Thermodynamic Evidence for Pressure-Driven Evolution towards Weak-Coupling Superconductivity in Pb
1PSI Center for Neutron and Muon Sciences CNM, 5232 Villigen PSI, Switzerland.
Physical Review Letters
|July 26, 2026
Summary
High pressure suppresses strong-coupling effects in lead (Pb), as shown by muon-spin-rotation measurements. The thermodynamic critical field closely follows the superconducting gap, not the transition temperature, under pressure.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Superconductivity
Background:
- The thermodynamic critical field (B_{c}) offers insight into superconducting condensation energy.
- Pressure dependence of B_{c} is less understood than transition temperature (T_{c}).
Purpose of the Study:
- Investigate the pressure dependence of B_{c} in elemental lead (Pb).
- Thermodynamically determine the pressure evolution of the superconducting condensation energy scale.
- Clarify the relationship between B_{c}, superconducting gap (Δ(0)), and T_{c} under pressure.
Main Methods:
- Muon-spin-rotation (μSR) relaxation measurements.
- Hydrostatic pressure applied up to ~2.3 GPa.
- Determination of B_{c}(T) from magnetic-field distribution in the intermediate state.
Main Results:
- B_{c}(0) was extracted at various pressures, revealing its pressure evolution.
- The pressure dependence of B_{c}(0) more closely mirrors that of Δ(0) than T_{c}.
- The pressure derivative of the coupling ratio α = Δ(0)/(k_{B}T_{c}) aligns with the difference in pressure derivatives of B_{c}(0) and T_{c}.
Conclusions:
- Pressure suppresses strong-coupling effects in Pb.
- Results provide thermodynamic confirmation of the relationship between B_{c}, Δ(0), and T_{c}.
- Combined data suggest α approaches pressure independence under further pressure increase.
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