Percolative Pathway to Stripe Order in KTaO3-Based Superconductivity

TL;DR

The work addresses fluctuation-dominated superconductivity in two-dimensional oxide interfaces, focusing on pronounced in-plane anisotropy and a proposed stripe-like superconducting texture in MgO/KTaO$_3$(111). By engineering interfacial disorder, the authors trace a percolative evolution from localized Cooper-pair islands to superconducting puddles and ultimately to stripes, as revealed by transport, magnetoresistance, and V–I measurements that show a BKT transition and directional vortex dynamics. The extracted stripe width is $w \approx 83$ nm and is consistent with the spin precession length set by spin–orbit coupling, highlighting SOC as a key organizing factor for stripe formation. The results establish disorder as a tunable parameter and diagnostic for emergent 2D superconductivity in SOC-rich systems, with potential relevance to other low-dimensional superconductors and oxide interfaces.

Abstract

The sensitivity of low dimensional superconductors to fluctuations gives rise to emergent behaviors beyond the conventional Bardeen Cooper Schrieffer framework. Anisotropy is one such manifestation, often linked to spatially modulated electronic states and unconventional pairing mechanisms. Pronounced in plane anisotropy recently reported at KTaO3 based oxide interfaces points to the emergence of a stripe order in superconducting phase, yet its microscopic origin and formation pathway remain unresolved. Here, we show that controlled interfacial disorder in MgO/KTaO3(111) heterostructures drives a percolative evolution from localized Cooper-pair islands to superconducting puddles and eventually to stripes. The extracted stripe width matches the spin precession length, suggesting a self organized modulation governed by spin orbit coupling and lattice-symmetry breaking. These findings identify disorder as both a tuning parameter and a diagnostic probe for emergent superconductivity in two dimensional quantum materials.

Figures (4)

• Figure 1: (a) Temperature dependence of sheet resistances $R_{s}^{xx}$ and $R_{s}^{yy}$ from 300 K to 0.25 K. The insets are zoom-in views of $R_{s}^{xx}$ and $R_{s}^{yy}$ below 7 K. (b, c) $dR_{s}^{xx}/dT$ and $dR_{s}^{yy}/dT$ below 7 K to display the kinks that signal the superconducting transition onset. Normal state values for $R_{s}^{xx}$ and $R_{s}^{yy}$ are read at 4 K, denoted as $R_{N}^{x}$ and $R_{N}^{y}$, respectively.
• Figure 2: (a) Normalized MR measured at 0.25 K with $I \parallel x$. The inset is a zoom-in view of the negative MR anomaly between 1.2 T and 2.5 T. (b) $\mu_0H_{c2}$ vs. $T$ measured with $I \parallel x$. The values are read when $R_s=0.5R_N^x$, and the yellow star marks the Pauli limit. Data sets measured with $I \parallel y$ are plotted in Panels (c, d) in the same order as (a, b). (e) $V$-$I$ curves measured with $I \parallel x$. The red dashed line plots the scaling law $V \propto I^{\alpha}$ with $\alpha=3$. (f) $\alpha$ vs. $T$. The grey horinzontal line marks $\alpha=3$. The $V$-$I$ data measured with $I \parallel y$ are plotted in Panels (g, h) in the same order as (e, f).
• Figure 3: (a) Normalized $DR$ measured with $I \parallel x$ at 0.6 K. A ZBRP is resolved near $I_{dc}=0$ as shown in the inset. The peak height is denoted as $\delta R$ and the baseline is $R_{0}$. (b-e) Normalized $DR$ measured at various magnetic fields and temperatures. The insets show $DR$ vs. $I_{dc}$ along the trajectories in the same colors. (f) Dependence of peak height $\delta R/R_N$ on $r$. The arrow marks the sharp drop of $\delta R$ at r = 0.33, equivalently with $B = 1.5$ T.
• Figure 4: (a-d) Normalized MR measured with various combinations of current directions and magnetic field orientations as labelled above each panel. Data curves are vertically shifted with measurement temperatures labelled next to each curve. (e) Dependence of normalized peak height $\delta R/R_N$ on $r$. The arrow marks $r = 0.65$ beyond which $\delta R/R_N$ gradually decays. (f) Phase diagram of the superconducting transition with the isocurves $r = 0.65$ and $r=0.33$ marking the crossovers from Cooper pair islands to superconducting puddles and to stripes.