Superconducting Quantum Oscillations and Anomalous Negative Magnetoresistance in a Honeycomb Nanopatterned Oxide Interface Superconductor

The extremely low superfluid density and unprecedented tunability of oxide interface superconductors provide an ideal platform for studying fluctuations in two-dimensional superconductors. In this work, we fabricate an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>LaAlO</a:mi></a:mrow><a:mn>3</a:mn></a:msub><a:mo stretchy="false">/</a:mo><a:msub><a:mrow><a:mi>KTaO</a:mi></a:mrow><a:mn>3</a:mn></a:msub></a:mrow></a:math> interface superconductor patterned with a nanohoneycomb array of insulating islands. Little-Parks-like magnetoresistance oscillations are observed, which are dictated by the superconducting flux quantum <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"><d:mrow><d:mi>h</d:mi><d:mo stretchy="false">/</d:mo><d:mn>2</d:mn><d:mi>e</d:mi></d:mrow></d:math>. Moreover, an anomalous negative magnetoresistance (ANMR) appears under a weak magnetic field, suggesting magnetic-field-enhanced superconductivity. By examining their dependences on temperature, measurement current, and electrical gating, we conclude that both phenomena are associated with superconducting order parameter: The <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi>h</g:mi><g:mo stretchy="false">/</g:mo><g:mn>2</g:mn><g:mi>e</g:mi></g:mrow></g:math> oscillations provide direct evidence of Cooper-pair transport, and the ANMR is interpreted as a consequence of multiple connected narrow superconducting paths with strong fluctuations.