Since the original invention by Samuel P. Langley in 1878 5 , bolometers have gone a long way of improving the sensitivity and expanding the frequency range, from X-rays and optical/UV radiation to the submillimeter waves. The latter range contains approximately half the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang 6 .Because the performance of ground-based THz telescopes is severely limited by a strong absorption of THz radiation in the Earth atmosphere, the development of space-based THz telescopes will be crucial for better understanding of the Universe evolution. Active cooling of primary mirrors on these telescopes will reduce the mirror emission below the cosmic background level (Fig. 1) and greatly expand the range of observable faint objects. The development of advanced detectors with background-limited sensitivity for such telescopes poses a significant challenge. Indeed, the photon flux N ph , which corresponds to the cosmic background fluctuations, is very weak: at ν > 1 THz, the photon flux in a diffraction-limited beam does not exceed 100 photons/s for typical extragalactic emission lines with ν/δν ~ 1000. The noise equivalent power (NEP) of a background-limited detector should be less than NEP ph = hν 2N ph ~ 10 -20 W/Hz 1/2 , which is a factor of 100 lower than that of state-of-the-art bolometers.Although new detector concepts are coming into play nowadays 7,8 , bolometers still have a great potential for achieving the most challenging goals. Realization of the ultra-high sensitivity requires an unprecedented thermal isolation of a bolometer. Indeed, in the fluxintegrating regime (the bolometric time constant τ >> N ph -1 ), the minimum NEP is determined by the thermal energy fluctuations in a bolometer, and the corresponding value ofG is controlled by the thermal conductance G between the bolometer and its environment. In a traditional (the so-called "geometrically isolated") bolometer, G is determined by the number of relevant phonon and photon "channels" (modes) participating in thermal transport between the sensor and its environment. It has been shown recently for both photons 3,9 and phonons 10 that the thermal conductance of a short single channel is determined by the universal value G Q = π Despite a relatively small size of this micromachined device, the heat capacity C was still rather large, which resulted in a slow bolometric response with the time constant τ = C/G =1-10 s.Here we present a novel approach that enables a significant increase of the bolometer sensitivity and, at the same time, reduction of its response time. Fast response in a well isolated bolometer requires a very small heat capacity C and, thus, the nanoscale dimensions of a sensor.To overcome the limitation of fast phonon exchange, we realized the hot-electron regime 11, , 12 13 in superconducting nanobolometers at sub-Kelvin temperatures. In this case, a weak electronphonon coupling, which governs the effective thermal conductance, dramatically improves the thermal isola...

Three-dimensional (3D) Dirac semimetals, which possess 3D linear dispersion in the electronic structure as a bulk analogue of graphene, have lately generated widespread interest in both materials science and condensed matter physics. Recently, crystalline Cd3As2 has been proposed and proved to be a 3D Dirac semimetal that can survive in the atmosphere. Here, by using point contact spectroscopy measurements, we observe exotic superconductivity around the point contact region on the surface of Cd3As2 crystals. The zero-bias conductance peak (ZBCP) and double conductance peaks (DCPs) symmetric around zero bias suggest p-wave-like unconventional superconductivity. Considering the topological properties of 3D Dirac semimetals, our findings may indicate that Cd3As2 crystals under certain conditions could be topological superconductors, which are predicted to support Majorana zero modes or gapless Majorana edge/surface modes in the boundary depending on the dimensionality of the material.

Non-local entanglement is a key ingredient to quantum information processing. For photons, entanglement has been demonstrated 1 , but it is more difficult to observe for electrons. One approach is to use a superconductor, where electrons form spin-entangled Cooper pairs, which is a natural source for entangled electrons. For a three-terminal device consisting of a superconductor sandwiched between two normal metals, it has been predicted that Cooper pairs can split into spinentangled electrons flowing in the two spatially separated normal metals 2-5 , resulting in a negative non-local resistance and a positive current-current correlation 6,7 . The former prosperity has been observed 8,9 , but not the latter. Here we show that both characteristics can be observed, consistent with Cooper-pair splitting. Moreover, the splitting efficiency can be tuned by independently controlling the energy of the electrons passing the two superconductor/normal-metal interfaces, which may lead to better understanding and control of non-local entanglement.Entanglement of electrons may arise in the spatial degree of freedom (orbital entanglement) or the spin degree of freedom (spin entanglement). Recently, orbital entanglement in a fermionic Hanbury Brown and Twiss two-particle interferometer was observed using current cross-correlation measurements 10,11 , but further investigation is still required to verify the entangled states 12 . Spin-entanglement has been predicted to exist at the superconductor/normal-metal (SN) interface 2,3 and can be understood in the context of Andreev reflection 13 , in which a low-energy electron in the normal metal impinges on the SN interface and a hole is retroreflected whereas a Cooper pair is created in the superconductor.When two normal metals are coupled to a superconductor with spatial separation comparable to the superconducting coherence length (ξ S ), roughly the size of a Cooper pair, it is predicted that electrons in the two normal metals can also be coupled by means of a non-local analogue of Andreev reflection called crossed Andreev reflection 6,7 (CAR). As a Cooper pair splits into two coupled electrons with opposite spin orientation that are then injected into the two normal-metal leads, instantaneous currents of the same sign are generated across the two SN interfaces, giving rise to a negative non-local resistance as well as a positive current-current correlation between the SN junctions. Previous experimental attempts focused on non-local resistance measurements 8,9,14,15 , but the observation of CAR is complicated by another non-local process called elastic cotunnelling, in which electrons in the normal-metal leads tunnel across the superconductor with the help of Cooper pairs, resulting in a positive non-local resistance and a negative current-current

