Measuring two-level tunneling systems in the ultrastable organic glass 2TNATA

ecause decoherence from ubiquitous two-level-tunneling-systems (TLSs) is recognized as a source that limits the quantum coherence time in superconducting qubits, there is a practical interest in developing low-TLS dielectrics. The fact that low-TLS amorphous silicon and ultrastable glasses both (a) are grown via vapor deposition onto substrates held at specific temperatures and (b) exhibit unusual physical properties has led to speculation that there is a connection between ultrastability and suppression of TLSs in amorphous dielectric materials. In light of heat capacity measurements on other ultrastable organic glasses that are both suggestive of such a link but with limited resolution, we set to measure TLS levels via internal friction measurements of the organic glass 2TNATA, grown in an ultrastable configuration on silicon double-paddle-oscillator resonators that are designed for thin film measurements. Although we do not find a substantial reduction in TLS density, we do observe systematic and repeatable changes between the ultrastable and ordinary glass configurations of this material, including an internal friction peak at 16K that is shifted to higher temperatures in the ordinary glass configuration. We demonstrate that such mechanical measurements can be a useful addition to the ultrastable glass investigative toolkit in addition to their use for high resolution TLS measurements.