A5057359214- Physics of Superconductivity and Magnetism
- Superconducting and THz Device Technology
- Advanced Semiconductor Detectors and Materials
- Quantum and electron transport phenomena
- Semiconductor Quantum Structures and Devices
- Superconductivity in MgB2 and Alloys
- Radiation Detection and Scintillator Technologies
- Thermal properties of materials
- Thermal Radiation and Cooling Technologies
- Ultrasonics and Acoustic Wave Propagation
- Advanced X-ray and CT Imaging
- Spectroscopy and Laser Applications
- Mechanical and Optical Resonators
- Particle Detector Development and Performance
- Atomic and Subatomic Physics Research
- Photonic and Optical Devices
- Terahertz technology and applications
- Rare-earth and actinide compounds
- Advanced Thermodynamics and Statistical Mechanics
- Surface and Thin Film Phenomena
- Thermography and Photoacoustic Techniques
- Acoustic Wave Resonator Technologies
- Acoustic Wave Phenomena Research
- Calibration and Measurement Techniques
- Nuclear Physics and Applications
Lancaster University
2014-2023
National Institute of Standards and Technology
2021
Massachusetts Institute of Technology
2021
Jet Propulsion Laboratory
2021
SRON Netherlands Institute for Space Research
2014
Delft University of Technology
2014
European Space Research and Technology Centre
2002-2009
University of Twente
2009
Russian Academy of Sciences
1978-1993
Institute of Radio-Engineering and Electronics
1978-1991
We developed superconducting nanowire single-photon detectors based on tungsten silicide, which show saturated internal detection efficiency up to a wavelength of 10 μm. These are promising for applications in the mid-infrared requiring sub-nanosecond timing, ultra-high gain stability, low dark counts, and high efficiency, such as chemical sensing, LIDAR, matter searches, exoplanet spectroscopy.
We have developed a theory of quasiparticle and phonon energy downconversion in nonequilibrium superconductors following the absorption an energetic photon. This stage cascade is important for production quasiparticles shown to split into two phases. The first controlled by evolution distribution while second dominated downconversion. relative durations phases hence rates generation depend on material parameters, most common could be classified three different groups. For typical used x-ray...
Because of their universal nature, Fano fluctuations are expected to influence the response superconducting nanowire single-photon detectors (SNSPDs). We predict that photon counting rate ($PCR$) as a function bias current ($I_B$) in SNSPDs is described by an integral over transverse coordinate-dependent complementary error function. The latter describes smearing local responses due amount energy deposited into electronic system. finite width, $\sigma$, $PCR$ vs $I_B$ arises from partition...
We experimentally studied the dynamics of optically excited hotspots in current-carrying WSi superconducting nanowires as a function bias current, bath temperature, and excitation wavelength. observed that hotspot relaxation time depends on explained this effect with model based quasiparticle recombination, which provides insight into superconductors.
The optimization of superconducting thin-films has pushed the sensitivity nanowire single-photon detectors (SNSPDs) to mid-infrared (mid-IR). Earlier demonstrations have shown that straight tungsten silicide nanowires can achieve unity internal detection efficiency (IDE) up λ = 10 μm. For a high system (SDE), active area needs be increased, but material nonuniformity and nanofabrication-induced constrictions make mid-IR large-area meanders challenging yield. In this work, we improve...
This work presents a method to estimate experimentally the superconducting depairing current of ultrathin films by means nanowire-style resonators. Measuring allows for better determination figure merit quality nanowires. The resonance is set impedance mismatch between nanowire and transmission line. Bias dependent shifts in measured resonant frequency correspond change kinetic inductance, which can be compared with theoretical predictions resonator current. experiments lead an unexpected...
Abstract Controlling thermal transport is important for a range of devices and technologies, from phase change memories to next-generation electronics. This especially true in nano-scale where altered by the influence surfaces changes dimensionality. In superconducting nanowire single-photon detectors, boundary conductance between substrate it fabricated on influences all performance metrics that make these detectors attractive applications. includes maximum count rate, latency, jitter,...
We have developed a model for the resistive transition in edge sensor (TES) based on of resistively and capacitively shunted junction, taking into account phase-slips superconducting system across barriers tilted washing board potential. obtained analytical expressions resistance TES, R(T, I), its partial logarithmic derivatives αI βI as functions temperature current. shown that all major parameters describing state TES are determined by dependence Josephson critical current, rather than...
