Enhancement of critical current density in a superconducting NbSe<sub>2</sub> step junction

He, Xin; Wen, Yan; Zhang, Chenhui; Lai, Zhiping; Chudnovsky, Eugene M.; Zhang, Xixiang

doi:10.1039/d0nr03902k

Cited by 5 publications

(2 citation statements)

References 48 publications

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“…Thus, the primary parameters of the superconducting state of atomically thin superconductors, (a) ground-state superconducting energy gap, ∆ ab (0); (b) relative jump in electronic specific heat at the transition temperature, ∆C γTc ; (c) ground-state in-plane London penetration depth, λ ab (0); (d) transition temperature, T c ; (e) gap-to-transition temperature ratio, 2∆ ab (0) kBTc , can be deduced from the fit of the measured J c (sf, T) to equations ( 30)- (33). Thus, the superconducting parameters of thin films of Ga [50], FeSe [50], InN [54], TaS 2 [50], PdTe 2 [55], MoS 2 [5,50], α-Mo 2 C [50], NbSe 2 [50,56], MATBG [46] and IrTe 2 [57] were deduced. However, J c (sf, T) measurements in atomically thin superconductors are perhaps one of the most challenging experiments and, more commonly, magnetoresistance data, R(T,B), are measured from which B c2,⊥ (T) and B c2,∥ (T), or solely B c2,∥ (T), can be extracted.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Talantsev¹

2022

Supercond. Sci. Technol.

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The amplitude of the ground-state superconducting energy gap Δ(0) and relative jump in the electronic specific heat at the transition temperature ΔC/γT c are the primary fundamental parameters of any superconductor. Several well-established techniques are available for measuring these values in the bulk samples. However, a limited number of techniques can be used to measure these parameters in atomically thin superconductors. Here, we propose a new approach for extracting Δ(0) and ΔC/γT c in atomically thin superconductors by utilizing the upper critical field data from perpendicular, Bc2,⊥(T) (when a magnetic field is applied perpendicular to the film surface), and parallel, Bc2,||(T) (when a magnetic field is applied in the direction parallel to the film surface), external field directions. The deduced parameters for few-layer-thick Al, Sn, NbSe2, MoS2, magic angle twisted trilayer graphene (MATTG), and WTe2 are well-matched values expected for strong- and moderately strong-coupled electron-phonon-mediated superconductors. In many reports, the enhancement of Bc2,||(0) above the Pauli-Clogston-Chandrasekhar limiting field (i.e., magnetic field required to break the Cooper pair) in atomically thin superconductors has been explained based on the assumption of exotic pairing mechanisms, for instance, Ising-type pairing. Here, we explain the observed Bc2,||(0) enhancement based on the geometrical enhancement factor that originates from the sample geometry. This approach does not assume the existence of novel exotic pairing mechanisms in atomically thin superconductors.

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Section: Introductionmentioning

confidence: 99%

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Talantsev¹

2022

Supercond. Sci. Technol.

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“…After establishing the impact of the CGT magnetization on the superconductivity of NbSe 2 , we next discuss the characterizations of the SDE in the NbSe 2 /CGT heterostructure side of device B. This device comprises a thin NbSe 2 flake (5 nm) and exhibits smaller critical currents, as expected for thinner superconductors [44]. As such, we limited the maximum applied current to below 2 mA to maintain high device quality and temperature-dependent stability.…”

Section: Resultsmentioning

confidence: 99%

Flux-pinning mediated superconducting diode effect in NbSe₂/CrGeTe₃ heterostructure

Mehrnejat,

Hatnean,

Rosamond

et al. 2024

2D Mater.

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In ferromagnet/superconductor bilayer systems, dipolar fields from the ferromagnet can create asymmetric energy barriers for the formation and dynamics of vortices through flux pinning. Conversely, the flux emanating from vortices can pin the domain walls of the ferromagnet, thereby creating asymmetric critical currents. Here, we report the observation of a superconducting diode effect in a NbSe2/CrGeTe3 van der Waals heterostructure in which the magnetic domains of CrGeTe3 control the Abrikosov vortex dynamics in NbSe2. In addition to extrinsic vortex pinning mechanisms at the edges of NbSe2, flux-pinning-induced bulk pinning of vortices can alter the critical current. This asymmetry can thus be explained by considering the combined effect of this bulk pinning mechanism along with the vortex tilting induced by the Lorentz force from the transport current in the NbSe2/CrGeTe3 heterostructure. We also provide evidence of critical current modulation by flux pinning depending on the history of the field setting procedure. Our results suggest a method of controlling the efficiency of the superconducting diode effect in magnetically coupled van der Waals superconductors, where dipolar fields generated by the magnetic layer can be used to modulate the dynamics of the superconducting vortices in the superconductors.

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Manipulation of Cooper‐Pair Tunneling via Domain Structure in a van der Waals Ferromagnetic Josephson Junction

Huang,

Li,

et al. 2024

Advanced Materials

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Ferromagnetic Josephson junctions play a key role in understanding the interplay between superconductivity and ferromagnetism in condensed matter physics. The magnetic domain structures of the ferromagnet in such junctions can significantly affect the tunneling of the superconducting Cooper pairs due to the strong interactions between Cooper pairs and local magnetic moments in the ferromagnetic tunnel barrier. However, the underlying microscopic mechanism of relevant quasiparticle tunneling processes with magnetic domain structures remains largely unexplored. Here, the manipulation of Cooper‐pair tunneling in the NbSe2/Cr2Ge2Te6/NbSe2 ferromagnetic Josephson junction is demonstrated by using a multidomain ferromagnetic barrier with anisotropic magnetic moments. The evolution of up‐, down‐magnetized domain and Bloch domain structures in Cr2Ge2Te6 barrier under external magnetic fields leads to the enhancement of the critical tunneling supercurrent and an unconventional dual‐peak feature with two local maxima in the field‐dependent critical current curve. The phenomenon of magnetic‐field‐modulated critical tunneling supercurrent can be well explained by the competition between the coherence length of tunneling Cooper pairs and the size of magnetic domain walls in Cr2Ge2Te6 barrier. This kind of ferromagnetic Josephson junction provides an intriguing material system for manipulating Cooper‐pair tunneling by tuning the local magnetic moments within magnetic Josephson junction devices.

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Enhancement of critical current density in a superconducting NbSe₂ step junction

Abstract: We investigate the transport properties of a NbSe2 step junction and verify that the enhancement of the critical current density is due to the vortex pinning at the step junction.

Cited by 5 publications

References 48 publications

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Flux-pinning mediated superconducting diode effect in NbSe₂/CrGeTe₃ heterostructure

Manipulation of Cooper‐Pair Tunneling via Domain Structure in a van der Waals Ferromagnetic Josephson Junction

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Enhancement of critical current density in a superconducting NbSe2 step junction

Abstract: We investigate the transport properties of a NbSe2 step junction and verify that the enhancement of the critical current density is due to the vortex pinning at the step junction.

Cited by 5 publications

References 48 publications

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Thermodynamic parameters of atomically thin superconductors derived from the upper critical field

Flux-pinning mediated superconducting diode effect in NbSe2/CrGeTe3 heterostructure

Manipulation of Cooper‐Pair Tunneling via Domain Structure in a van der Waals Ferromagnetic Josephson Junction

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Product

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Enhancement of critical current density in a superconducting NbSe₂ step junction

Flux-pinning mediated superconducting diode effect in NbSe₂/CrGeTe₃ heterostructure