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Hot-Electron Effects in InAs Nanowire Josephson Junctions

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Nano Research 2011年第3期4卷 259-265页

作者： stefano roddaro Andrea Pescaglini Daniele Ercolani Lucia Sorba Francesco Giazotto Fabio Beltram NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore P. za S. Silvestro 12 1-56127 Pisa Italy IIT@NEST Center for Nanotechnology Innovation P. za S. Silvestro 12 1-56127 Pisa Italy

The controlled tailoring of the energy distribution in an electron system opens the way to interesting new physics and device concepts, as demonstrated by research on metallic nanodevices during recent years. Here we investigate how Josephson coupling in a superconductor-InAs nanowire junction can be tuned by means of hot-electron injection and we show that a complete suppression of superconductive effects can be achieved using a power as low as 100 pW. Nanowires offer a novel design freedom as they allow axial and radial heterostructures to be defined as well as control over doping profiles, which can be crucial in the development of devices--such as nanorefrigerators--where precisely controlled and predictable energy barriers are mandatory. Our work provides estimates for unknown key thermal and electrical parameters, such as the electron-phonon coupling, in our InAs nanostructures.

关键词： Nanowire hot-electron Josephson effect InAs heat conduction

Large thermal biasing of individual gated nanostructures

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Nano Research 2014年第4期7卷 579-587页

作者： stefano roddaro Daniele Ercolani Mian Akif Safeen Francesco Rossella Vincenzo Piazza Francesco Giazotto Lucia Sorba Fabio Beltram NEST Scuola Normale Superiore and Istituto Nanoscienze-CNR Piazza S. Silvestro 121-56127 Pisa Italy Istituto Officina dei Materiali - CNR Basovizza S.S. 14 km 163.51-34149 Trieste Italy Center for Nanotechnology Innovation @NEST Istituto Italiano di Tecnologia Piazza San Silvestro 12 56127 Pisa Italy

We demonstrate very large and uniform temperature gradients up to about 1 K every 100 nm, in an architecture which is compatible with the field-effect control of the nanostructure under test. The temperature gradients demonstrated greatly exceed those typically obtainable with standard resistive heaters fabricated on top of the oxide layer. The nanoheating platform is demonstrated in the specific case of a short-nanowire device.

关键词： thermoelectric andthermomagnetic effects field effect devices nanowires

Scanning gate imaging of quantum point contacts and the origin of the 0.7 anomaly

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Nano Research 2015年第3期8卷 948-956页

作者： Andrea lagallo Nicola Paradiso stefano roddaro Christian Reichl Werner Wegscheider Giorgio Biasiol Lucia Sorba Fabio Beltram Stefan Heun National Enterprise for Nanoscience and Nanotechnology (NEST) Istituto Nanoscienze-CNR and Scuola Normale Superiore Piazza San Silvestro 12 56127 Pisa Italy Istituto Offcina dei Materiali CNR Laboratorio TASC 34149 Trieste Italy Solid State Physics Laboratory ETH Zurich Schafmattstrasse 16 8093 Zurich Switzerland

The origin of the anomalous transport feature appearing at a conductance G 0.7× （2e2/h） in quasi-lD ballistic devices-the so-called 0.7 anomaly-represents a long standing puzzle. Several mechanisms have been proposed to explain it, but a general consensus has not been achieved. Proposed explanations have been based on quantum interference, the Kondo effect, Wigner crystallization, and other phenomena. A key open issue is whether the point defects that can occur in these low-dimensional devices are the physical cause behind this conductance anomaly. Here we adopt a scanning gate microscopy technique to map individual impurity positions in several quasi-lD constrictions and correlate these with conductance characteristics. Our data demonstrate that the 0.7 anomaly can be observed irrespective of the presence of localized defects, and we conclude that the 0.7 anomaly is a fundamental property of low-dimensional systems.

