Magnetic Quantum Criticality inside the Superconducting State Revealed by Penetration Depth Scaling with Local $T_{\mathrm{c}}$

Abstract

We demonstrate a magnetic quantum critical point embedded within the superconducting state of Zn-doped CeCoIn${}_5$, revealed by a pronounced peak in the magnetic penetration depth at zero temperature $\lambda (0)$. Using scanning SQUID microscopy, we determine the local superconducting transition temperature $T_{\mathrm{c}}$ and $\lambda (0)$. By parameterizing $\lambda (0)$ in terms of the local $T_{\mathrm{c}}$ rather than nominal Zn substitution, we circumvent the ambiguity caused by doping inhomogeneity and enable a more precise extraction of the critical exponent. The extracted exponent exceeds the clean spin-density-wave value, indicating a disorder-modified quantum critical regime. The enhancement of $\lambda (0)$ reflects the suppression of the superfluid stiffness and is consistent with critical scaling. Our approach provides a route to uncover intrinsic quantum critical behavior hidden by inhomogeneity in unconventional superconductors.

11 pages, 9 figures

References in corpus (24)

• Fermi-liquid instabilities at magnetic quantum phase transitions
• Quantum Criticality in Heavy Fermion Metals
• Heavy-fermion superconductivity in CeCoIn5 at 2.3K
• Quantum critical point lying beneath the superconducting dome in iron-pnictides
• A Sharp Peak of the Zero-Temperature Penetration Depth at Optimal Composition in BaFe2(As1-xPx)2
• Reversible Tuning of the Heavy Fermion Ground State in CeCoIn${}_5$
• Sign reversal of field-angle resolved heat capacity oscillations in a heavy fermion superconductor CeCoIn${}_5$ and $d_{x^2-y^2}$ pairing symmetry
• Kondo-Cluster-Glass State near a Ferromagnetic Quantum Phase Transition
• Scanning SQUID susceptometers with sub-micron spatial resolution
• Quantum Griffiths Phase in the weak itinerant ferromagnetic alloy Ni${}_{1-x}$V${}_x$
• Magnetic structure of Cd-doped CeCoIn5
• Scanning SQUID Susceptometry of a paramagnetic superconductor
• Enhancement of the London penetration depth in pnictides at the onset of SDW order under superconducting dome
• Non-Locality and Strong Coupling in the Heavy Fermion Superconductor CeCoIn${}_5$: A Penetration Depth Study
• CeCoIn5 - a quantum critical superfluid
• Singularity of the London penetration depth at quantum critical points in superconductors
• Nodal quasiparticle dynamics in the heavy fermion superconductor CeCoIn5 revealed by precision microwave spectroscopy
• Evolution of the superconducting energy gap structure concomitant with Fermi surface reconstruction in the heavy-fermion superconductor CeCoIn5
• Anomalous superfluid density in quantum critical superconductors
• Quantum phase transition inside the superconducting dome of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ probed by optical magneto-sensing using NV-centers in diamond
• Possible Evolution of Antiferromagnetism in Zn-Doped Heavy-Fermion Superconductor CeCoIn5
• In Situ STM Observation of Nonmagnetic Impurity Effect in MBE-grown CeCoIn${}_5$ Films
• The response of small SQUID pickup loops to magnetic fields
• Pauli-limited superconductivity and antiferromagnetism in the heavy-fermion compound CeCo(In1-xZnx)5