Reconstruction of the electron-phonon interaction function in Ta, 2H-NbSe2 and MgB2 from spectra of S–c–N microcontacts

Bobrov, N. L.; Fisun, V. V.; Kvitnitskaya, O. E.; Chernobay, V. N.; Yanson, I. K.

doi:10.1063/1.4709437

Cited by 9 publications

(29 citation statements)

References 23 publications

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“…As a comparison, the diameter of the R N 0 = 1000 Ω point-contact examined in Ref. [5] is d ≈ 2 nm. Although the PC is of an S − c − S type, there is no critical current and the excess current is about 8 µA, which is substantially below the "dirty" limit.…”

Section: B Point-contacts Based On N Bse2mentioning

confidence: 94%

“…Sometimes the spectrum in the normal state does not have any phonon features because of amorphization of the material in the contact region. If the distortions affect the volume only in the center of the contact and do not extend into the depth of the material being studied, it may be possible to recover the EPI successfully from the negative contribution to the excess current [5]. In this case, it is obvious that the volumes responsible for formation of the spectra in the normal and superconducting states do not coincide in space.…”

Section: A Basic Theoretical Conceptsmentioning

confidence: 99%

“…Condition (5) means that the number of Andreev electrons varies little up to the Debye energies; this ensures a proper form for the EPI spectrum recovered from the excess current. When the excess current is strongly suppressed by nonequilibrium phonons, the shape of the spectrum can be highly distorted.…”

Section: A Basic Theoretical Conceptsmentioning

confidence: 99%

“…We have published data on EPI in N bSe 2 previously [5]. Here we consider a point-contact with a large diameter in which the condition d ξ 0 is not met.…”

Section: B Point-contacts Based On N Bse2mentioning

confidence: 99%

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Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

Bobrov

2015

Low Temperature Physics

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Nonlinear electrical effects in superconducting S − c − S contacts, including the spectroscopy of electron-phonon interactions (EPI) in these systems, and the recovery of the EPI function from experimental data are discussed. The effect of a magnetic field on the current-voltage characteristics (I-V curves) and their derivatives for ErN i2B2C point contacts (PC) with d ≥ ξ (where d is the diameter of the PC and ξ is the coherence length) is studied. It is found that in zero magnetic fields and in near-critical fields, when the size of the superconducting gap can be neglected, the position of the peaks in dV /dI coincides with the peaks in the Yanson EPI spectra. In low fields the peaks are shifted toward lower energies and in intermediate fields, the peaks split. For PC with diameters greater than or on the order of the coherence length, the relative size of the negative phonon contribution to the excess current is considerably greater than in ballistic contacts. This leads to substantial suppression of the high-frequency peaks in the spectra for the superconducting state. In order to recover the EPI function from these spectra it is necessary to correct their intensities at high energies. For dirty N bSe2 and N b point-contacts with d ≥ ξ, which have no phonon features in the second derivative of the I-V curve in the normal state, the EPI can be reconstructed from the superconducting state.

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Section: B Point-contacts Based On N Bse2mentioning

confidence: 94%

Section: A Basic Theoretical Conceptsmentioning

confidence: 99%

Section: A Basic Theoretical Conceptsmentioning

confidence: 99%

“…We have published data on EPI in N bSe 2 previously [5]. Here we consider a point-contact with a large diameter in which the condition d ξ 0 is not met.…”

Section: B Point-contacts Based On N Bse2mentioning

confidence: 99%

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Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

Bobrov

2015

Low Temperature Physics

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“…eV eV eff 0 0 [25] 、Cu、 Ag、Au等多种金属 [16] , 以及NbSe 2 和MgB 2 [26] 等化合图 3 (网络版彩图)点接触多通道机制示意图 [24] Figure 3 (Color online) Illustration of the multi-channel regime of a so-called point-contact [24]. , respectively, and it can be seen that the fine structure outside the superconducting gap can continue above the superconducting transition temperature [28].…”

Section: 点接触的制备与测量mentioning

confidence: 99%

Applications of point-contact spectroscopy in the study of topological materials

Hou¹,

Chen²,

Hao³

et al. 2021

Sci. Sin.-Phys. Mech. Astron.

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Nonequilibrium Effects in Ballistic Point Contacts Ta–Cu and 2H–NbSe2–Cu: Two-Gap Superconductivity in 2H–NbSe2

Bobrov

2024

J Low Temp Phys

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The T a − Cu and N bSe2 − Cu heterocontacts have been studied. For T a − Cu contacts the theoretical estimation of the value of δ-functional barrier at the boundary arising due to the mismatch of Fermi parameters of the contacting metals was carried out and a good agreement between the calculation and experiment was obtained. An expression for the estimation of the diameter of the heterocontact on either side of the boundary is obtained. The magnitude of the jump-like decrease in the excess current (and the superconducting gap) due to the phase transition of the superconductor region near the point contact into a spatially inhomogeneous state when the critical concentration of nonequilibrium quasiparticles is reached has been determined. Obtained dependence of the additive differential resistance on the offsets at the contact arising after the phase transition, due to the excess charge of quasiparticles and the associated reverse current (or additive voltage). In 2H − N bSe2 there is a two-zone superconductivity character with ∼8 times different energy gap values. Under the influence of current injection of nonequilibrium quasiparticles there is a sequential phase transition of the layers adjacent to the point contact into a spatially inhomogeneous state with a suppressed gap, which is accompanied by a step change in the slope of the I − V curve with a discrete increase in the differential resistance.

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Reconstruction of the electron-phonon interaction function in Ta, 2H-NbSe2 and MgB2 from spectra of S–c–N microcontacts

Cited by 9 publications

References 23 publications

Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

Inelastic electron-phonon scattering and excess current in superconducting point contacts with a short coherence length

Applications of point-contact spectroscopy in the study of topological materials

Nonequilibrium Effects in Ballistic Point Contacts Ta–Cu and 2H–NbSe2–Cu: Two-Gap Superconductivity in 2H–NbSe2

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