Investigation of the Pauli paramagnetic effect in systematically tuned NbN thin films

Abstract

Superconductivity and the normal-state properties of NbN films can be tuned in a wide range, supplying a suitable platform to investigate the systematical evolution of the superconducting performances. Herein, we report the upper critical field of NbN films in both the vertical ($B\perp$ film) and parallel ($B\parallel$ film) orientations over a wide temperature range. Eight samples with the superconducting critical temperature $T_c$ ranging from 2.5 K to 9.8 K are studied. Meanwhile, the normal-state resistivity is tuned by more than six times by changing the conditions of the film growth. It is found that the magnitudes of the upper critical field in both field directions ($B_{c2}^{\perp }$ and $B_{c2}^{\parallel }$) exceed the paramagnetic limiting field $B_p$. The temperature dependent $B_{c2}^{\perp }$ can be described by the extended Werthamer--Helfand--Hohenberg (WHH) model considering the Pauli spin paramagnetism. Meanwhile, the $B_{c2}^{\parallel }$-$T$ data shows the feature of two-dimensional superconductivity in the temperature range near $T_c$. The evolution of the obtained Maki parameter with other parameters, such as the slope of the upper critical field near $T_c$ and the normal-state resistivity, are discussed to reveal the characteristics of the Pauli paramagnetic effect in this system.

arXiv comment7 pages, 6 figures

References in corpus (14)

• Evidence of Ising pairing in superconducting NbSe${}_2$ atomic layers
• Two Dimensional Ising Superconductivity in Gated MoS${}_2$
• Superconductivity protected by spin-valley locking in ion-gated MoS2
• Tuning Ising superconductivity with layer and spin-orbit coupling in two-dimensional transition-metal dichalcogenides
• Superconductivity in one dimension
• Superconducting properties and Hall Effect of epitaxial NbN thin films
• NbN superconducting nanowire single photon detector with efficiency over 90% at 1550 nm wavelength operational at compact cryocooler temperature
• Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition
• Penetration depth and tunneling studies in very thin epitaxial NbN films
• Quantized current steps due to the a.c. coherent quantum phase-slip effect
• Tunneling studies in a homogeneously disordered s-wave superconductor: NbN
• Phase diagram and upper critical field of homogenously disordered epitaxial 3-dimensional NbN films
• Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies
• Disorder-robust high-field superconducting phase of FeSe single crystals

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