Photonic heat transport in three terminal superconducting circuit

| openaire: EC/H2020/742559/EU//SQH | openaire: EC/H2020/843706/EU//XmonMASER Funding Information: We acknowledge valuable discussions with J. Ankerhold and G. Kurizki. This work was supported by the Academy of Finland Centre of Excellence program (project 312057), by the European Union’s Horizon 2020 research and innovation programme under the European Research Council (ERC) programme (grant agreement 742559), and Marie Sklodowska-Curie grant agreement No 843706. We acknowledge the provision of facilities and technical support of the Low Temperature Laboratory at Aalto University and the Otaniemi research infrastructure for Micro and Nanotechnologies (OtaNano). We also thank VTT Technical Research Center for depositing the Nb used in this work.We report an experimental realization of a three-terminal photonic heat transport device based on a superconducting quantum circuit. The central element of the device is a flux qubit made of a superconducting loop containing three Josephson junctions, which can be tuned by magnetic flux. It is connected to three resonators terminated by resistors. By heating one of the resistors and monitoring the temperatures of the other two, we determine photonic heat currents in the system and demonstrate their tunability by magnetic field at the level of 1 aW. We determine system parameters by performing microwave transmission measurements on a separate nominally identical sample and, in this way, demonstrate clear correlation between the level splitting of the qubit and the heat currents flowing through it. Our experiment is an important step towards realization of heat transistors, heat amplifiers, masers pumped by heat and other quantum heat transport devices.Peer reviewe

Physical Vapor Deposition Features of Ultrathin Nanocrystals of Bi2(TexSe1- x)3

Structural and electronic properties of ultrathin nanocrystals of chalcogenide Bi2(TexSe1-x)3were studied. The nanocrystals were formed from the parent compound Bi2Te2Se on as-grown and thermally oxidized Si(100) substrates using Ar-assisted physical vapor deposition, resulting in well-faceted single crystals several quintuple layers thick and a few hundreds nanometers large. The chemical composition and structure of the nanocrystals were analyzed by energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, electron backscattering, and X-ray diffraction. The electron transport through nanocrystals connected to superconducting Nb electrodes demonstrated Josephson behavior, with the predominance of the topological channels [ Stolyarov et al. Commun. Mater., 2020, 1, 38 ]. The present paper focuses on the effect of the growth conditions on the morphology, structural, and electronic properties of nanocrystals

Fluorescence and Cytotoxicity of Cadmium Sulfide Quantum Dots Stabilized on Clay Nanotubes

Quantum dots (QD) are widely used for cellular labeling due to enhanced brightness, resistance to photobleaching, and multicolor light emissions. CdS and CdxZn1−xS nanoparticles with sizes of 6–8 nm were synthesized via a ligand assisted technique inside and outside of 50 nm diameter halloysite clay nanotubes (QD were immobilized on the tube’s surface). The halloysite–QD composites were tested by labeling human skin fibroblasts and prostate cancer cells. In human cell cultures, halloysite–QD systems were internalized by living cells, and demonstrated intense and stable fluorescence combined with pronounced nanotube light scattering. The best signal stability was observed for QD that were synthesized externally on the amino-grafted halloysite. The best cell viability was observed for CdxZn1−xS QD immobilized onto the azine-grafted halloysite. The possibility to use QD clay nanotube core-shell nanoarchitectures for the intracellular labeling was demonstrated. A pronounced scattering and fluorescence by halloysite–QD systems allows for their promising usage as markers for biomedical applications

Josephson current mediated by ballistic topological states in Bi2Te2.3Se0.7 single nanocrystals

Topological insulators in contact with a superconductor could house unusual physical states such as Majorana fermions. Here, the authors fabricate and report the  electron-transport characteristics of Josephson junctions built using a nanoscale topological insulator, finding evidence for ballistic transport in the surface states of the nanocrystals

Rarely naturalized, but widespread and even invasive: the paradox of a popular pet terrapin expansion in Eurasia

The North American terrapin, the red-eared slider, has globally recognized invasive status. We built a new extensive database using our own original and literature data on the ecology of this reptile, representing information on 1477 water bodies throughout Eurasia over the last 50 years. The analysis reveals regions of earliest introductions and long-term spatio-temporal dynamics of the expansion covering now 68 Eurasian countries, including eight countries reported here for the first time. We established also long-term trends in terms of numbers of terrapins per aquatic site, habitat occupation, and reproduction success. Our investigation has revealed differences in the ecology of the red-eared slider in different parts of Eurasia. The most prominent expression of diverse signs of invasion success (higher portion of inhabited natural water bodies, higher number of individuals per water body, successful overwintering, occurrence of juvenile individuals, successful reproduction, and establishment of populations) are typical for Europe, West Asia and East Asia and tend to be restricted to coastal regions and islands. Reproduction records coincide well with the predicted potential range based on climatic requirements but records of successful wintering have a wider distribution. This invader provides an excellent and possibly unique (among animals) example of wide alien distribution, without the establishment of reproducing populations, but through the recruitment of new individuals to rising pseudopopulations due to additional releases. Therefore, alongside the potential reproduction range, a cost-effective strategy for population control must take in account the geographical area of successful wintering. Graphical abstrac