We describe a kinetic model of recombination nonequilibrium quasiparticles generated by single photon absorption in superconducting current-carrying nanowires. The is developed to interpret two-photon detection experiments which does not possess sufficient energy for breaking superconductivity at fixed low bias current. show that quasiparticle self-recombination relaxing hotspots dominates diffusion expansion effects and explains the observed strong current, wavelength, temperature...
We report the experimental evidence of ac Josephson effect in a transition edge sensor (TES) operating frequency domain multiplexer and biased by voltage at MHz frequencies. The is observed measuring non-linear impedance sensor. TES treated as weakly linked superconducting system within resistively shunted junction model framework. provide full theoretical explanation results finding analytic solution non-inertial Langevian equation calculating response detector to large bias current presence noise.
Generic properties of elastic phonon transport at a disordered interface are studied. The results show that transmittance is strong function frequency and the disorder correlation length. At frequencies lower than van Hove singularity given increases as length decreases. low frequencies, this reflected by different power laws for conductance across correlated uncorrelated interfaces which in approximate agreement with perturbation theory an continuum. These can be understood terms simple...
When energy is deposited in a thin-film cryogenic detector, such as from the absorption of an x-ray, important feature that determines resolution amount athermal can be lost to heat bath prior elementary excitation systems coming into thermal equilibrium. This form loss will position dependent and therefore limit detector resolution. An understanding physical processes occur when excitations are generated metal films on dielectric substrates for design optimization number different types...
We developed the model of internal phonon bottleneck to describe energy exchange between acoustically soft ultrathin metal film and rigid substrate. Discriminating phonons in into two groups, escaping nonescaping, we show that electrons nonescaping may form a unified subsystem, which is cooled down only due interactions with phonons, either direct conversion or indirect sequential interaction an electronic system. Using amplitude-modulated absorption sub-THz radiation technique, studied...
We present the results of a detailed experimental study polarization effects in thallium bromide planar x-ray detectors. Measurements were carried out range 10–100 keV by scanning highly focused beam, 50 μm diameter, from synchrotron source across detector. Above certain radiation threshold detector response showed systematic degradation its spectroscopic characteristics, peak channel position, height, and energy resolution. Using pump-and-probe technique, we studied dynamics spectral...
We have developed a model describing the non-proportional response in scintillators based on non-thermalised carrier and phonon transport. show that thermalization of e-h distributions produced immediately after photon absorption may take longer than period over which signal forms. The LO-phonon during this remain non-degenerate at quasi-equilibrium temperatures far exceeding room temperature. solve balance equations energy exchange hot bipolar plasma electrons/holes phonons. Taking into...
The topic of latency in superconducting nanowire single-photon detectors (SNSPDs, the fastest type such sensors) is interest for understanding absolute limits timing performance these devices, but so far no model detection mechanism could quantitatively explain recent measurements intrinsic jitter and latency. This analysis connection between detector presence Fano fluctuations spatial nonuniformity provides a framework studying SNSPDs, suggests that be reduced by enhancing scattering to...
We demonstrate a multilayer nanoscale cryogenic heater-based switch (M-hTron) that uses normal-metal heater overlapping thin-film superconductor separated by thin insulating layer. The M-hTron eliminates leakage current found in three-terminal superconducting switches and applies heat locally to the superconductor, reducing energy required device. Modeling using energy-balance equations acoustic mismatch model demonstrates reasonable agreement with experiment. is promising device for digital...
We present a detailed analysis of the fundamental noise sources in superconducting transition-edge sensors (TESs), ac voltage biased at MHz frequencies and treated as weak links. have studied resistive transition function bath temperature several detectors with different normal resistances geometries. show that excess noise, typically observed TES electrical bandwidth, can be explained by equilibrium Johnson quasiparticles generated within link. The fluctuations Josephson frequency higher...
We have developed a theory of photoelectron energy down-conversion in superconductors the vicinity interfaces. Significant differences from situation bulk materials arise when process takes place closer to an interface than mean free path pair-breaking phonons. Then some energetic phonons generated cascade can escape superconducting film, giving rise decrease number quasiparticles and statistical fluctuations that quantity. An additional source variability is spatial distribution initial...
We report greatly enhanced energy resolving power of Ta∕Al superconducting tunnel junction (STJ) photon detectors. The improvement in resolution has led to the observation features dependence power, which are not predicted by currently prevailing formulas. show that these effects related phonon noise generated during down-conversion electrodes, and loss on distance a absorption site from escape interface. predictions model agree well with experimental data range 0.6–6eV.