Infinite Magnetoresistance and Vortex Coupling in the Pb/BSCCO Heterostructure

TL;DR

This work demonstrates vortex-induced infinite magnetoresistance in Pb/BSCCO heterostructures, where an interfacial insulating PbOx layer forms a natural S/I/S' junction. By leveraging BSCCO’s vortex dynamics and cross-interface vortex coupling, the authors realize non-volatile switching between superconducting and normal states in the Pb overlayer, with butterfly-shaped hysteresis and field- and temperature-tunable behavior. The results illuminate how interfacial vortices influence superconductivity across a heterointerface and establish a transport-based platform for studying vortex interactions and potential vortex-based memory devices. The approach is scalable with Pb thickness and suggests further improvements using alternative materials to enhance device performance and fundamental understanding of interfacial superconducting vortex physics.

Abstract

Combining superconductivity with spintronics provides exciting opportunities to realize low-dissipation quantum devices. Here we report the synthesis, characterization and magnetotransport measurements of the Pb/Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (BSCCO) superconducting heterostructures, where an insulating PbO$_{x}$ layer spontaneously forms at the interface. Non-volatile switching between superconducting (logical "0") and normal ("1") states in Pb films by an external field, i.e., infinite magnetoresistance (IMR), can be realized and are attributed to the strong trapping and pinning of vortices in BSCCO. Furthermore, butterfly-shaped hysteresis loops in magnetoresistance, pronounced resistance dips/jumps and thermal reset to superconducting states can be observed and are direct manifestations of the peculiar vortex dynamics in BSCCO and vortex coupling across the Pb/BSCCO interface. Our work demonstrates a simple and effective way to realize IMR through superconducting vortices and opens up new opportunities to study the vortex interactions across the superconducting interfaces.

Figures (4)

• Figure 1: Characterization of the Pb/BSCCO heterostructure, showing the formation of an insulating PbO$_{x}$ layer at the interface. (a) Sideview of the heterostructure. Transport measurements were performed using four Au electrodes on top. (b) XRD scans of the BSCCO substrate (black), the Pb/BSCCO heterostructure (red) and a reference Pb/Si(111) sample (green). (c) ARPES spectra of a 9 Å Pb film ($\sim$3 monolayers) grown on BSCCO, obtained using 21.2 eV photons. (d) Momentum-integrated energy distribution curves (EDCs) near the Fermi level ($E_F$), obtained at the different stages of Pb deposition. (e) Shallow core-level scans of Pb films with different thicknesses grown on BSCCO. Pb $5d$ peaks from both Pb oxides and metallic Pb are labelled. (f) Temperature-dependent resistance of three Pb/BSCCO heterostructures with different Pb thicknesses. The inset shows the current flow paths (orange arrows).
• Figure 2: Magnetoresistance and its hysteresis of the Pb/BSCCO heterostructure. (a) Normalized resistance of a 100 nm Pb/BSCCO heterostructure as a function of temperature for a warming and cooling cycle under an out-of-plane magnetic field of 2 kOe. A freshly grown sample was first cooled to 2 K without a magnetic field, after which a field of 2 kOe was applied at 2 K before this measurement. (b) Magnetization–field ($M$–$H$) hysteresis loops of bulk BSCCO measured at $T$=2 K. Each loop corresponds to a specific maximal applied field (MAF) and its value is indicated on each curve. The grey circles indicate the initial $M$–$H$ curve starting from zero field (virgin curve). (c) Resistance–field ($R$-$H$) hysteresis loops at 2 K for different MAFs (their values are labelled in purple). The black circles indicate the $R$-$H$ curve during the initial field sweep, i.e., starting from a fresh superconducting state without trapped vortices. The green stars highlight the field $H_\text{Rmin}$, where the zero resistance (for low and intermediate MAF) or the minimal resistance (for high MAF) is just achieved during the downward field sweep. $H_\text{Rmin}$ is positive for low MAF and negative for intermediate MAF, see Fig. \ref{['Fig4']}(a-b). Vertical dashed lines mark the field $H_\text{c2,eff}$, where the (local) vortices in Pb films undergo dramatic changes [see Fig. \ref{['Fig4']}(d) and related discussions]. (d) The $R$-$H$ hysteresis loop under a judiciously chosen field of 6.5 kOe, where non-volatile switch of IMR can be realized. (e) Temperature-dependent resistance under zero external field after sequential warming-cooling cycles to elevated temperatures (as indicated on each curve). The sample was initially non-superconducting at 2 K, due to the application and removal of a 10 kOe field.
• Figure 3: Demonstration of the magnetic switching of superconductivity in Pb and associated IMR. (a) The $R$–$H$ hysteresis loops for a 250 nm Pb/BSCCO heterostructure. The finite-resistance state at zero field corresponds to the "1" state, while the superconducting state is the "0" state, as highlighted by red stars. (b) Demonstration of repetitive switching between the "0" and "1" states by an external field. Bottom: time-dependent magnetic field; top: the corresponding resistance. The light red and blue regions indicate the "1" and "0" states, respectively.
• Figure 4: Cartoons illustrating the vortex dynamics that underlies the observed magnetoresistance in the Pb/BSCCO heterostructure. (a-c) Vortices in the Pb/BSCCO heterostructure after an initial field sweep to a low (a), intermediate (b) and high (c) MAF. The three panels (from left to right) indicate vortices at different stages during a downward sweep from the corresponding MAF. $H_\text{Rmin}$ represents the field that has zero or minimal resistance during the downward field sweep [see green stars in Fig. \ref{['Fig2']}(c) and \ref{['Fig2']}(d)]. For low MAF (a), $H_\text{Rmin}$ is positive; for higher MAFs (b-c), $H_\text{Rmin}$ is negative. Red and blue arrows indicate vortices and anti-vortices in BSCCO, respectively. Orange dashed lines in (a,b) indicate the superconducting paths within the Pb films. (d) Vortex coupling between Pb and BSCCO near $H = \pm H_\text{c2,eff}$ [vertical dashed lines in Fig. \ref{['Fig2']}(c)], which can give rise to the observed dips/jumps in resistance [Fig. \ref{['Fig2']}(c)]. (e) Melting and annihilation of BSCCO vortices and antivortices upon warming above 20 K, which can restablish the superconducting in Pb after cooling. Note that here each vortex (or flux line) in BSCCO actually represents a vertical stack of pancake vortices, which is simplified by a vertical cylinder in this schematic plot. The soft vortex cores are represented by brown/blue circles stacked at the center of each cylinder.