关键词： two-dimensional electrongas (2-DEG) scanning gate microscopy 0.7 anomaly

InAs nanowire superconducting tunnel junctions： Quasiparticle spectroscopy, thermometry, and nanorefrigeration

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Nano Research 2017年第10期10卷 3468-3475页

作者： Jaakko Mastomaki stefano roddaro Mirko Rocci Valentina Zannier Daniele Ercolani Lucia Sorba Ilari J. Maasilta Nadia Ligato Antonio Fornieri Elia Strambini Francesco Giazotto NEST Scuola Normale Superiore and Istituto Nanoscienze-CNR Piazza S. Silvestro 12 I-55127 Pisa Italy Nanoscience Center Department of Physics University of Jyvaskyla 40014 Jyvaskyla Finland

We demonstrate an original method based on controlled oxidation for creating high-quality tunnel junctions between superconducting A1 reservoirs and InAs semiconductor nanowires （NWs）. We show clean tunnel characteristics with a current suppression by 〉4 orders of magnitude for a junction bias well below the A1 gap of △0≈ 200 μeV. The experimental data agree well with the Bardeen- Cooper-Schrieffer theoretical expectations for a superconducting tunnel junction. The studied devices employ small-scale tunnel contacts functioning as thermometers as well as larger electrodes that provide proof-of-principle active cooling of the electron distribution in the NWs. A peak refrigeration of approximately δT = 10 mK is achieved at a bath temperature of Tbath≈ 250-350 mK for our prototype devices. This method introduces important perspectives for the investigation of the thermoelectric effects in semiconductor nanostructures and for nanoscale refrigeration.

关键词： InAs nanowire superconducting tunnel junction thermometry nanorefrigeration

Complete thermoelectric benchmarking of individual InSb nanowires using combined micro-Raman and electric transport analysis

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Nano Research 2015年第12期8卷 4048-4060页

作者： Sara Yazji Eric A. Hoffman Daniele Ercolani Francesco Rossella Alessandro Pitanti Alessandro Cavalli stefano roddaro Gerhard Abstreiter Lucia Sorba Ilaria Zardo Walter Schottky Institut & Physik Department Technische Universittht MGJnchen Garching D-85748 Germany Institute for Advanced Study Technische Universitat Munchen Garching D-8S748 Germany NEST Istituto Nanoscienze-CNR and Scuola Normale Superiore Pisa 1-56127 Italy Department of Physics University of Basel CH-4055 Basel Switzerland

Nanowires （NWs） are ideal nanostructures for exploring the effects of low dimensionality and thermal conductivity suppression on thermoelectric behavior. However, it is challenging to accurately measure temperature gradients and heat flow in such systems. Here, using a combination of spatially resolved Raman spectroscopy and transport measurements, we determine all the thermoelectric properties of single Se-doped InSb NWs and quantify the figure of merit ZT. The measured laser-induced heating in the NWs and associated electrical response are well described by a 1D heat equation model. Our method allows the determination of the thermal contact resistances at the source and drain electrodes of the NW, which are negligible in our system. The measured thermoelectric parameters of InSb NWs agree well with those obtained based on field-effect transistor Seebeck measurements.

关键词： thermoelectric thermoelectric figure ofmerit Raman spectroscopy field-effect transistor measurements nanowire InSb

Incoherent non-Hermitian skin effect in photonic quantum walks

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Light(Science & Applications) 2024年第5期13卷 885-893页

作者： stefano Longhi Dipartimento di Fisica Politecnico di MilanoPiazza L.da Vinci 32I-20133 MilanoItaly IFISC(UIB-CSIC) Instituto de Fisica Interdisciplinar y Sistemas ComplejosE-07122 Palma de MallorcaSpain

The non-Hermitian skin effect describes the concentration of an extensive number of eigenstates near the boundaries of certain dissipative *** phenomenon has raised a huge interest in different areas of physics,including photonics,deeply expanding our understanding of non-Hermitian systems and opening up new avenues in both fundamental and applied aspects of topological *** skin effect has been associated to a nontrivial pointgap spectral topology and has been experimentally demonstrated in a variety of synthetic matter systems,including photonic *** most of physical models exhibiting the non-Hermitian skin effect full or partial wave coherence is generally *** we push the concept of skin effect into the fully incoherent regime and show that rather generally(but not universally)the non-Hermitian skin effect persists under dephasing *** results are illustrated by considering incoherent light dynamics in non-Hermitian photonic quantum walks.

