Tuning interfacial two-component superconductivity in CoSi₂/TiSi₂ heterojunctions via TiSi₂ diffusivity

Area of Science:

• Condensed Matter Physics
• Materials Science
• Superconductivity

Background:

• Superconductor/normal-metal (S/N) heterojunctions are crucial for studying proximity effects.
• Understanding interfacial superconductivity, particularly triplet pairing, is key to advancing superconducting technologies.
• Previous research has explored Cooper pair behavior in various S/N systems, but enhanced triplet superconductivity in specific materials remains an active area.

Purpose of the Study:

• To investigate enhanced interfacial superconductivity in nonmagnetic CoSi2/TiSi2 superconductor/normal-metal planar heterojunctions.
• To detect and characterize odd-frequency spin-triplet Cooper pairs in the diffusive normal-metal component.
• To explore the tunability of transition temperature and critical field by modifying the normal-metal diffusivity.

Main Methods:

• Fabrication and characterization of T-shaped proximity junctions using CoSi2/TiSi2 heterostructures.
• Detection of odd-frequency spin-triplet Cooper pairs using transport measurements.
• Modification of the normal-metal (TiSi2) diffusivity and its effect on superconducting properties.
• Theoretical analysis using a Ginzburg-Landau model and quasi-classical theory.

Main Results:

• Observation of enhanced interfacial two-component superconductivity with a dominant triplet component.
• Detection of odd-frequency spin-triplet even-parity Cooper pairs in the diffusive TiSi2 layer.
• Tuning of transition temperature enhancement by a factor of up to 2.3 and upper critical field increase by up to a factor of 20.
• Evidence suggesting the C49 phase of TiSi2, stabilized in confined geometries, is responsible for the enhancement.

Conclusions:

• The study demonstrates a novel approach to enhance superconductivity through interfacial engineering in nonmagnetic heterojunctions.
• The findings provide direct evidence for odd-frequency triplet Cooper pairs and their role in enhanced superconducting properties.
• The results offer insights into the mechanisms behind enhanced superconductivity and relate to phenomena like the 3-K phase in Sr2RuO4.