Spin-triplet superconductivity in K₂Cr₃As₃

Area of Science:

• Condensed Matter Physics
• Superconductivity Research
• Quantum Materials

Background:

• Spin-triplet superconductors are crucial for topological quantum computing due to their ability to host Majorana bound states.
• K2Cr3As3 and its variants represent a novel class of superconductors exhibiting ferromagnetic spin fluctuations with critical temperatures up to 8 Kelvin.

Purpose of the Study:

• To experimentally confirm the spin-triplet nature of superconductivity in K2Cr3As3.
• To investigate the superconducting properties and order parameter symmetry of K2Cr3As3 single crystals.
• To explore the potential of K2Cr3As3 as a platform for topological superconductivity.

Main Methods:

• Utilizing 75As Knight shift measurements to probe spin susceptibility in K2Cr3As3 single crystals.
• Applying magnetic fields along different crystallographic axes (ab plane and c axis) below the critical temperature (Tc).
• Analyzing the field and temperature dependence of spin susceptibility to determine the superconducting order parameter.

Main Results:

• Spin susceptibility remained unchanged with in-plane magnetic fields but vanished at low temperatures for fields along the c axis.
• These results unambiguously establish K2Cr3As3 as a spin-triplet superconductor with a vector order parameter parallel to the c axis.
• The presence of a point nodal gap was also identified, further supporting topological properties.

Conclusions:

• K2Cr3As3 is confirmed as a spin-triplet superconductor, offering a new material system for fundamental research.
• The compound's properties make it a promising platform for studying topological superconductivity.
• This discovery holds potential for future technical applications in quantum computing and related fields.