物理与天体物理最新文献

{"title":"Molecular beam epitaxy and band structures of type-II antiferromagnetic semiconductor EuTe thin films","authors":"Xiaodong Qiu, Zhixiong Xiao, Fan Yu, Yuling Yin, Lin Huang, Bin Yang, Qichao Tian, Kaili Wang, Yuyang Mu, Qinghao Meng, Xiangang Wan, Junming Liu, Di Wu, Yi Zhang","doi":"10.1063/5.0227254","DOIUrl":"https://doi.org/10.1063/5.0227254","url":null,"abstract":"The rare-earth Eu-based compounds with a unique half-filled 4f orbital have attracted an amount of research interest recently. Here, we synthesized EuTe(001) single-crystal thin films on SrTiO3(001) substrate via molecular beam epitaxy (MBE). The scanning tunneling microscopy and x-ray diffraction results indicate that the grown EuTe thin films orientated as EuTe[100]//SrTiO3[110] in plane. In the angle-resolved photoemission spectroscopic (ARPES) measurements, the grown EuTe films show a semiconductive band structure with the valence band maximum lying on the center point of the Brillouin zone. The bandgap size of EuTe was further identified by the optical transmission spectra as 2.2 eV. The antiferromagnetic transition temperature of the grown EuTe film is 10.5 K measured by a superconductive quantum interference device (SQUID). Our results provide important information on the fundamental electronic structures for the further research and applications of the Eu-based compounds.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142601226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Islands identified","authors":"Guosheng Xu, Youwen Sun","doi":"10.1038/s41567-024-02670-2","DOIUrl":"https://doi.org/10.1038/s41567-024-02670-2","url":null,"abstract":"Filamentary eruptions from the plasma edge in fusion devices pose a critical threat to their integrity. The identification of magnetic islands at the top of the edge explains how these eruptions are suppressed by resonant magnetic perturbations.","PeriodicalId":19100,"journal":{"name":"Nature Physics","volume":null,"pages":null},"PeriodicalIF":19.6,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142601272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Highly anisotropic superconducting gap near the nematic quantum critical point of FeSe1−xSx","authors":"Pranab Kumar Nag, Kirsty Scott, Vanuildo S. de Carvalho, Journey K. Byland, Xinze Yang, Morgan Walker, Aaron G. Greenberg, Peter Klavins, Eduardo Miranda, Adrian Gozar, Valentin Taufour, Rafael M. Fernandes, Eduardo H. da Silva Neto","doi":"10.1038/s41567-024-02683-x","DOIUrl":"https://doi.org/10.1038/s41567-024-02683-x","url":null,"abstract":"<p>Nematic phases, in which electrons in a solid spontaneously break rotational symmetry while preserving translational symmetry, exist in several families of unconventional superconductors. Superconductivity mediated by nematic fluctuations is well established theoretically, but it has yet to be unambiguously identified experimentally. One major challenge is that nematicity is often intertwined with other degrees of freedom, such as magnetism and charge order. The FeSe_1−<i>x</i>S_<i>x</i> family of superconductors provides an opportunity to explore this concept, as it features an isolated nematic phase that can be suppressed by sulfur substitution at a quantum critical point where the nematic fluctuations are the largest. Here we determine the momentum structure of the superconducting gap near the centre of the Brillouin zone in FeSe_0.81S_0.19—close to the quantum critical point—and find that it is anisotropic and nearly nodal. The gap minima occur in a direction that is rotated 45° with respect to the Fe–Fe direction, unlike the usual isotropic gaps due to spin-mediated pairing in other tetragonal Fe-based superconductors. Instead, we find that the gap structure agrees with theoretical predictions for superconductivity mediated by nematic fluctuations, indicating a change in the pairing mechanism across the phase diagram of FeSe_1−<i>x</i>S_<i>x</i>.