Pitt-led research demonstrates programmable superconducting diode at the LAO/KTO interface

A team of researchers led by the University of Pittsburgh demonstrated a programmable superconducting diode at the LaAlO3/KTaO3(LAO/KTO) interface, an advance that holds potential to enhance/help usher in the future of next-generation electronics and quantum circuits. The work, published in the journal Nano Letters, and featured on the journal’s cover, was led by first author MuqingYu, a graduate student in the lab of Jeremy Levy, Distinguished Professor of Condensed Matter Physics.

A supercurrent diode exploits the dissipationless flow of supercurrent to pass current more readily in one direction than the other—analogous to a semiconductor diode, but without resistive energy loss.

Contact Professor Levy at: jlevy@pitt.edu

The key finding–the diode’s programmability–was the result of using conductive atomic force microscope (c-AFM) lithography. The team was able to reverse the diode polarity simply by repositioning the weak link within the device, without making any changes to  the material itself. This level of control—where the superconducting circuit behavior is determined by a nanoscale “sketch” that can be erased and redrawn—demonstrated the versatility of the KTO interface as a platform for engineered quantum devices.

Using (c-AFM) lithography, the team patterned reconfigurable superconducting weak links at the LAO/KTO interface, deliberately engineering the device geometry at the nanoscale to break inversion symmetry. Under modest out-of-plane magnetic fields, these devices exhibited nonreciprocal critical currents with a rectification efficiency reaching up to 13%

Theory Reveals the Mechanism

Theoretical modeling played a critical role in understanding the observed effect. Time-dependent Ginzburg–Landau simulations, carried out in collaboration with co-author David Pekker, revealed the supercurrent diode effect was the result of asymmetric vortex motion within the inversion-symmetry-breaking device geometry. When current flowed in one direction,vortices entered and traversed the weak link more readily than when current flowed in the opposite direction, creating the observed nonreciprocity

A  Versatile Platform for Quantum Devices

This result built on a series of firsts from the Levy group at the KTO interface including the first demonstration of nanoscale conductance control (Nano Letters, 2022) and the first KTO-based superconducting quantum interference device, or SQUID (Physical Review X,2025). Together, these advances establish LAO/KTO as an adaptable, reconfigurable platform for investigating vortex dynamics and engineering quantum circuit elements, with potential applications in quantum computing and superconducting electronics.

This work represents a collaboration between the University of Pittsburgh and the University ofWisconsin–Madison. Muqing Yu (Pitt) led the experimental effort, including device fabrication using c-AFM lithography, transport measurements, data analysis, and creation of the cover art. Jieun Kim and Jiangfeng Yang (UW–Madison) grew the LAO/KTO heterostructures under the direction of Chang-Beom Eom. Ahmed Omranand Zhuan Li (Pitt) contributed to the experimental measurements. Sayanwita Biswas (Pitt) contributed to sample characterization. David Pekker (Pitt) performed the time-dependent Ginzburg–Landau simulations that were essential for identifying the vortex-based mechanism. Patrick Irvin (Pitt) contributed to the experimental infrastructure and measurement techniques. The project was directed by Jeremy Levy (Pitt)