An experimental realization of a ballistic superconductor proximitized semiconductor nanowire device is a necessary step towards engineering topological quantum electronics. Here, we report on ballistic transport in I...An experimental realization of a ballistic superconductor proximitized semiconductor nanowire device is a necessary step towards engineering topological quantum electronics. Here, we report on ballistic transport in In Sb nanowires grown by molecular-beam epitaxy contacted by superconductor electrodes. At an elevated temperature, clear conductance plateaus are observed at zero magnetic field and in agreement with calculations based on the Landauer formula. At lower temperature, we have observed characteristic Fabry–Pérot patterns which confirm the ballistic nature of charge transport.Furthermore, the magnetoconductance measurements in the ballistic regime reveal a periodic variation related to the Fabry–Pérot oscillations. The result can be reasonably explained by taking into account the impact of magnetic field on the phase of ballistic electron＇s wave function, which is further verified by our simulation. Our results pave the way for better understanding of the quantum interference effects on the transport properties of In Sb nanowires in the ballistic regime as well as developing of novel device for topological quantum computations.展开更多
This article provides a review of tropical cyclone(TC)surface wind estimation from an operational forecasting perspective.First,we provide a summary of operational forecast center practices and historical databases.Ne...This article provides a review of tropical cyclone(TC)surface wind estimation from an operational forecasting perspective.First,we provide a summary of operational forecast center practices and historical databases.Next,we discuss current and emerging objective estimates of TC surface winds,including algorithms,archive datasets,and individual algorithm strengths and weaknesses as applied to operational TC surface wind forecast parameters.Our review leads to recommendations about required surface coverage—an area covering at least 1100 km from center of TC at a 2-km resolution in the inner-core,and at a frequency of at least once every 6 h.This is enough coverage to support a complete analysis of the TC surface wind field from center to the extent of the 34-kt(17 m s^(-1))winds at 6-h intervals.We also suggest future designs of TC surface wind capabilities include funding to ensure near real-time data delivery to operators so that operational evaluation and use are feasible within proposed budgets.Finally,we suggest that users of archived operational wind radii datasets contact operational organizations to ensure these datasets are appropriate for their needs as the datasets vary in quality through time and space,even from a single organisation.展开更多
Ternary III-V nanowires （NWs） cover a wide range of wavelengths in the solar spectrum and would greatly benefit from being synthesized as position-controlled arrays for improved vertical yield, reproducibility, and ...Ternary III-V nanowires （NWs） cover a wide range of wavelengths in the solar spectrum and would greatly benefit from being synthesized as position-controlled arrays for improved vertical yield, reproducibility, and tunable optical absorption. Here, we report on successful selective-area epitaxy of metal-particle-free vertical InxGa1-xP NW arrays using metal-organic vapor phase epitaxy and detail their optical properties. A systematic growth study establishes the range of suitable growth parameters to obtain uniform NW growth over a large array. The optical properties of the NWs were characterized by room-temperature cathodoluminescence spectroscopy. Tunability of the emission wavelength from 870 nm to approximately 800 nm was achieved. Transmission electron microscopy and energy dispersive X-ray measurements performed on cross- section samples revealed a pure wurtzite crystal structure with very few stacking faults and a slight composition gradient along the NW growth axis.展开更多
We demonstrate a simple way of fabricating high performance tunnel devices from p-doped InAs nanowires by tailoring the n-doped surface accumulation layer inherent to InAs surfaces. By using appropriate ammonium sulfi...We demonstrate a simple way of fabricating high performance tunnel devices from p-doped InAs nanowires by tailoring the n-doped surface accumulation layer inherent to InAs surfaces. By using appropriate ammonium sulfide based surface passivation before metallization without any further thermal treatment, we demonstrate characteristics of tunnel p-n junctions, namely Esaki and backward diodes, with figures of merit better than previously published for InAs homojunctions. The further optimization of both the surface doping, in a quantitative way, and the device geometry allows us to demonstrate that these nanowire-based technologically-simple diodes have promising direct current characteristics for integrated high frequency detection or generation.展开更多
Nano Research volume We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs.Signatures of optical transitions between four valence bands and two co...Nano Research volume We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs.Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory.The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate.From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs.This information is vital to the development of crystal phase engineering of this important III-V semiconductor.展开更多