</p>","PeriodicalId":19100,"journal":{"name":"Nature Physics","volume":null,"pages":null},"PeriodicalIF":19.6,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142601273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A privacy-preserving quantum authentication for vehicular communication","authors":"Koushik Challagundla,&nbsp;Kartick Sutradhar","doi":"10.1007/s11128-024-04582-9","DOIUrl":"10.1007/s11128-024-04582-9","url":null,"abstract":"<div><p>Vehicular ad hoc networks (VANETs) involve the interconnection of numerous vehicles, enabling them to communicate vital information through a network designed for efficient vehicle-to-vehicle communication. This dynamic connectivity in VANETs allows for spontaneous communication among random vehicles, fostering real-time exchange of critical data such as traffic conditions, road hazards, and other relevant information. This cooperative network improves road safety and traffic efficiency by allowing vehicles to exchange information and respond to the ever-changing conditions in their proximity, leading to an overall enhancement in the transportation system. In this paper, we propose an authentication protocol that remains unconditionally secure against quantum attacks. This paper explores the integration of quantum authentication with blockchain technology to establish a secure framework for VANETs. We introduce a quantum blockchain framework aimed at augmenting the security of VANETs. The paper presents a comprehensive analysis of the quantum blockchain’s potential to mitigate common security threats in VANETs, including data tampering, eavesdropping, and unauthorized access.\u0000</p></div>","PeriodicalId":746,"journal":{"name":"Quantum Information Processing","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"BASS","authors":"Kriti K. Gupta, Claudio Ricci, Matthew J. Temple, Alessia Tortosa, Michael J. Koss, Roberto J. Assef, Franz E. Bauer, Richard Mushotzy, Federica Ricci, Yoshihiro Ueda, Alejandra F. Rojas, Benny Trakhtenbrot, Chin-Shin Chang, Kyuseok Oh, Ruancun Li, Taiki Kawamuro, Yaherlyn Diaz, Meredith C. Powell, Daniel Stern, C. Megan Urry, Fiona Harrison, Brad Cenko","doi":"10.1051/0004-6361/202450567","DOIUrl":"https://doi.org/10.1051/0004-6361/202450567","url":null,"abstract":"We present one of the largest multiwavelength studies of simultaneous optical-to-X-ray spectral energy distributions (SEDs) of unobscured (<i>N<i/><sub>H<sub/> < 10<sup>22<sup/> cm<sup>−2<sup/>) active galactic nuclei (AGN) in the local Universe. Using a representative sample of hard-X-ray-selected AGN from the 70-month <i>Swift<i/>/BAT catalog, with optical/UV photometric data from <i>Swift<i/>/UVOT and X-ray spectral data from <i>Swift<i/>/XRT, we constructed broadband SEDs of 236 nearby AGN (0.001 < <i>z<i/> < 0.3). We employed GALFIT to estimate host galaxy contamination in the optical/UV and determine the intrinsic AGN fluxes. We used an absorbed power law with a reflection component to model the X-ray spectra and a dust-reddened multi-temperature blackbody to fit the optical/UV SED. We calculated intrinsic luminosities at multiple wavelengths, total bolometric luminosities (<i>L<i/><sub>bol<sub/>), optical-to-X-ray spectral indices (<i>α<i/><sub>ox<sub/>), and multiple bolometric corrections (<i>κ<i/><sub><i>λ<i/><sub/>) in the optical, UV, and X-rays. We used black hole masses obtained by reverberation mapping and the virial method to estimate Eddington ratios (<i>λ<i/><sub>Edd<sub/>) for all our AGN. We confirm the tight correlation (scatter = 0.45 dex) between UV (2500 Å) and X-ray (2 keV) luminosity for our sample. We observe a significant decrease in <i>α<i/><sub>ox<sub/> with <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>, suggesting that brighter sources emit more UV photons per X-rays. We report a second-order regression relation (scatter = 0.15 dex) between the 2–10 keV bolometric correction (<i>κ<i/><sub>2 − 10<sub/>) and <i>α<i/><sub>ox<sub/>, which is useful to compute <i>L<i/><sub>bol<sub/> in the absence of multiband SEDs. We also investigate the dependence of optical/UV bolometric corrections on the physical properties of AGN and obtain a significant increase in the UV bolometric corrections (<i>κ<i/><sub>W2<sub/> and <i>κ<i/><sub>M2<sub/>) with <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>, unlike those in the optical (<i>κ<i/><sub>V<sub/> and <i>κ<i/><sub>B<sub/>), which are constant across five orders of <i>L<i/><sub>bol<sub/> and <i>λ<i/><sub>Edd<sub/>. We obtain significant dispersions (∼0.1–1 dex) in all bolometric corrections, and hence recommend using appropriate relations with observed quantities while including the reported scatter, instead of their median values.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610421","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contemporaneous high-angular-resolution imaging of the AGB star W Hya in vibrationally excited H2O lines and visible polarized light with ALMA and VLT/SPHERE-ZIMPOL","authors":"K. Ohnaka, K. T. Wong, G. Weigelt, K.