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Abstract The next generation of bolometric experiments searching for rave events, in particular for the neutrino-less double beta decay, needs fast, high-sensitivity and easy-to-scale cryogenic light detectors. The CALDER project (2014–2020) developed a new technology for light detection at cryogenic temperature. In this paper we describe the achievements and the final prototype of this project, consisting of a $$5\times 5~\hbox {cm}^2$$ 5 × 5 cm 2 , $$650~\upmu \text {m}$$ 650 μ m thick silicon substrate coupled to a single kinetic inductance detector made of a three-layer aluminum-titanium-aluminum. The baseline energy resolution is $$34\pm 1$$ 34 ± 1 (stat) $$\pm 2$$ ± 2 (syst) eV RMS and the response time is $$120~\upmu $$ 120 μ s. These features, along with the natural multiplexing capability of kinetic inductance detectors, meet the requirements of future large-scale experiments.

Background radiation has been identified as a key factor limiting the coherence times of superconducting circuits. Here, the authors measure the impact of environmental and cosmic radiation on a superconducting resonator with varying degrees of shielding, including an underground facility.

Abstract Molybdenum based crystals such as $$\hbox {Li}_{2}\hbox {MoO}_{4}$$ Li2MoO4 and CaMoO$$_4$$ 4 are emerging as leading candidates for next generation experiments searching for neutrino-less double beta decay with cryogenic calorimeters (CUPID, AMoRE). The exquisite energy resolution and high radio-purity of these crystals come at the cost of a potentially detrimental background source: the two neutrinos double beta decay of $$^{100}$$ 100 Mo. Indeed, the fast half-life of this decay mode, combined with the slow response of cryogenic calorimeters, would result in pile-up events in the energy region of interest for neutrino-less double beta decay, reducing the experimental sensitivity. This background can be suppressed using fast and high sensitivity cryogenic light detectors, provided that the scintillation time constant itself does not limit the time resolution. We developed a new detection technique exploiting the high sensitivity, the fast time response and the multiplexing capability of Kinetic Inductance Detectors. We applied the proposed technique to a $$2\times 2\times 2$$ 2×2×2 cm$$^3$$ 3 $$\hbox {Li}_{2}\hbox {MoO}_{4}$$ Li2MoO4 crystal, which was chosen as baseline option for CUPID. We measured simultaneously both the phonon and scintillation signals with KIDs. We derived the scintillation time constant of this compound at millikelvin temperatures obtaining $$\tau _{scint} = 84.5\pm 4.5\mathrm {(syst)}\pm 1.0\mathrm {(stat)}$$ τscint=84.5±4.5(syst)±1.0(stat) $$\mu $$ μ s, constant between 10 and 190 mK.

We report a strain-induced direct-to-indirect band gap transition in mechanically deformed WS_{2} monolayers (MLs). The necessary amount of strain is attained by proton irradiation of bulk WS_{2} and the ensuing formation of 1-ML-thick, H_{2}-filled domes. The electronic properties of the curved MLs are mapped by spatially and time-resolved microphotoluminescence, revealing the mechanical stress conditions that trigger the variation of the band gap character. This general phenomenon, also observed in MoS_{2} and WSe_{2}, further increases our understanding of the electronic structure of transition metal dichalcogenide MLs and holds a great relevance for their optoelectronic applications.

The electronic properties of In(AsN) before and after post-growth sample irradiation with increasing doses of atomic hydrogen have been investigated by photoluminescence. The electron density increases in In(AsN) but not in N-free InAs, until a Fermi stabilization energy is established. A hydrogen ϵ+/− transition level just below the conduction band minimum accounts for the dependence of donor formation on N, in agreement with a recent theoretical report highlighting the peculiarity of InAs among III–V compounds. Raman scattering measurements indicate the formation of N–H complexes that are stable under thermal annealing up to ∼500 K. Finally, hydrogen does not passivate the electronic activity of N, thus leaving the band gap energy of In(AsN) unchanged, once more in stark contrast to what has been reported in other dilute nitride alloys. [ABSTRACT FROM AUTHOR]

The effects of external perturbations—such as temperature, photo-excited carrier density, and magnetic field—on the electronic properties of Ga(AsBi) alloys are investigated in a large range of Bi-concentration (x up to ∼11%). These studies allow us to disclose the existence of Bi-induced localized states that largely contribute to the recombination spectra up to relatively-high temperature (T ∼ 150 K). The sensitivity of the band-gap energy to temperature variation is found to diminish strongly with Bi-concentration and to result in a reduction of about a factor of two at the highest concentrations. Magneto-photoluminescence studies have also revealed the role exerted by the Bi-induced levels on the host band states and have disclosed an unexpectedly strong carrier–carrier scattering, which hampers the observation of Landau-level quantization at low magnetic fields. An unusual compositional dependence of the exciton reduced mass, as well as an unexpected increase of the electron effective mass at relatively-low Bi-concentration (x < 6%), are reported and related to the presence of Bi-induced states. [ABSTRACT FROM AUTHOR]