Magnetic proximity-induced superconducting diode effect and infinite magnetoresistance in a van der Waals heterostructure

Letter
Open Access

Magnetic proximity-induced superconducting diode effect and infinite magnetoresistance in a van der Waals heterostructure

Jonginn Yun, Suhan Son, Jeacheol Shin, Giung Park, Kaixuan Zhang, Young Jae Shin, Je-Geun Park, and Dohun Kim

Phys. Rev. Research 5, L022064 – Published 23 June 2023

Abstract

We report unidirectional charge transport in a ${NbSe}_{2}$ noncentrosymmetric superconductor that is exchange-coupled with a ${CrPS}_{4}$ van der Waals layered antiferromagnetic insulator. The ${NbSe}_{2} / {CrPS}_{4}$ bilayer device exhibits bias-dependent superconducting critical-current variations of up to 16%, with magnetochiral anisotropy reaching $\sim 10^{5} T^{- 1} A^{- 1}$ . Furthermore, the ${CrPS}_{4} / {NbSe}_{2} / {CrPS}_{4}$ spin-valve structure exhibits the superconducting diode effect with critical-current variations of up to 40%. We also utilize the magnetic proximity effect to induce switching in the superconducting state of the spin-valve structure. Finally, it exhibits an infinite magnetoresistance ratio depending on the field sweep direction and magnetization configuration. Our result demonstrates a novel route for enhancing the nonreciprocal response in the weak external field regime ( $< 50 mT$ ) by exploiting the magnetic proximity effect.

Received 8 November 2021
Revised 29 March 2023
Accepted 25 April 2023

DOI:https://doi.org/10.1103/PhysRevResearch.5.L022064

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Electrical conductivity Proximity effect Superconductivity Transport phenomena

Noncentrosymmetric materials Superconductors

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Jonginn Yun ^1,*, Suhan Son^1,2,*, Jeacheol Shin ^1,*, Giung Park ^1,2, Kaixuan Zhang ^1,2, Young Jae Shin³, Je-Geun Park^1,2,†, and Dohun Kim ^1,‡

¹Department of Physics and Astronomy, and Institute of Applied Physics, Seoul National University, Seoul 08826, Korea
²Center for Quantum Materials, Seoul National University, Seoul 08826, Korea
³SC Devices, PsiQuantum, Palo Alto, California, 94304, USA

^*These authors contributed equally to this work.
^†Corresponding author: jgpark10@snu.ac.kr
^‡Corresponding author: dohunkim@snu.ac.kr

Article Text

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Issue

Vol. 5, Iss. 2 — June - August 2023

Subject Areas

Condensed Matter Physics

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Images

Figure 1
(a) Structure of noncentrosymmetric ${NbSe}_{2}$ . (Inset) Side view of the structure of ${NbSe}_{2}$ , where the chirality is illustrated. (b) Schematic of the valley-dependent splitting (top) and the spin-valley locking of ${NbSe}_{2}$ (bottom). The broken inversion symmetry of ${NbSe}_{2}$ introduces spin-orbit coupling, which causes valley-dependent spin-orbit splitting ( $Δ_{S O}$ ). The Zeeman splitting ( $Δ_{Z}$ ) due to the downward magnetic field causes spin-valley locking. The Fermi surfaces of the spin branches are plotted with different colors. (c) Optical microscope image of the device. The boundaries of ${NbSe}_{2}$ and ${CrPS}_{4}$ flakes are marked with violet and green lines, respectively. Beneath ${NbSe}_{2}$ were layers of antiferromagnetic ${CrPS}_{4}$ , which were placed on top of the 285-nm-thick ${SiO}_{2}$ substrate. The gold electrodes were placed on top of the ${NbSe}_{2}$ , and a four-probe measurement was conducted. The applied magnetic field was perpendicular to the substrate. The inset shows a schematic of the cross-section marked with the red dotted line.
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Figure 2
(a) Voltage drop across the ${NbSe}_{2}$ layer with respect to the current and magnetic field at $T = 1.55 K$ . The nonreciprocity and magnetochirality appear as point symmetry, as indicated by the purple dashed line. (b) I-V line cuts of Fig. 3 at 10, 20, 30, and 40 mT. The solid and dotted lines indicate the positive and negative transports direction, respectively. The line cuts are plotted near $I_{c}$ to highlight the nonreciprocal $I_{c}$ . The location of each curve in the colormap of Fig. 3 is marked with arrows of the same color. The inset shows the current-voltage characteristic with a different current sweep direction at $B = 0 T$ , where the arrows with the corresponding color indicate the current sweep direction. There is no noticeable change in $I_{c}$ , which suggests that the observed SDE is not induced by a retrapping current. (c) Dependence of $Δ I_{c}$ on the applied magnetic field. The measurement was performed by sweeping the magnetic field from positive to negative. The inset shows the dependence of $% I_{c}$ on the applied magnetic field. A maximum value of 16% was observed. (d) Magnetic-field dependence of the second-harmonic resistance. The magnetic field was swept from positive to negative. The temperature of each trace is indicated in the upper left legend. Magnetochirality was observed, and the peak location shifted to lower $B$ values as the temperature increased. (e) MCA γ was calculated from Fig. 2 using Eq. (2) with the corresponding error bar. The inset shows the temperature dependence of the resistance of the device.
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Figure 3
(a) Optical microscope image of the trilayer spin-valve device. The boundaries of ${NbSe}_{2}$ and the top (bottom) ${CrPS}_{4}$ flakes are marked with violet and green (purple) lines, respectively. Two antiferromagnetic ${CrPS}_{4}$ layers sandwiched the ${NbSe}_{2}$ layer, and the entire device was placed on top of the 285-nm-thick ${SiO}_{2}$ substrate. The gold electrodes were at the bottom of the device, and a four-probe measurement was conducted. The applied magnetic field was perpendicular to the substrate. The inset shows a cross-sectional schematic illustrating the stacking sequence. (b) Colormap of the four-probe voltage with respect to the magnetic field and the current. The magnetic field was swept from positive to negative. A drastic change in $I_{c}$ near $B = 0 T$ was observed. (c) Dependence of $Δ I_{c}$ on the applied magnetic field. The inset shows the dependence of $% I_{c}$ on the applied magnetic field. A maximum value of $\sim 40 %$ was observed. (d) Magnified colormap of the four-probe voltage near $B = 0 T$ , where the magnetic field was swept from negative to positive (top) and from positive to negative (bottom). A significant change in $I_{c}$ is clearly observed. This change produced a large MR under a well-chosen probe current, such as $I = 25 µ A$ (black dashed line). Hysteresis was also observed, which reflects the effect of ${CrPS}_{4}$ . (e) Four-point voltage as a function of the magnetic field measured with a current magnitude of $I = 25 µ A$ , where the magnetic field was swept from positive to negative (red) and from negative to positive (black). The averaged signals of five traces are plotted, with each trace collectively plotted in the background with lighter colors. The infinite MR and the hysteresis are clearly observed in the averaged curve. Stochastic switching also appears in each trace plotted in the background.
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