关键词： dynamics. quantum effect

Dependence of impact regime boundaries on the initial temperatures of projectiles and targets

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Defence Technology（防务技术） 2024年第1期31卷 49-57页

作者： stefano Signetti Andreas Heine Fraunhofer-Institut für Kurzzeitdynamik Ernst-Mach-InstitutEMIErnst-Zermelo-Str.479104 Freiburg im BreisgauGermany

Towards higher impact velocities,ballistic events are increasingly determined by the material *** effects might range from moderate thermal softening to full phase *** particular,it is of great interest to quantify the conditions for incipient or full melting of metals during impact interactions,which result in a transition from still strength-affected to hydrodynamic material *** this work,we investigate to which extent the respective melting thresholds are also dependent on the initial,and generally elevated,temperatures of projectiles and targets before *** is studied through the application of a model developed recently by the authors to characterize the transition regime between high-velocity and hypervelocity impact,for which the melting thresholds of materials were used as the defining *** obtained results are expected to be of general interest for ballistic application cases where projectiles or targets are *** conditions might result,for example,from aerodynamic forces acting onto a projectile during atmospheric flight,explosive shapedcharge-jet formation or armor exposure to environmental *** performed analyses also broaden the scientific understanding of the relevance of temperature in penetration events,generally known since the 1960s,but often not considered thoroughly in impact studies.

关键词： Ballistic impact Thermal effects Metallic targets Energy partitioning Homologous temperature

Physical exercise and traumatic brain injury: is it question of time?

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Neural Regeneration Research 2024年第3期19卷 475-476页

作者： Valentina Mastrorilli stefano Farioli Vecchioli Institute of Biochemistry and Cell Biology Institute of Biochemistry and Cell BiologyNational Research Council(IBBC/CNR)MonterotondoRomeItaly Plaisant S.R.L. RomeItaly

Is it better to be safe than sorry?This Hamletic dilemma has always stimulated medical-scientific debates in numerous fields of *** among these,the preventive-therapeutic approach to the treatment of brain trauma is one of the most striking *** brain injury(TBI)is a leading cause of brain damage among young and elderly populations with a very high hospitalization and death *** is characterized by two pathologically distinct but strictly consequential phases:a first characterized by an immediate and highly variable mechanical dysfunction of the brain tissue,which involves widespread cell death and tissue degeneration,followed by a second phase which can last from days to even years depending on the severity of the TBI and the patient’s pre-existing health *** processes,including inflammatory phenomena,oxidative stress associated with metabolic,vascular,and neuro-modulatory deficits,are very often responsible for neuro-motor and psychological deficits leading to long-term disabilities(Kaur and Sharma,2018).

关键词： injury striking modulator

Integrated CO_(2)capture and reduction catalysis:Role ofγ-Al_(2)O_(3)support,unique state of potassium and synergy with copper

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Journal of Environmental Sciences 2024年第6期140卷 113-122页

作者： Donato Pinto stefano Minorello Zhouping Zhou Atsushi Urakawa Catalysis Engineering Department of Chemical EngineeringDelft University of TechnologyDelft2629HZNetherlands

Carbon dioxide capture and reduction(CCR)process emerges as an efficient catalytic strategy for CO_(2)capture and conversion to valuable chemicals.K-promoted Cu/Al_(2)O_(3)catalysts exhibited promising CO_(2)capture efficiency and highly selective conversion to syngas(CO+H_(2)).The dynamic nature of the Cu-K system at reaction conditions complicates the identification of the catalytically active phase and surface *** present work aims at more precise understanding of the roles of the potassium and copper and the contribution of the metal oxide ***γ-Al_(2)O_(3)guarantees high dispersion and destabilisation of the potassium phase,potassium and copper act synergistically to remove CO_(2)from diluted streams and promote fast regeneration of the active phase for CO_(2)capture releasing CO while passing H_(2).A temperature of 350℃is found necessary to activate H_(2)dissociation and generate the active sites for CO_(2)*** effects of synthesis parameters on the CCR activity are also described by combination of ex-situ characterisation of the materials and catalytic testing.

关键词： Carbon dioxide Carbon capture and utilisation CO_(2)capture and reduction Solid CO_(2)sorbents Heterogeneous catalysis Potassium Copper catalysts Aluminium oxide