IntroductionProgressive fibrosis in systemic sclerosis (SSc) is linked to aberrant transforming growth factor beta (TGF-beta) signaling. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) blocks fibrogenic TGF-beta responses in vitro and in vivo. Reduced expression and function of PPAR-gamma in patients with SSc may contribute to progression of fibrosis. Here we evaluated the levels of adiponectin, a sensitive and specific index of PPAR-gamma activity, as a potential fibrogenic biomarker in SSc.MethodsAdiponectin levels were determined in the sera of 129 patients with SSc and 86 healthy controls, and serial determinations were performed in 27 patients. Levels of adiponectin mRNA in skin biopsies from SSc patients were assessed in an expression profiling microarray dataset. Regulation of adiponectin gene expression in explanted human subcutaneous preadipocytes and fibroblasts was examined by real-time quantitative PCR.ResultsPatients with diffuse cutaneous SSc had reduced serum adiponectin levels. A significant inverse correlation between adiponectin levels and the modified Rodnan skin score was observed. In longitudinal studies changes in serum adiponectin levels were inversely correlated with changes in skin fibrosis. Skin biopsies from a subset of SSc patients showed reduced adiponectin mRNA expression which was inversely correlated with the skin score. An agonist ligand of PPAR-gamma potently induced adiponectin expression in explanted mesenchymal cells in vitro.ConclusionsLevels of adiponectin, reflecting PPAR-gamma activity, are correlated with skin fibrosis and might have potential utility as a biomarker in SSc.

Two electrons bound in a singlet state have long provided a conceptual and pedagogical framework for understanding the non-local nature of entangled quantum objects. As bound singlet electrons separated by a coherence length of up to several hundred nanometres occur naturally in conventional BardeenCooper-Schrieffer superconductors in the form of Cooper pairs, recent theoretical investigations [1][2][3][4][5][6][7][8][9] have focused on whether electrons in spatially separated normal-metal probes placed within a coherence length of each other on a superconductor can be quantum mechanically coupled by the singlet pairs. This coupling is predicted to occur through the non-local processes of elastic cotunnelling and crossed Andreev reflection. In crossed Andreev reflection, the constituent electrons of a Cooper pair are sent into different normal probes while retaining their mutual coherence. In elastic cotunnelling, a sub-gap electron approaching the superconductor from one normal probe undergoes coherent, long-range tunnelling to the second probe that is mediated by the Cooper pairs in the condensate. Here, we present experimental evidence for coherent, non-local coupling between electrons in two normal metals linked by a superconductor. The coupling is observed in non-local resistance oscillations that are periodic in an externally applied magnetic flux.Three key predicted signatures of the elastic cotunnelling and crossed Andreev reflection (CAR) processes, shown schematically in Fig. 1, are (1) the coupling created between the normal probes is non-local-no current need be sent between them, (2) the resultant non-local signals decay rapidly as the probe separation is increased, exponentially over a superconducting coherence length ξ S or faster 4,5,7 and (3) the processes create quantum phase coherence between the two probes. Previous experiments looking for evidence of elastic cotunnelling and CAR have used normal-superconductor-normal and ferromagnetsuperconductor-ferromagnet devices. A current is sent across one normal-superconductor or ferromagnet-superconductor interface and non-local voltages are measured on the other normal or ferromagnet probe located less than a coherence length from the interface [10][11][12] . Although the measured non-local signals exhibit behaviour consistent with predictions (1) and (2), the coherent nature of the non-local signals has not been demonstrated. To establish the presence of non-local coherence, we have attached a hybrid normal-superconducting loop known as an Andreev interferometer [13][14][15] to one of the normal probes in a normal-superconductor-normal device. Modifying the phase of the electrons in the normal part of the Andreev interferometer by threading a magnetic flux through the loop leads to oscillations in the resistance of the loop with a period equal to the superconducting flux quantum Φ 0 = h/2e. Periodic oscillations can also be seen in the non-local resistance measured using normal probes placed off the interferometer, but coupled to it by a supercondu...

The search for nontrivial superconductivity in novel quantum materials is currently a most attractive topic in condensed matter physics and material science. The experimental studies have progressed quickly over the past couple of years. In this article, we report systematic studies of superconductivity in Au2Pb single crystals. The bulk superconductivity (onset transition temperature, Tconset= 1.3 K) of Au2Pb is characterized by both transport and diamagnetic measurements, where the upper critical field Hc2 shows unusual quasi-linear temperature dependence. The superconducting gap is revealed by point contact measurement with gold tip. However, when using tungsten (W) tip, which is much harder, the superconducting gap probed is largely enhanced as demonstrated by the increases of both Tconset and upper critical field (Hc2). This can be interpreted as a result of increase in density of states under external anisotropic stress imposed by the tip, as revealed by first-principles calculations. Furthermore, novel phase winding of the pseudospin texture along k-space loops around the Fermi energy is uncovered from the calculations, indicating that the observed superconductivity in Au2Pb may have nontrivial topology

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A 1T-TaS2 CDW system offers ultrabroadband and high photosensitivity from visible to terahertz wavelengths at room temperature.