Saddle point states in two-dimensional superconducting films biased near the depairing current

Vodolazov, D. Yu.

doi:10.1103/physrevb.85.174507

Cited by 42 publications

(24 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…2 ). We note that detailed theory 20 also supports the idea that at high currents the energy saddle point is located near the edge of the film, effectively reducing the problem to a quasi-one-dimensional case.…”

Section: Discussionsupporting

confidence: 60%

“…As dark counts in wide strips have been investigated, a debate over the microscopic process by which the strips switch from the superconducting state to the normal state has emerged. Recent theories and experiments have supported three different escape processes (all of which are 2 π phase-slip events), including single vortices crossing an edge barrier 10 11 12 18 , vortex-antivortex pairs splitting apart under the action of the Lorentz force 11 13 14 15 and escape through an energy saddle point which does not involve a vortex core 19 20 21 . Such a saddle point, with a suppressed but still above zero order parameter, has been used to explain Little-type phase-slips in one-dimensional superconducting wires 22 23 .…”

mentioning

confidence: 99%

“…Such a saddle point, with a suppressed but still above zero order parameter, has been used to explain Little-type phase-slips in one-dimensional superconducting wires 22 23 . Recently, it was generalized theoretically to quasi-2D superconducting strips 20 21 . After passing through the energy saddle point, i.e.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

Murphy

Semenov

Корнеев

et al. 2015

Sci Rep

View full text Add to dashboard Cite

We perform measurements of the switching current distributions of three w ≈ 120 nm wide, 4 nm thick NbN superconducting strips which are used for single-photon detectors. These strips are much wider than the diameter of the vortex cores, so they are classified as quasi-two-dimensional (quasi-2D). We discover evidence of macroscopic quantum tunneling by observing the saturation of the standard deviation of the switching distributions at temperatures around 2 K. We analyze our results using the Kurkijärvi-Garg model and find that the escape temperature also saturates at low temperatures, confirming that at sufficiently low temperatures, macroscopic quantum tunneling is possible in quasi-2D strips and can contribute to dark counts observed in single photon detectors. At the highest temperatures the system enters a multiple phase-slip regime. In this range single phase-slips are unable to produce dark counts and the fluctuations in the switching current are reduced.

show abstract

Section: Discussionsupporting

confidence: 60%

mentioning

confidence: 99%

See 1 more Smart Citation

Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

Murphy

Semenov

Корнеев

et al. 2015

Sci Rep

View full text Add to dashboard Cite

show abstract

“…These results suggest the VPS scenario as the most likely one to occur based on a comparison of the necessary activation energies to overcome the respective saddle-points. However, there is some controversy about the validity of this approach [64,65]. First, the London-model was used for the description of vortices, which is known to fail when vortices are too close to the edge of the strip.…”

Section: Dark Countsmentioning

confidence: 99%

Detection mechanism of superconducting nanowire single-photon detectors

Engel¹,

Renema²,

Ilin³

et al. 2015

Supercond. Sci. Technol.

149

111

View full text Add to dashboard Cite

Abstract. In this paper we intend to give a comprehensive description of the current understanding of the detection mechanism in superconducting nanowire singlephoton detectors. We will review key experimental results related to the detection mechanism, e.g. the variations of the detection probability as a function of bias current, temperature or magnetic field. Commonly used detection models will be introduced and we will analyze their predictions in view of the experimental observations. Although none of the proposed detection models is able to describe all experimental data, it is becoming increasingly clear that vortices are essential for the formation of the initial normal-conducting domain that triggers a detection event.

show abstract

“…These devices consist of a thin superconducting film which detects photons when biased to a significant fraction of its critical current. Although details of the microscopic mechanism are still in dispute [3], the present understanding of this process in NbN SSPDs is as follows [4][5][6][7][8][9][10][11][12][13][14]: after the absorption of a photon, a cloud of quasiparticles is created, which is known as a hotspot. This cloud diffuses, spreading out over some area of the wire.…”

mentioning

confidence: 99%

Probing the hotspot interaction length in NbN nanowire superconducting single photon detectors

Renema

Gaudio

Wang

et al. 2017

Applied Physics Letters

View full text Add to dashboard Cite

We measure the maximal distance at which two absorbed photons can jointly trigger a detection event in NbN nanowire superconducting single photon detector (SSPD) microbridges by comparing the one-photon and two-photon efficiency of bridges of different overall lengths, from 0 to 400 nm. We find a length of 23 ± 2 nm. This value is in good agreement with to size of the quasiparticle cloud at the time of the detection event.Nanowire superconducting single photon detectors (SSPDs) [1] are a crucial technology for a variety of applications [2]. These devices consist of a thin superconducting film which detects photons when biased to a significant fraction of its critical current. Although details of the microscopic mechanism are still in dispute [3], the present understanding of this process in NbN SSPDs is as follows [4][5][6][7][8][9][10][11][12][13][14]: after the absorption of a photon, a cloud of quasiparticles is created, which is known as a hotspot. This cloud diffuses, spreading out over some area of the wire. This causes the redistribution of bias current, which triggers a vortex unbinding from the edge of the wire, if the applied bias current is such that the current for vortex entry is exceeded. The transition of a vortex across the wire creates a normal-state region, which grows under the influence of Joule heating from the bias current, leading to a measureable voltage pulse and a detection event [15].Recently, applications of these detectors have been demonstrated or proposed which rely the ability of such devices to operate as multiphoton detectors, such as multiphoton subwavelength imaging [16], ultrasensitive higher order autocorrelation [17] and near-field multiphoton sensing [18]. These applications make use of the fact that when biased at lower currents than required for single-photon detection, the detector responds only when several photons are absorbed simultaneously. This multiphoton response has moreover proven to be of great significance in investigating the question of the working mechanism of such devices.For these multiphoton applications to work, the two photons must be absorbed within some given distance of each other, which we will refer to as the hotspot interaction length s. This length determines the efficiency of an SSPD in the multiphoton regime: photons which are absorbed far away from each other along the wire will not be able to jointly cause a detection event, resulting in a reduction of the two-photon detection probability.In this work, use this effect to measure the hotspot interaction length. Our experiment is based on comparing Figure 1. a) Sketch of the experiment. Top pannel: a nanowire of length L is illuminated uniformly, and the current the nanowire is set to be in the single-photon regime. Photon absorption at any point in the wire is sufficient to cause a detection event. In the bottom pannel, the detector is in the two-photon regime, and a detection is observed only if the second photon is absorbed in the region (red spot) where an excess quasiparticle concentrati...

show abstract

Saddle point states in two-dimensional superconducting films biased near the depairing current

Cited by 42 publications

References 31 publications

Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

Three Temperature Regimes in Superconducting Photon Detectors: Quantum, Thermal and Multiple Phase-Slips as Generators of Dark Counts

Detection mechanism of superconducting nanowire single-photon detectors

Probing the hotspot interaction length in NbN nanowire superconducting single photon detectors

Contact Info

Product

Resources

About