Superconductivity and suppressed monoclinic distortion in FeTe films enabled by higher-order epitaxy

Area of Science:

• Materials Science
• Condensed Matter Physics
• Thin Film Growth

Background:

• Epitaxy typically requires matching lattice constants between films and substrates to minimize defects.
• Significant lattice mismatches can lead to higher-order epitaxy, a less explored growth mode.
• Higher-order epitaxy offers potential for novel material properties and emergent phenomena.

Purpose of the Study:

• To explore the application of higher-order epitaxy for growing single-crystalline iron telluride (FeTe) films.
• To investigate the structural and electronic properties of FeTe films grown with a specific higher-order commensurate ratio (6:5).
• To demonstrate the potential of higher-order epitaxy in controlling material properties and inducing superconductivity.

Main Methods:

• Molecular beam epitaxy (MBE) for thin film deposition.
• Scanning transmission electron microscopy (STEM) for interface analysis.
• Synchrotron X-ray diffraction (XRD) for structural characterization.

Main Results:

• Successfully grew single-crystalline FeTe films on CdTe(001) substrates using 6:5 commensurate higher-order epitaxy.
• Observed self-organized periodic interstitials at the film-substrate interface due to higher-order lattice matching.
• Found that the tetragonal-to-monoclinic structural transition in FeTe is suppressed in the grown films.
• Demonstrated substrate-selective two-dimensional superconductivity in the FeTe films, attributed to suppressed monoclinic distortion.

Conclusions:

• Higher-order epitaxy is a viable technique for fabricating high-quality thin films with controlled structures.
• The 6:5 commensurate epitaxy approach effectively suppresses detrimental structural transitions in FeTe.
• This method provides a pathway to engineer emergent phenomena like two-dimensional superconductivity through precise lattice control.