Isotropic Quantum Griffiths Singularity in Nd0.8Sr0.2NiO2 Infinite-Layer Superconducting Thin Films,Physical Review Letters

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Isotropic Quantum Griffiths Singularity in Nd0.8Sr0.2NiO2 Infinite-Layer Superconducting Thin Films
Physical Review Letters ( IF 8.1 ) Pub Date : 2024-07-17 , DOI: 10.1103/physrevlett.133.036003
Qiang Zhao ₁ , Ting-Na Shao _{1,

2} , Wen-Long Yang ₁ , Xue-Yan Wang ₁ , Xing-Yu Chen ₁ , Mei-Hui Chen ₁ , Fang-Hui Zhu ₁ , Cheng-Xue Chen ₁ , Rui-Fen Dou ₁ , Chang-Min Xiong ₁ , Haiwen Liu _{1,

3,

4} , Jia-Cai Nie _{1,

3}

Affiliation

This work reports on the emergence of quantum Griffiths singularity (QGS) associated with the magnetic field induced superconductor-metal transition (SMT) in unconventional

{Nd}_{0.8} {Sr}_{0.2} {NiO}_{2}

infinite layer superconducting thin films. The system manifests isotropic SMT features under both in-plane and perpendicular magnetic fields. Importantly, after scaling analysis of the isothermal magnetoresistance curves, the obtained effective dynamic critical exponents demonstrate divergent behavior when approaching the zero-temperature critical point

B_{c}^{*}

, identifying the QGS characteristics. Moreover, the quantum fluctuation associated with the QGS can quantitatively explain the upturn of the upper critical field around zero temperature for both the in-plane and perpendicular magnetic fields in the phase boundary of SMT. These properties indicate that the QGS in the

{Nd}_{0.8} {Sr}_{0.2} {NiO}_{2}

superconducting thin film is isotropic. Moreover, a higher magnetic field gives rise to a metallic state with the resistance-temperature relation

R (T)

exhibiting

\ln T

dependence among the 2–10 K range and

T^{2}

dependence of resistance below 1.5 K, which is significant evidence of Kondo scattering. The interplay between isotropic QGS and Kondo scattering in the unconventional

{Nd}_{0.8} {Sr}_{0.2} {NiO}_{2}

superconductor can illustrate the important role of rare region in QGS and help to uncover the exotic superconductivity mechanism in this system.

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