The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase...The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes.Here,we have fabricated and measured Al-InSb nanowire quantum dot-Al devices.In the Kondo regime,a supercurrent-induced zero-bias conductance peak emerges.This zero-bias peak shows an anomalous negative magnetoresistance(NMR)at weak magnetic fields.We attribute this anomalous NMR to quasiparticle trapping at vortices in the superconductor leads as a weak magnetic field is applied.The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current.This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.展开更多
In this paper,we summarizefindings from the Tenth International Workshop on Tropical Cyclones(IWTC-10)subgroup on forecasting wind hazards and impacts.We found that new approaches to TC wind hazard forecasts continue t...In this paper,we summarizefindings from the Tenth International Workshop on Tropical Cyclones(IWTC-10)subgroup on forecasting wind hazards and impacts.We found that new approaches to TC wind hazard forecasts continue to be developed and are becoming an increasingly common product offered by operational centres.To add greater context to wind risk information for users,many operational and research centres are also working to develop impact-based forecasts that incorporate hazard,vulnerability,and exposure data.Efforts to develop tropical cyclone wind impact forecasts present resourcing challenges,and when compared to wind hazard forecasting,are generally still in their infancy.Overall,both operational and research centres are extending significant efforts to meet the strong public need for accurate predictions of TC wind hazards and impacts around the world.展开更多
基金Project supported by the National Key Basic Research and Development Project of the Ministry of Science and Technology of China(Grant No.2016YFA0300601)the National Natural Science Foundation of China(Grant Nos.91221202,91421303,11374019,and 61321001)
文摘An experimental realization of a ballistic superconductor proximitized semiconductor nanowire device is a necessary step towards engineering topological quantum electronics. Here, we report on ballistic transport in In Sb nanowires grown by molecular-beam epitaxy contacted by superconductor electrodes. At an elevated temperature, clear conductance plateaus are observed at zero magnetic field and in agreement with calculations based on the Landauer formula. At lower temperature, we have observed characteristic Fabry–Pérot patterns which confirm the ballistic nature of charge transport.Furthermore, the magnetoconductance measurements in the ballistic regime reveal a periodic variation related to the Fabry–Pérot oscillations. The result can be reasonably explained by taking into account the impact of magnetic field on the phase of ballistic electron＇s wave function, which is further verified by our simulation. Our results pave the way for better understanding of the quantum interference effects on the transport properties of In Sb nanowires in the ballistic regime as well as developing of novel device for topological quantum computations.
基金provided funding C.Sampson through Program Element 0603207NCalifornia Institute of Technology under a contract with the NASA,Government sponsorship acknowledged+5 种基金funding by the NASA Team Science Utilization of the Soil Moisture Active-Passive Mission(SUSMAP,contract NNH17CA04C)the NASA Ocean Vector Wind Science Team(OVWST,contract 80HQTR19C0003)supported ESA through S1-4SCI Ocean Study project(Contract No.4000115170/15/I-SBo)Sentinel-1 A Mission Performance Center(Contract No.4000107360/12/I-LG)CHEFS EUMETSAT project and by public funds(Ministere de l’Education Nationale,de l’Enseignement Superieur et de la Recherche,FEDER,Region Bretagne,Conseil General du Finistere,Brest Metropole)support of ESA in the frame of the SMOS Wind Data Service contract(http://www.smosstorm.org/)
文摘This article provides a review of tropical cyclone(TC)surface wind estimation from an operational forecasting perspective.First,we provide a summary of operational forecast center practices and historical databases.Next,we discuss current and emerging objective estimates of TC surface winds,including algorithms,archive datasets,and individual algorithm strengths and weaknesses as applied to operational TC surface wind forecast parameters.Our review leads to recommendations about required surface coverage—an area covering at least 1100 km from center of TC at a 2-km resolution in the inner-core,and at a frequency of at least once every 6 h.This is enough coverage to support a complete analysis of the TC surface wind field from center to the extent of the 34-kt(17 m s^(-1))winds at 6-h intervals.We also suggest future designs of TC surface wind capabilities include funding to ensure near real-time data delivery to operators so that operational evaluation and use are feasible within proposed budgets.Finally,we suggest that users of archived operational wind radii datasets contact operational organizations to ensure these datasets are appropriate for their needs as the datasets vary in quality through time and space,even from a single organisation.
