity of Graphene.
basic_science · Level V
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- Record sourced from PubMed, PMID 34101476.
- Also identified by DOI 10.1021/acs.nanolett.1c01553.
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Abstract
Heat capacity is an invaluable quantity in condensed matter physics and yet has been completely inaccessible in two-dimensional (2D) van der Waals (vdW) materials, owing to their ultrafast thermal relaxation times and the lack of suitable nanoscale thermometers. Here, we demonstrate a novel thermal relaxation calorimetry scheme that allows the first measurements of the electronic heat capacity of graphene. It is enabled by combining a radio frequency Johnson noise thermometer, which can measure the electronic temperature with a sensitivity of ∼20 mK/Hz<sup>1/2</sup>, and a photomixed optical heater that modulates <i>T</i><sub>e</sub> with a frequency of up to Ω = 0.2 THz. This allows record sensitive measurements of the electronic heat capacity <i>C</i><sub>e</sub> < 10 <sup>-19</sup> J/K and the fastest measurement of electronic thermal relaxation time <i>τ</i><sub>e</sub> < 10 <sup>-12</sup> s yet achieved by a calorimeter. These features advance heat capacity metrology into the realm of nanoscale and low-dimensional systems and provide an avenue for the investigation of their thermodynamic quantities.