-H. Hofmann","doi":"10.1051/0004-6361/202451977","DOIUrl":"https://doi.org/10.1051/0004-6361/202451977","url":null,"abstract":"<i>Aims.<i/> We present contemporaneous high-angular-resolution millimeter imaging and visible polarimetric imaging of the nearby asymptotic giant branch (AGB) star W Hya to better understand the dynamics and dust formation within a few stellar radii.<i>Methods.<i/> The star W Hya was observed in two vibrationally excited H<sub>2<sub/>O lines at 268 and 251 GHz with Atacama Large Millimeter/submillimeter Array (ALMA) at a spatial resolution of 16 × 20 mas and at 748 and 820 nm at a resolution of 26 × 27 mas with the Very Large Telescope (VLT)/Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE)-Zurich Imaging Polarimeter (ZIMPOL).<i>Results.<i/> ALMA’s high spatial resolution allowed us to image strong emission of the vibrationally excited H<sub>2<sub/>O line at 268 GHz (<i>v<i/><sub>2<sub/> = 2, <i>J<i/><sub><i>K<i/><sub><i>a<i/><sub/>, <i>K<i/><sub><i>c<i/><sub/><sub/> = 6<sub>5, 2<sub/>–7<sub>4, 3<sub/>) over the stellar surface instead of absorption against the continuum, which is expected for thermal excitation. Strong, spotty emission was also detected along and just outside the stellar disk limb at an angular distance of ∼40 mas (∼1.9 <i>R<i/><sub>⋆<sub/>), extending to ∼60 mas (∼2.9 <i>R<i/><sub>⋆<sub/>). Another H<sub>2<sub/>O line (<i>v<i/><sub>2<sub/> = 2, <i>J<i/><sub><i>K<i/><sub><i>a<i/><sub/>, <i>K<i/><sub><i>c<i/><sub/><sub/> = 9<sub>2, 8<sub/>–8<sub>3, 5<sub/>) at 251 GHz with a similar upper-level energy was tentatively identified, which shows absorption over the stellar surface. This suggests that the emission over the surface seen in the 268 GHz H<sub>2<sub/>O line is suprathermal or even maser emission. The estimated gas temperature and H<sub>2<sub/>O density are consistent with the radiatively pumped masers. The 268 GHz H<sub>2<sub/>O line reveals global infall at up to ∼15 km s<sup>−1<sup/> within 2–3 <i>R<i/><sub>⋆<sub/>, but outflows at up to ∼8 km s<sup>−1<sup/> are also present. The polarized intensity maps obtained in the visible reveal clumpy dust clouds forming within ∼40 mas (∼1.9 <i>R<i/><sub>⋆<sub/>) with a particularly prominent cloud in the SW quadrant and a weaker cloud in the east. The 268 GHz H<sub>2<sub/>O emission overlaps very well with the visible polarized intensity maps, which suggests that both the nonthermal and likely maser H<sub>2<sub/>O emission and the dust originate from dense, cool pockets in the inhomogeneous atmosphere within ∼2–3 <i>R<i/><sub>⋆<sub/>.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":null,"pages":null},"PeriodicalIF":6.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142610564","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nitrogen-doped Ga2O3 current blocking layer using MOCVD homoepitaxy for high-voltage and low-leakage Ga2O3 vertical device fabrication","authors":"Xiaorui Xu, Desen Chen, Yaoping Lu, Titao Li, Xueli Han, Duanyang Chen, Hongji Qi, Dan Yang, Minmin Zhu, Haizhong Zhang, Xiaoqiang Lu","doi":"10.1063/5.0239622","DOIUrl":"https://doi.org/10.1063/5.0239622","url":null,"abstract":"In this Letter, a high-quality and high-resistivity nitrogen (N)-doped Ga2O3 current blocking layer (CBL) is grown utilizing metal-organic chemical vapor deposition homoepitaxial technology. By using nitrous oxide (N2O) as oxygen source for Ga2O3 growth and N source for doping and controlling the growth temperature, the grown CBL can effectively achieve high (∼1019 cm−3) or low (∼1017 cm−3) N doping concentrations, as well as high crystal quality. Furthermore, the electrical properties of the developed CBL are verified at the device level, which shows that the device using the CBL can withstand bidirectional voltages exceeding 3.5 kV with very low leakage (≤1 × 10−4 A/cm2). This work can pave the way for the realization of high-voltage and low-leakage Ga2O3 vertical devices, especially metal-oxide-semiconductor field effect transistors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142609895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A perspective on structured light's applications","authors":"Carmelo Rosales-Guzmán, Valeria Rodríguez-Fajardo","doi":"10.1063/5.0236477","DOIUrl":"https://doi.org/10.1063/5.0236477","url":null,"abstract":"For the past few decades, structured light has been gaining popularity across various research fields. Its fascinating properties have been exploited for both previously unforeseen and established applications from new