Delicate superconductivity in nodal-line NaAlGe single crystal

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Nodal-line superconductor NaAlSi (Tc=7 K) is well-studied.
• Its counterpart, NaAlGe, does not superconduct despite similar structures.

Purpose of the Study:

• Investigate the lack of superconductivity in NaAlGe.
• Explore methods to induce superconductivity in NaAlGe.
• Understand the relationship between superconductivity and nodal-line topology.

Main Methods:

• Growth of NaAlGe single crystals.
• Hole doping via oxidation or Na extraction.
• Characterization of the ground state.
• X-ray diffraction analysis.

Main Results:

• Hole-doped NaAlGe exhibits superconductivity (Tc=1.8–3.3 K).
• Superconducting state shows zero resistivity and significant diamagnetic shielding.
• A transient structure with an expanded c-axis was observed during doping.
• No thermodynamic response was detected in heat capacity measurements.

Conclusions:

• NaAlGe can be made superconducting through hole doping.
• A transient, Na-deficient phase is linked to superconductivity.
• NaAlGe is comparable to NaAlSi for studying superconductivity and nodal-line topology.