[Paper Review] Suppression of Superconductivity in UPt_3 Single Crystals

J. B. Kycia, Jung‐Il Hong+4 more|arXiv (Cornell University)|Jun 23, 1998

Rare-earth and actinide compounds3 citations

TL;DR

This study investigates the suppression of superconductivity in high-quality single crystals of UPt₃ through controlled annealing, revealing an intrinsic superconducting transition temperature of 563 ± 5 mK. The observed suppression is explained by a modified Abrikosov-Gor'kov formula accounting for anisotropic pairing, Fermi surface anisotropy, and defect scattering, providing insight into unconventional superconductivity in heavy fermion systems.

ABSTRACT

High quality single crystals of UPt_3 have been prepared by vertical float-zone refining in ultra-high vacuum. We find that the superconducting transition temperature can be varied systematically by annealing, revealing that the transition temperature intrinsic to UPt_3 is 563 +/- 5 mK. The suppression of the superconducting transition from defects is consistent with a modified Abrikosov-Gor'kov formula that includes anisotropic pairing, Fermi surface anisotropy, and anisotropic scattering by defects.

Motivation & Objective

• To determine the intrinsic superconducting transition temperature (Tc) of UPt₃ by minimizing defect-induced suppression.
• To investigate how defects and disorder affect superconductivity in UPt₃ single crystals.
• To test whether the suppression of superconductivity can be described by a modified Abrikosov-Gor'kov theory incorporating anisotropic pairing and Fermi surface effects.
• To establish a systematic method for tuning Tc via controlled annealing in high-quality single crystals.

Proposed method

• High-quality single crystals of UPt₃ were grown using vertical float-zone refining under ultra-high vacuum conditions.
• The superconducting transition temperature was systematically varied by applying controlled annealing treatments.
• The observed suppression of Tc was analyzed using a modified Abrikosov-Gor'kov formula that includes anisotropic pairing and Fermi surface anisotropy.
• Defect scattering effects were incorporated into the theoretical model to account for non-uniform suppression of superconductivity.
• Theoretical fits were used to extract the intrinsic Tc by extrapolating to zero defect concentration.
• Measurements were performed to ensure consistency with the modified theory across varying defect levels.

Experimental results

Research questions

• RQ1 What is the intrinsic superconducting transition temperature of UPt₃ in the absence of defects?
• RQ2 How does defect concentration affect the superconducting transition temperature in UPt₃ single crystals?
• RQ3 Can the suppression of superconductivity be quantitatively described by a modified Abrikosov-Gor'kov theory that includes anisotropic pairing and Fermi surface effects?
• RQ4 To what extent do anisotropic scattering and Fermi surface structure influence the suppression of superconductivity in UPt₃?

Key findings

• The intrinsic superconducting transition temperature of UPt₃ is determined to be 563 ± 5 mK, representing the cleanest possible Tc for this material.
• Systematic annealing allows controlled reduction of defect concentration, enabling the extraction of the intrinsic Tc from experimental data.
• The suppression of Tc due to defects is quantitatively consistent with a modified Abrikosov-Gor'kov formula that includes anisotropic pairing and Fermi surface anisotropy.
• Anisotropic scattering by defects plays a significant role in suppressing superconductivity, indicating strong momentum-space dependence in the pairing mechanism.
• The agreement between experiment and theory supports the presence of anisotropic superconducting pairing in UPt₃.
• The results demonstrate that defect effects in heavy fermion superconductors like UPt₃ cannot be ignored and must be accounted for in theoretical modeling.