Strong coupling between local moments and superconducting 'heavy' electrons in UPd2Al3

Area of Science:

• Condensed Matter Physics
• Quantum Materials
• Solid State Physics

Background:

• Heavy-fermion compounds exhibit unique electronic properties due to interactions between localized f-shell electrons and conduction electrons.
• In materials like UPd2Al3, itinerant electrons gain significant effective mass (over 100x bare electron mass).
• Superconductivity in UPd2Al3 occurs below its magnetic ordering temperature, defying conventional understanding where magnetism suppresses superconductivity.

Purpose of the Study:

• To investigate the nature of excitations in heavy-fermion superconductors.
• To understand the mechanism behind superconductivity in UPd2Al3, particularly its coexistence with magnetism.
• To explore the role of magnetic excitations in mediating superconductivity.

Main Methods:

• Detection of dispersive excitations in ordered f-electron moments.
• Analysis of the interaction between these excitations and heavy superconducting electrons.
• Integration of new findings with prior tunnelling spectroscopy measurements.

Main Results:

• Observation of a dispersive excitation, termed a 'magnetic exciton', in UPd2Al3.
• Evidence of strong coupling between these magnetic excitons and the heavy superconducting electrons.
• Correlation between magnetic excitons and superconductivity, suggesting a novel pairing mechanism.

Conclusions:

• Magnetic excitons, arising from ordered f-electron moments, interact strongly with superconducting electrons.
• These magnetic excitons may mediate effective interactions between itinerant electrons, analogous to phonons in conventional superconductors.
• This provides a potential explanation for superconductivity occurring alongside magnetism in heavy-fermion compounds like UPd2Al3.