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Main Authors: Metzger, Cyril, Emser, Alec L., Rose, Brendon C., Lehnert, Konrad W.
Format: Preprint
Published: 2025
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Online Access:https://arxiv.org/abs/2512.24539
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author Metzger, Cyril
Emser, Alec L.
Rose, Brendon C.
Lehnert, Konrad W.
author_facet Metzger, Cyril
Emser, Alec L.
Rose, Brendon C.
Lehnert, Konrad W.
contents We present experimental evidence of a thermally-driven amplitude-frequency nonlinearity in a thin-film quartz phononic crystal resonator at millikelvin temperatures. The nonlinear response arises from the coupling of the mechanical mode to an ensemble of microscopic two-level system defects driven out of equilibrium by a microwave drive. In contrast to the conventional Duffing oscillator, the observed nonlinearity exhibits a mixed reactive-dissipative character. Notably, the reactive effect can manifest as either a softening or hardening of the mechanical resonance, depending on the ratio of thermal to phonon energy. By combining the standard TLS theory with a thermal conductance model, the measured power-dependent response is quantitatively reproduced and readout-enhanced relaxation damping from off-resonant TLSs is identified as the primary mechanism limiting mechanical coherence. Within this framework, we delineate the conditions under which similar systems will realize this nonlinearity.
format Preprint
id arxiv_https___arxiv_org_abs_2512_24539
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle TLS-induced thermal nonlinearity in a micro-mechanical resonator
Metzger, Cyril
Emser, Alec L.
Rose, Brendon C.
Lehnert, Konrad W.
Quantum Physics
Mesoscale and Nanoscale Physics
We present experimental evidence of a thermally-driven amplitude-frequency nonlinearity in a thin-film quartz phononic crystal resonator at millikelvin temperatures. The nonlinear response arises from the coupling of the mechanical mode to an ensemble of microscopic two-level system defects driven out of equilibrium by a microwave drive. In contrast to the conventional Duffing oscillator, the observed nonlinearity exhibits a mixed reactive-dissipative character. Notably, the reactive effect can manifest as either a softening or hardening of the mechanical resonance, depending on the ratio of thermal to phonon energy. By combining the standard TLS theory with a thermal conductance model, the measured power-dependent response is quantitatively reproduced and readout-enhanced relaxation damping from off-resonant TLSs is identified as the primary mechanism limiting mechanical coherence. Within this framework, we delineate the conditions under which similar systems will realize this nonlinearity.
title TLS-induced thermal nonlinearity in a micro-mechanical resonator
topic Quantum Physics
Mesoscale and Nanoscale Physics
url https://arxiv.org/abs/2512.24539