[Paper Review] Magnetic Proximity-Induced Superconducting Diode Effect and Infinite Magnetoresistance in van der Waals Heterostructure

Jonginn Yun, Suhan Son+6 more|arXiv (Cornell University)|Nov 10, 2021

2D Materials and Applications6 references11 citations

TL;DR

This study demonstrates a magnetic proximity-induced superconducting diode effect and infinite magnetoresistance in van der Waals heterostructures composed of NbSe₂ and CrPS₄. By leveraging exchange coupling between the noncentrosymmetric superconductor NbSe₂ and the antiferromagnetic insulator CrPS₄, the device exhibits up to 40% critical-current asymmetry and a magnetoresistance ratio approaching infinity due to field-sweep direction dependence and controlled magnetization configuration.

ABSTRACT

We report unidirectional charge transport in a $\mathrm{NbSe_2}$ noncentrosymmetric superconductor, which is exchange-coupled with a $\mathrm{CrPS_4}$ van der Waals layered antiferromagnetic insulator. The $\mathrm{NbSe_2/CrPS_4}$ bilayer device exhibits bias-dependent superconducting critical-current variations of up to $16\%$, with the magnetochiral anisotropy reaching $\sim 10^5\mathrm{\ T^{-1}A^{-1}}$. Furthermore, the $\mathrm{CrPS_4/NbSe_2/CrPS_4}$ 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. 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 ($<50\mathrm{\ mT}$) by exploiting the magnetic proximity effect.

Motivation & Objective

• To explore nonreciprocal superconducting transport in van der Waals heterostructures with broken inversion symmetry.
• To investigate the role of magnetic proximity effect in inducing and tuning superconducting diode behavior.
• To achieve extreme magnetoresistance responses through controlled spin-valve configurations.
• To demonstrate field-direction-dependent switching in superconducting states for potential spintronic and quantum device applications.

Proposed method

• Fabrication of NbSe₂/CrPS₄ bilayer heterostructures via mechanical exfoliation and van der Waals assembly.
• Use of CrPS₄ as a magnetic tunnel barrier to induce exchange coupling in NbSe₂ via magnetic proximity effect.
• Implementation of a CrPS₄/NbSe₂/CrPS₄ spin-valve structure to control magnetization configuration and probe diode behavior.
• Measurement of critical current asymmetry under varying bias and magnetic field to quantify the superconducting diode effect.
• Application of field-sweep direction dependence to probe infinite magnetoresistance in the spin-valve configuration.
• Use of magnetochiral anisotropy as a metric to evaluate nonreciprocal response under weak magnetic fields.

Experimental results

Research questions

• RQ1 Can magnetic proximity coupling in van der Waals heterostructures induce a robust superconducting diode effect with significant critical-current asymmetry?
• RQ2 What is the magnitude of the magnetochiral anisotropy achievable in such systems under low magnetic fields?
• RQ3 How does the magnetization configuration in a spin-valve structure influence the superconducting state and resistance response?
• RQ4 Can the magnetic proximity effect enable switching between distinct superconducting states with divergent transport characteristics?
• RQ5 To what extent can the magnetoresistance ratio be enhanced, approaching infinity, in a controlled field-sweep protocol?

Key findings

• The NbSe₂/CrPS₄ bilayer exhibits a magnetochiral anisotropy of approximately 10⁵ T⁻¹A⁻¹, indicating strong nonreciprocal transport under weak magnetic fields.
• Critical current asymmetry reaches up to 16% in the bilayer structure due to magnetic proximity-induced spin-splitting in NbSe₂.
• In the CrPS₄/NbSe₂/CrPS₄ spin-valve configuration, critical current variations increase to 40%, demonstrating enhanced diode behavior.
• The spin-valve structure exhibits an infinite magnetoresistance ratio that depends on the direction of magnetic field sweep and initial magnetization state.
• The system shows field-sweep-dependent switching between superconducting states, enabling nonvolatile control of transport properties.
• The results confirm that magnetic proximity effect enables strong nonreciprocal responses even at sub-50 mT fields, enabling new pathways for low-power spintronic devices.