Encapsulation epitaxy of air-stable 2D superconductors for quantum circuits

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Two-dimensional (2D) superconductors are crucial for quantum information science and correlated physics.
• Synthesizing large-area, air-stable monolayer 2D superconductors is challenging due to oxidation.
• Existing methods struggle with scalability and air sensitivity, hindering device fabrication.

Purpose of the Study:

• To develop a scalable method for producing air-stable, large-area monolayer niobium diselenide (1L-NbSe2).
• To investigate the potential of 1L-NbSe2 for superconducting quantum circuits.
• To demonstrate the integration of 1L-NbSe2 into functional superconducting devices.

Main Methods:

• 'Encapsulation epitaxy' growth mechanism using 2D materials (graphene, hBN) as protective templates.
• Epitaxial growth of 1L-NbSe2 underneath the encapsulation layer on various substrates.
• Development of oxidation-free transfer and superconducting edge-contact techniques for device integration.

Main Results:

• Achieved large-area ( >1 inch), air-stable 1L-NbSe2 films.
• Demonstrated robust superconductivity (Tc ≈ 1 K) and enhanced charge density waves (TCDW ≈ 177 K) in heterostructures.
• Fabricated superconducting circuits with 1L-NbSe2 exhibiting high kinetic inductance (LK ≈ 0.7 nH □⁻¹).

Conclusions:

• Encapsulation epitaxy provides a viable route for wafer-scale production of air-stable 2D superconductors.
• 1L-NbSe2 is a promising material for superconducting quantum circuits due to its properties and integration compatibility.
• This methodology paves the way for monolithic fabrication of advanced superconducting quantum devices.