perspectives. Crucial to this is the several techniques that have been proposed for both their generation and characterization. On the one hand, the former has been boosted by the invention of computer-controlled devices, which combined with a few optical components allow flexible and complete control of the spatial and polarization degrees of freedom on light, thus enabling a plethora of proof-of-principle experiments for novel and old applications. On the other hand, characterizing light beams is important not only for gaining better insights into light's properties but also for potentially being used as metrics. In this perspective, we thus offer our take on a few key applied research fields where structured light is particularly promising, as well as some pivotal generation and characterization techniques. In addition, we share our vision of where we believe structured light's applications are moving toward.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142609942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of low sodium type II silicon clathrate film spin dynamics","authors":"Joseph P. Briggs, Yinan Liu, P. Craig Taylor, Meenakshi Singh, Reuben T. Collins, Carolyn A. Koh","doi":"10.1063/5.0230407","DOIUrl":"https://doi.org/10.1063/5.0230407","url":null,"abstract":"Type II Si clathrate is a Si-based, crystalline alternative to diamond silicon with interesting optoelectronic properties. Here, a pulsed electron paramagnetic resonance study of the spin dynamics of sodium-doped, type II NaxSi136 silicon clathrate films is reported. Focusing on the hyperfine lines of isolated Na atoms, the temperature dependence of the electron spin dynamics is examined from 6 to 25 K. The measurements exhibit multi-exponential decay, indicating multiple spin relaxation rates in the system. As expected, spin relaxation time (T1) increases rapidly with decreasing temperature, reaching ∼300 μs at 6.4 K. The phase memory (TM) shows less temperature dependence with a value of ∼3 μs at the same temperature. The temperature dependence of T1 exhibits Arrhenius behavior in the measurement range consistent with an Orbach pathway. There are strong similarities to the spin behavior of other defect donors in diamond silicon. The results provide insights into the potential of Si clathrates for spin-based applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":null,"pages":null},"PeriodicalIF":4.0,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142609956","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anomalous Floquet Phases. A resonance phenomena","authors":"Álvaro Gómez-León","doi":"10.22331/q-2024-11-13-1522","DOIUrl":"https://doi.org/10.22331/q-2024-11-13-1522","url":null,"abstract":"Floquet topological phases emerge when systems are periodically driven out-of-equilibrium. They gained attention due to their external control, which allows to simulate a wide variety of static systems by just tuning the external field in the high frequency regime. However, it was soon clear that their relevance goes beyond that, as for lower frequencies, anomalous phases without a static counterpart are present and the bulk-to-boundary correspondence can fail. In this work we discuss the important role of resonances in Floquet phases. For that, we present a method to find analytical solutions when the frequency of the drive matches the band gap, extending the well-known high frequency analysis of Floquet systems. With this formalism, we show that the topology of Floquet phases with resonances can be accurately captured in analytical terms. We also find a bulk-to-boundary correspondence between the number of edge states in finite systems and a set of topological invariants in different frames of reference, which crucially do not explicitly involve the micromotion. To illustrate our results, we periodically drive a SSH chain and a $pi$-flux lattice, showing that our findings remain valid in various two-band systems and in different dimensions. In addition, we notice that the competition between rotating and counter-rotating terms must be carefully treated when the undriven system is a semi-metal. To conclude, we discuss the implications to experimental setups, including the direct detection of anomalous topological phases and the measurement of their invariants.","PeriodicalId":20807,"journal":{"name":"Quantum","volume":null,"pages":null},"PeriodicalIF":6.4,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142600968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}