Two-dimensional superconductivity and anisotropic transport at KTaO₃ (111) interfaces

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Materials

Background:

• Unconventional quantum states arise from unique electronic structures at material interfaces.
• Interfaces between oxides are known to host emergent electronic phenomena, including superconductivity.

Purpose of the Study:

• To investigate the potential for superconductivity in electron gases at interfaces involving (111)-oriented KTaO3.
• To compare the superconducting properties of KTaO3 interfaces with established systems like LaAlO3/SrTiO3.

Main Methods:

• Fabrication of interfaces between (111)-oriented KTaO3 and insulating overlayers (EuO or LaAlO3).
• Electrical transport measurements, including critical field and current-voltage characteristics.
• Temperature-dependent resistance measurements to determine superconducting transition temperatures.

Main Results:

• Discovery of superconductivity in electron gases at EuO/KTaO3 (111) and LaAlO3/KTaO3 (111) interfaces.
• Superconducting transition temperatures up to 2.2 Kelvin were observed, an order of magnitude higher than LaAlO3/SrTiO3.
• Two-dimensional nature of the superconductivity was confirmed. A distinct stripe-like phase emerged in EuO/KTaO3 (111) samples prior to superconductivity.

Conclusions:

• The (111)-oriented KTaO3 interfaces provide a novel platform for emergent superconductivity.
• The observed superconductivity is significantly enhanced compared to other oxide interfaces.
• The emergence of a stripe phase suggests complex interplay between electronic phases at these interfaces.