Quantum lock-in amplifier phonon detectors

Informazioni relative al progetto

Q-LAMP

ID dell’accordo di sovvenzione: 101155102

DOI

10.3030/101155102

Progetto chiuso

Data della firma CE 19 Marzo 2024

Data di avvio 1 Aprile 2024

Data di completamento 31 Marzo 2026

Finanziato da

• Marie Skłodowska-Curie Actions (MSCA)

Costo totale

Nessun dato

Contributo UE

€ 199 694,40

Coordinato da

AALTO KORKEAKOULUSAATIO SR
Finland

Periodic Reporting for period 1 - Q-LAMP (Quantum lock-in amplifier phonon detectors)

Periodo di rendicontazione: 2024-04-01 al 2026-03-31

Sintesi del contesto e degli obiettivi generali del progetto

Phonons, the quantum excitations of atomic vibrations, are central to heat transport, superconductivity, and many quantum technologies [Phys. Rev. B, 109, 144303, (2024)]. Yet standard phonon probes such
as Raman spectroscopy mainly reveal phonon frequency and intensity, while giving limited access to phase and time-domain dynamics [ACS Nano, 14, 28–117, (2019)]. This restricts the study of coherent
phonon processes in quantum materials.

Q-Lamp addresses this gap by developing a quantum lock-in amplifier for phonon detection. The goal is a sensor that can detect both acoustic phonons, linked to strain, and thermal phonons, linked
to dissipation and heating, within one platform [Nat. Commun., 15, 4979, (2024); Nat. Photonics, 5, 222–229, (2011)]. Existing technologies usually detect only one of these channels, for example thermal phonons with transition-edge sensors or mechanical phonons with superconducting qubit-acoustic
devices [Phys. Rev. Appl., 22, 024051, (2024); Phys. Rev. B, 97, 205443, (2018)].

The project uses suspended two-dimensional NbSe2 as the active material. In this system, strain can tune superconductivity through changes in electron-phonon coupling, while thermal effects modify vortex motion and energy loss [Nat. Commun., 12, 2314, (2021); Nano Lett., 18, 2623–2629, (2018); Phys. Rev. B, 93, 134508, (2016)]. Suspension is essential because it increases both mechanical compliance and thermal isolation.

To support device design, the project combines two theoretical tools. Density functional theory with Electron-Phonon Wannier calculations links strain to electron-phonon coupling and critical temperature[Computer Physics Communications, 209, 116–133, (2016); Phys. Rev. B, 76, 165108, (2007); Computer Physics Communications, 185, 2309–2310, (2014)]. Time-dependent Ginzburg-Landau simulations linked to heat diffusion describe thermal feedback and vortex dynamics [Supercond. Sci. Technol., 31, 055007, (2018); Phys. Rev. Lett., 40, 1041–1044, (1978)]. Together, these methods guide the design of a dual-mode quantum phonon detector with relevance for sensing and dark matter searches [Phys. Rev. D, 109, 023010, (2024)].

Lavoro eseguito dall’inizio del progetto fino alla fine del periodo coperto dalla relazione e principali risultati finora ottenuti

Q-Lamp has established suspended NbSe2 as a promising platform for controllable superconductivity under combined strain and thermal modulation [arXiv:2511.05763 (2025), main work]. The work shows that
suspension is not only a fabrication choice but a functional route to stronger coupling between mechanical deformation, heating, and the superconducting state.

A first achievement is the demonstration of a practical route to strain-controlled superconductivity. Electrostatic deformation in suspended structures provides reversible tuning of superconducting
behaviour, in line with published evidence that thin NbSe2 is highly sensitive to strain, thickness, and electron-phonon coupling.

A second achievement is the identification of enhanced thermal response in suspended devices. Removing the supporting substrate reduces heat sinking and mechanical clamping, which strengthens local
heating effects and makes thermal-superconducting coupling easier to observe. With the thermal couping, we achieved the observation and interpretation of multi-stage hysteresis and negative differential resistance.
These effects are consistent with strong thermal feedback and non-equilibrium superconducting transport, and they indicate access to multiple dissipative states that may be useful for sensing and signal amplification [Sci. Adv., 6, eaba1377, (2020); Nat. Phys., 15, 947–953, (2019); Phys. Rev. B, 93, 134508, (2016)].

A fourth achievement is the development of a combined modelling strategy. Microscopic DFT/EPW calculations quantify how strain changes electron-phonon coupling and critical temperature, while TDGL-based thermal simulations reproduce vortex-driven transport behaviour and heating effects. This creates
a direct link between material design and device performance. The code of TDGL coupling with thermal is uploaded in https://github.com/fangrh/TDGLThermal.git

Progressi oltre lo stato dell’arte e potenziale impatto previsto (incluso l’impatto socioeconomico e le implicazioni sociali più ampie del progetto fino ad ora)

The current state of the art in phonon sensing is fragmented. Existing platforms usually target either thermal phonons, as in transition-edge sensors, or mechanically coupled phonons, as in superconducting
qubit-acoustic systems [Phys. Rev. Appl., 22, 024051, (2024); Phys. Rev. B, 97, 205443, (2018)]. In parallel, advanced modelling tools exist for electron-phonon coupling and superconducting transport,
but they are often applied separately rather than as one design workflow [Computer Physics Communications, 209, 116–133, (2016); Computer Physics Communications, 291, 108799, (2023)].

Q-Lamp goes beyond this state of the art by bringing these elements together in one suspended superconducting platform. Suspended NbSe2 is used not only as a sensitive material, but as a device
architecture in which strain and thermal effects can both modulate superconductivity [Nano Lett., 18, 2623–2629, (2018); arXiv:2511.05763 (2025)]. This creates a route toward dual-mode phonon detection
within one system rather than two separate detector classes.

The project also goes beyond the state of the art by linking material-level and device-level modelling in a single framework. Q-Lamp combines DFT/EPW calculations for strain-dependent electron-phonon
coupling with TDGL-based thermal transport simulations for vortex dynamics and dissipation [Computer Physics Communications, 209, 116–133, (2016); Supercond. Sci. Technol., 31, 055007, (2018)]. This
improves predictive design and reduces reliance on trial-and-error optimization.

Finally, Q-Lamp treats nonlinear superconducting behaviour as a functional advantage. Hysteresis, multistability, and negative differential resistance are not only signatures of complex transport, but potential
resources for signal amplification and sensitive readout [Sci. Adv., 6, eaba1377, (2020); Nat. Phys.,15, 947–953, (2019)]. These advances open applications in quantum sensing, studies of electron-phonon
coupling in two-dimensional materials, and phonon-based dark matter detection [Nat. Photonics, 5,222–229, (2011); Phys. Rev. D, 109, 023010, (2024)].