Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.27729

Superconducting weak links at substrate steps in bilayer nickelate films

Yidi Liu·Yaoju Tarn·Lopa Bhatt·Puhua Zhang·Joonseo Song·Berit H. Goodge·David A. Muller·Harold Y. Hwang·Yijun Yu
View original source ↗Read source document ↗Export metadata ↓

Abstract

Ambient-pressure superconductivity above 40 K has been realized in bilayer nickelate thin films on SrLaAlO$_4$ (001), yet resistive measurements often exhibit incomplete zero-resistance states and/or two-step superconducting transitions of unresolved origin. We show that these features arise from superconducting weak links at substrate step-terrace structures. A direct correlation between the azimuthal-angle-dependent two-step transition and step-terrace orientation establishes this connection, further supported by atomic-scale visualization of structurally disrupted regions at step terraces. Modeling the films as pristine (weak-link) regions with higher (lower) transition temperature reproduces essential features of the two-step transition using both a simple model and finite-element simulations. Transport measurements further reveal a strong dependence of transition characteristics - and even the occurrence of superconductivity itself - on average terrace width. These results identify step-induced weak links as the microscopic origin of two-step transitions in bilayer nickelate films, providing a framework for understanding anisotropic and percolative transport, and a route to superconducting devices.

Explore related subjects

cond-mat.supr-con

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yidi Liu, Yaoju Tarn, Lopa Bhatt, Puhua Zhang, Joonseo Song, Berit H. Goodge, David A. Muller, Harold Y. Hwang, Yijun Yu. 2026-10-20. Superconducting weak links at substrate steps in bilayer nickelate films. https://doi.org/10.1021/acs.nanolett.6c03024

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Rashba-controlled emergence and reversal of critical-field anisotropy in p-wave magnet--superconductor hybrids

We show that tuning Rashba spin-orbit coupling can change the in-plane field direction along which an $s$-wave superconductor is most susceptible to Zeeman depairing. We consider a two-dimensional $s$-wave superconductor subject to an odd-parity exchange field induced by a $p$-wave magnet. Without Rashba coupling, the out-of-plane exchange field enhances the in-plane critical field but leaves its angular response exactly isotropic, despite the anisotropic magnetic spin texture. Minimizing the Bogoliubov--de Gennes grand potential over uniform singlet pairing, we find that increasing Rashba coupling first generates and then reverses the principal-axis critical-field contrast, switching the minimum-critical-field direction by $90^{\circ}$. Equal principal-axis fields at the intervening compensation point coexist with residual angular modulation. We interpret the reversal through competing momentum-dependent depairing contributions from the magnetic and Rashba spin textures, while the on-site singlet pairing channel remains unchanged. Direction-dependent discontinuous collapses of the order parameter further shape the critical-field curves. These results identify a tunable directional paramagnetic response within the uniform-pairing sector. In heterostructures with sufficient electrostatic tunability of interfacial Rashba coupling, this reversal would enable gate control of the easy-depairing axis without reorienting the magnetic texture.

cond-mat.supr-con↗
arXiv2026

Pressure-induced superconductivity in a bilayer metal

We propose a model that explains the mechanism of pressure-induced superconductivity in a bilayer metal. Four types of pair potentials are assumed for a Cooper pair consisting of two electrons on different layers. Absence of local inversion symmetry gives rise to the spin-orbit coupling which is antisymmetric in the two layers. We assume that external pressure enhances the hybridization between the two layers. The stability of the superconducting states is well explained by the frequency symmetry of the induced pairing correlations by these potentials. Pressure-induced superconductivity emerges when the following two conditions are realized. (i) The spin-orbit coupling induces the odd-frequency pairing correlations and suppresses superconductivity at ambient pressure. (ii) The interplay between the spin-orbit coupling and the hybridization induces the additional pairing correlation that belongs to an even-frequency symmetry class. We briefly discuss the relevance of our model to real materials.

cond-mat.supr-con↗
arXiv2026

Andreev Scattering Driven Surface Photogalvanic Effect

The surface photogalvanic effect is a powerful tool for generating macroscopic direct currents in centrosymmetric film structures via asymmetric scattering of carriers at film boundaries. Here, we uncover a fundamentally distinct regime of photoinduced transport in normal metal-superconductor heterostructures, in which the macroscopic photocurrent is governed by Andreev scattering at the interface rather than by classical scattering. We demonstrate that the interplay between asymmetric surface scattering and Andreev retroreflection yields a giant, strongly frequency-dependent anomalous photocurrent. Strikingly, the electron-hole conversion at the normal-superconducting interface dictates a macroscopic sign reversal of the photogalvanic current across the superconducting transition, and induces non-analytic spectral kinks exactly at the pairing gap frequency. Our results establish the Andreev reflection-driven surface photogalvanic effect as a platform for optical control of superconducting correlations and suggest a direct, non-invasive spectroscopic probe for gap dynamics in hybrid quantum devices.

cond-mat.supr-con↗