Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Zou, Yongtao; Wang, Xuebing; Chen, Ting; Li, Xuefei; Qi, Xintong; Welch, D. O.; Zhu, Pinwen; Liu, Bingbing; Cui, Tian; Li, Baosheng

doi:10.1038/srep10811

Cited by 49 publications

(51 citation statements)

References 52 publications

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“…Polycrystalline hexagonal ε -NbN bulk specimens used for the current magnetization and electrical resistivity measurements were synthesized from niobium nitride starting material (Goodfellow, claimed 99% purity) at 10 GPa and 1100∼1200 °C for 1.5 hour in a high-pressure multi-anvil apparatus at Stony Brook University. Details of this experimental setup were described elsewhere 26 27 28 29 30 31 . As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Discovery of Superconductivity in Hard Hexagonal ε-NbN

Zou

Zhang

et al. 2016

Sci Rep

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Since the discovery of superconductivity in boron-doped diamond with a critical temperature (TC) near 4 K, great interest has been attracted in hard superconductors such as transition-metal nitrides and carbides. Here we report the new discovery of superconductivity in polycrystalline hexagonal ε-NbN synthesized at high pressure and high temperature. Direct magnetization and electrical resistivity measurements demonstrate that the superconductivity in bulk polycrystalline hexagonal ε-NbN is below ∼11.6 K, which is significantly higher than that for boron-doped diamond. The nature of superconductivity in hexagonal ε-NbN and the physical mechanism for the relatively lower TC have been addressed by the weaker bonding in the Nb-N network, the co-planarity of Nb-N layer as well as its relatively weaker electron-phonon coupling, as compared with the cubic δ-NbN counterpart. Moreover, the newly discovered ε-NbN superconductor remains stable at pressures up to ∼20 GPa and is significantly harder than cubic δ-NbN; it is as hard as sapphire, ultra-incompressible and has a high shear rigidity of 201 GPa to rival hard/superhard material γ-B (∼227 GPa). This exploration opens a new class of highly desirable materials combining the outstanding mechanical/elastic properties with superconductivity, which may be particularly attractive for its technological and engineering applications in extreme environments.

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Section: Resultsmentioning

confidence: 99%

Discovery of Superconductivity in Hard Hexagonal ε-NbN

Zou

Zhang

et al. 2016

Sci Rep

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“…In numerical calculations we use parameters typical for NbN: ω D = 30meV (chosen value of ω D is some kind of compromise between variety values known for different phases of NbN [15]), k B T c = 0.86meV (T c = 10K), T = T c /2, E photon /E 0 V init = 60 (with N (0) = 25.5 eV −1 nm −3 [16], ξ = 4.8nm, d = 4nm it corresponds to E photon ≃ 1.3eV ) and neglect escape of nonequilibrium phonons to substrate because usually τ esc ≫ τ |∆| .…”

Section: Initial Stage Of Hot Spot Formationmentioning

confidence: 99%

“…The last parameters could be extracted from additional experiments where N ion , ω D , τ e−e and τ esc could be measured. Calculations of γ for NbN and WSi are based on N ion found from molar mass and density of these materials while Debye frequency is taken either from available experimental data (where it varies for different phases of NbN more than in two times [15]) or it is a result of reasonable estimation [20]. In expression for α e−e we put a = 1 (see Eq.…”

Section: Current-energy Relationmentioning

confidence: 99%

Single-Photon Detection by a Dirty Current-Carrying Superconducting Strip Based on the Kinetic-Equation Approach

2017

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Using kinetic equation approach we study dynamics of electrons and phonons in current-carrying superconducting nanostrips after absorption of single photon of near-infrared or optical range. We find that the larger the ratio Ce/C ph |T c (Tc is a critical temperature of superconductor, Ce and C ph are specific heat capacities of electrons and phonons, respectively) the larger part of photon's energy goes to electrons, they become stronger heated and, hence, could thermalize faster during initial stage of hot spot formation. Thermalization time τ th could be less then one picosecond for superconductors with Ce/C ph |T c ≫ 1 and small diffusion coefficient D ≃ 0.5cm 2 /s when thermalization occurs mainly due to electron-phonon and phonon-electron scattering in relatively small volume ∼ ξ 2 d (ξ is a superconducting coherence length, d < ξ is a thickness of the strip). At larger times because of diffusion of hot electrons effective temperature inside the hot spot decreases, the size of hot spot increases, superconducting state becomes unstable and normal domain spreads in the strip at current larger than so-called detection current. We find dependence of detection current on the photon's energy, place of its absorption in the strip, width of the strip, magnetic field and compare it with existing experiments. Our results demonstrate that materials with Ce/C ph |T c ≪ 1 are bad candidates for single photon detectors due to small transfer of photon's energy to electronic system and large τ th . We also predict that even several microns wide dirty superconducting bridge is able to detect single near-infrared or optical photon if its critical current exceeds 70 % of depairing current and Ce/C ph |T c 1.

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“…Following [31], we estimate the depairing current at zero temperature for the nanowire using I dep (0) = 1.491N (0)e (∆(0)) 3/2 (D/ ) 1/2 W d, arriving at I dep (0) ≈ 26.7 µA, where ∆(0) is the superconducting gap at zero temperature. The parameter γ is estimated to be 60 based on the acoustic properties of NbN [32]. Figure 2 shows the detection energy and detection current for a square hotbelt (L = W ) calculated from (18).…”

Section: Timing Jitter: Hotbelt Modelmentioning

confidence: 99%

“…Demagnetization effects are negligible in thin and narrow nanowires, so the vector potential A is neglected in the absence of a magnetic field. The system of equations described by (25,26,31,32) is solved numerically in one dimension. The system is first allowed to evolve to a stationary state configuration for a fixed bias current.…”

Section: A Generalized Tdgl Formulationmentioning

confidence: 99%

Intrinsic Timing Jitter and Latency in Superconducting Nanowire Single-photon Detectors

et al. 2019

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We analyze the origin of the intrinsic timing jitter in superconducting nanowire single photon detectors (SNSPDs) in terms of fluctuations in the latency of the detector response, which is determined by the microscopic physics of the photon detection process. We demonstrate that fluctuations in the physical parameters which determine the latency give rise to the intrinsic timing jitter. We develop a general description of latency by introducing the explicit time dependence of the internal detection efficiency. By considering the dynamic Fano fluctuations together with static spatial inhomogeneities, we study the details of the connection between latency and timing jitter. We develop both a simple phenomenological model and a more general microscopic model of detector latency and timing jitter based on the solution of the generalized time-dependent Ginzburg-Landau equations for the 1D hotbelt geometry. While the analytical model is sufficient for qualitative interpretation of recent data, the general approach establishes the framework for a quantitative analysis of detector latency and the fundamental limits of intrinsic timing jitter. These theoretical advances can be used to interpret the results of recent experiments measuring the dependence of detection latency and timing jitter on photon energy to the few-picosecond level.

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Hexagonal-structured ε-NbN: ultra-incompressibility, high shear rigidity and a possible hard superconducting material

Cited by 49 publications

References 52 publications

Discovery of Superconductivity in Hard Hexagonal ε-NbN

Discovery of Superconductivity in Hard Hexagonal ε-NbN

Single-Photon Detection by a Dirty Current-Carrying Superconducting Strip Based on the Kinetic-Equation Approach

Intrinsic Timing Jitter and Latency in Superconducting Nanowire Single-photon Detectors

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