Superconductivity can be destroyed by a magnetic field with an upper bound known as the Pauli limit. Here, we report a large violation of the Pauli limit in both in-plane and perpendicular magnetic fields in ${\mathrm{La}}_{0.8}{\mathrm{Sr}}_{0.2}{\mathrm{NiO}}_2$ infinite-layer superconducting thin films. The critical field $H_{\mathrm{c}2}$ shows a clear anisotropic behavior and a pronounced upturn at ultralow temperatures, manifesting anisotropic superconductor-metal transition features. Scaling analysis near the $\mathit{T}\to 0$ quantum critical point of this transition reveals a quantum Griffiths singularity arising from quenched disorder, hallmarked by a diverging dynamic critical exponent. These quantum Griffiths singularity induced quantum fluctuations provide the origin for the pronounced $H_{\mathrm{c}2}$ upturn and represent a key intrinsic mechanism for the robust violation of the Pauli limit. Our findings establish a microscopic mechanism where heavy-fermion mass renormalization suppresses orbital pair breaking, enabling disorder-enhanced quantum fluctuations to preserve superconductivity far beyond the Pauli limit.

Close

PrevNext

View figure in article

• Critical field
• Electrical properties
• Quantum phase transitions
• Quantum transport
• Unconventional superconductors
• Transport techniques