Lithium intercalated FeSe as a high-temperature superconducting ferromagnet

Area of Science:

• Condensed Matter Physics
• Materials Science

Background:

• Merging superconductivity and ferromagnetism is challenging due to their antagonistic nature.
• Achieving these properties in a single material could unlock novel quantum phenomena for advanced devices.

Purpose of the Study:

• To merge superconductivity and ferromagnetism in FeSe at record-high temperatures.
• To explore the interplay between these two phenomena and their potential applications.

Main Methods:

• Electric-field controlled lithiation of FeSe.
• In-situ gating to switch between nonmagnetic and ferromagnetic superconducting states.
• Magneto-transport measurements and scanning superconducting quantum interference device (sSQUID) microscopy.
• Density-functional theory (DFT) calculations.

Main Results:

• Superconductivity and ferromagnetism were merged in FeSe at high temperatures (up to 200 K).
• FeSe was switched between a nonmagnetic superconductor and a superconducting ferromagnet via electric-field control.
• Itinerant ferromagnetism persisted below the superconducting transition temperature (45 K).
• In-plane magnetic fields were found to enhance superconductivity, indicating a strong interplay.

Conclusions:

• Electric-field controlled lithiation is a viable method to merge superconductivity and ferromagnetism in FeSe.
• The findings open new avenues for iron-based superconductors in spintronics and dissipationless electronics.
• The intimate interplay between superconductivity and ferromagnetism at high temperatures is demonstrated.