A spin triplet supercurrent through the half-metallic ferromagnet CrO2.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Conventional superconductivity, typically involving spin singlet electron pairs, is generally incompatible with ferromagnetic materials.
• Ferromagnets rapidly decay spin singlet superconductivity due to strong magnetic exchange interactions.
• Theoretical predictions suggest spin triplet superconductivity may persist in ferromagnets.

Purpose of the Study:

• To investigate the possibility of inducing and detecting superconductivity in the ferromagnetic material chromium dioxide (CrO2).
• To determine the nature of the supercurrent (spin singlet vs. spin triplet) in a superconductor-ferromagnet heterostructure.
• To explore the potential for controlling superconducting currents with magnetization.

Main Methods:

• Fabrication of a Josephson junction incorporating the strong ferromagnet CrO2.
• Measurement of Josephson supercurrents through the CrO2 layer.
• Analysis of the supercurrent's behavior in relation to the material's magnetization.

Main Results:

• Observation of a robust Josephson supercurrent passing through the ferromagnetic CrO2.
• Inference that the observed supercurrent is carried by spin triplet Cooper pairs.
• Demonstration that the supercurrent can be switched by altering the magnetization direction.

Conclusions:

• Spin triplet superconductivity can be induced and sustained in the ferromagnet CrO2.
• The interface between the superconductor and ferromagnet facilitates the conversion of spin singlet to spin triplet pairs.
• The magnetization-tunable supercurrent opens possibilities for novel spintronic devices like magnetization-controlled Josephson junctions.