文摘Ternary III-V nanowires （NWs） cover a wide range of wavelengths in the solar spectrum and would greatly benefit from being synthesized as position-controlled arrays for improved vertical yield, reproducibility, and tunable optical absorption. Here, we report on successful selective-area epitaxy of metal-particle-free vertical InxGa1-xP NW arrays using metal-organic vapor phase epitaxy and detail their optical properties. A systematic growth study establishes the range of suitable growth parameters to obtain uniform NW growth over a large array. The optical properties of the NWs were characterized by room-temperature cathodoluminescence spectroscopy. Tunability of the emission wavelength from 870 nm to approximately 800 nm was achieved. Transmission electron microscopy and energy dispersive X-ray measurements performed on cross- section samples revealed a pure wurtzite crystal structure with very few stacking faults and a slight composition gradient along the NW growth axis.
文摘We demonstrate a simple way of fabricating high performance tunnel devices from p-doped InAs nanowires by tailoring the n-doped surface accumulation layer inherent to InAs surfaces. By using appropriate ammonium sulfide based surface passivation before metallization without any further thermal treatment, we demonstrate characteristics of tunnel p-n junctions, namely Esaki and backward diodes, with figures of merit better than previously published for InAs homojunctions. The further optimization of both the surface doping, in a quantitative way, and the device geometry allows us to demonstrate that these nanowire-based technologically-simple diodes have promising direct current characteristics for integrated high frequency detection or generation.
基金We acknowledge the financial support of the NSF through Grants DMR 1507844,DMR 1531373,and ECCS 1509706 and also the financial support of the Australian Research Council and the European Research Council(Grant No.716471,ACrossWire)The Australian National Fabrication Facility(ACT Node)is acknowledged for access to the growth facility used in this workThe Australian Microscopy and Microanalysis Research Facility is acknowledged for access to the electron microscopes used in this work.
文摘Nano Research volume We use polarized photocurrent spectroscopy in a nanowire device to investigate the band structure of hexagonal Wurtzite InAs.Signatures of optical transitions between four valence bands and two conduction bands are observed which are consistent with the symmetries expected from group theory.The ground state transition energy identified from photocurrent spectra is seen to be consistent with photoluminescence emitted from a cluster of nanowires from the same growth substrate.From the energies of the observed bands we determine the spin orbit and crystal field energies in Wurtzite InAs.This information is vital to the development of crystal phase engineering of this important III-V semiconductor.
基金supported by the Swedish Research Council(VR)the National Natural Science Foundation of China(Grant Nos.92165208,11874071,91221202,91421303,and 11904399)+7 种基金the National Key Research and Development Program of China(Grant Nos.2016YFA0300601,and 2017YFA0303304)Beijing Academy of Quantum Information Sciences(Grant No.Y18G22)the financial supports by Hunan Provincial Science Foundation for Distinguished Young Scholars(Grant No.2021JJ10043)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302401)the financial support by the Spanish Ministry of Economy and Competitiveness(Grant No.PID2020-117347GBI00)the financial supports by the Spanish Ministry of Economy and Competitiveness(Grant No.PID2020-11778GB-I00)the Mara de Maeztu project CEX2021-001164-M funded by the MCIN/AEI/10.13039/501100011033the supports from CSIC Research Platform PTI-001 and through the grant LINKB20072(CSIC)。
文摘The interplay between superconductivity and the Kondo effect has stimulated significant interest in condensed matter physics.They compete when their critical temperatures are close and can give rise to a quantum phase transition that can mimic Majorana zero modes.Here,we have fabricated and measured Al-InSb nanowire quantum dot-Al devices.In the Kondo regime,a supercurrent-induced zero-bias conductance peak emerges.This zero-bias peak shows an anomalous negative magnetoresistance(NMR)at weak magnetic fields.We attribute this anomalous NMR to quasiparticle trapping at vortices in the superconductor leads as a weak magnetic field is applied.The trapping effect lowers the quasiparticle-caused dissipation and thus enhances the Josephson current.This work connects the vortex physics and the supercurrent tunneling in Kondo regimes and can help further understand the physics of Josephson quantum dot system.
文摘In this paper,we summarizefindings from the Tenth International Workshop on Tropical Cyclones(IWTC-10)subgroup on forecasting wind hazards and impacts.We found that new approaches to TC wind hazard forecasts continue to be developed and are becoming an increasingly common product offered by operational centres.To add greater context to wind risk information for users,many operational and research centres are also working to develop impact-based forecasts that incorporate hazard,vulnerability,and exposure data.Efforts to develop tropical cyclone wind impact forecasts present resourcing challenges,and when compared to wind hazard forecasting,are generally still in their infancy.Overall,both operational and research centres are extending significant efforts to meet the strong public need for accurate predictions of TC wind hazards and impacts around the world.
