[论文解读] Altermagnetic Superconducting Diode Effect in Mn$_{3}$Pt/Nb Heterostructures

Saurav Sachin, Scheurer, Mathias S.+2 more|arXiv (Cornell University)|Jan 6, 2026

Chemical and Physical Properties of Materials被引用 1

一句话总结

tldr: Demonstrates a zero-field superconducting diode effect (SDE) in Nb proximitized by non-collinear Mn3Pt (T1 and T2 phases); diode efficiency reaches up to ~50% and is tunable by magnetic field and temperature without net magnetization.

ABSTRACT

Compensated magnetic orders that can split the spin-degeneracy of electronic bands have become a very active field of research. As opposed to spin-orbit coupling, the splitting resulting from these "altermagnets" is not a small relativistic correction and, in contrast to ferromagnets, not accompanied by a net magnetization and large stray fields. In particular, the theoretical analysis of the interplay of altermagnetism and superconductivity has taken center stage, while experimental investigations of their coexistence remain in their infancy. We here study heterostructures consisting of Nb thins films interfaced with the $T_1$ and $T_2$ phases of Mn$_3$Pt. These non-collinear magnetic states can be thought of as descendants from the same altermagnetic order in the absence of spin-orbit coupling. We demonstrate the non-trivial impact on the superconducting state of Nb, which exhibits a zero-field superconducting diode effect, despite the compensated ($T_2$) and nearly-compensated ($T_1$) magnetic order; the diode efficiencies can reach large values (up to 50$\%$). The diode effect is found to be highly sensitive to the form of the magnetic order, illustrating its potential as a symmetry probe. The complex magnetic field and temperature dependence hint at a rich interplay of multiple contributing mechanisms. Our results define a new materials paradigm for dissipationless spintronics and magnetization-free diode functionality, while motivating further exploration of non-collinear altermagnetic superconductors.

研究动机与目标

• Motivate and explore altermagnetism as a mechanism for spin-splitting without net magnetization.
• Investigate how non-collinear altermagnetic orders at Mn3Pt interfaces affect proximitized Nb superconductivity.
• Demonstrate and quantify a zero-field superconducting diode effect (SDE) in T1 and T2 Mn3Pt/Nb heterostructures.
• Assess how SDE depends on magnetic order, temperature, and external magnetic field.

提出的方法

• Fabricate Nb thin films interfaced with Mn3Pt in two non-collinear phases, T1 and T2, epitaxially on Nb(110)/Al2O3(0001).
• Pattern into Hall-bar geometries and perform four-probe I–V measurements down to 2 K under zero and applied out-of-plane fields.
• Define critical currents I_c+ and I_c− from I–V sweeps to quantify nonreciprocity via diode efficiency η=(I_c+−|I_c−|)/(I_c++|I_c−|).
• Characterize structural, magnetic, and transport properties with XRD, AFM, STM, AHE, susceptibility, and resistivity; monitor Tc suppression upon Mn3Pt coupling.
• Analyze temperature dependence of SDE and its evolution under Bz to separate contributions from superconductivity, magnetism, and vortex dynamics.

实验结果

研究问题

• RQ1 Does zero-field SDE occur in Nb proximitized by Mn3Pt Mn3Pt/T1 and Mn3Pt/T2 phases?
• RQ2 How does the SDE strength compare between T1 (nearly chiral) and T2 (compensated) altermagnetic orders?
• RQ3 How do temperature and out-of-plane magnetic field tune the diode efficiency and critical currents?
• RQ4 What is the relationship between SDE and magnetic order symmetry, canting, and Berry curvature in these heterostructures?

主要发现

• Zero-field SDE is observed for both T1 and T2 Mn3Pt/Nb, with higher efficiency in T1 (~up to 50%).
• Critical currents I_c+ and |I_c−| differ in zero field, yielding nonreciprocal transport that strengthens near Tc.
• Tc of Nb is suppressed from 8.3 K to 7.6 K upon interfacing with Mn3Pt, indicating a notable influence of altermagnetic order on superconductivity.
• SDE is enhanced by applying out-of-plane field Bz, with η showing symmetric V-shaped dependence on Bz and increasing with temperature toward Tc.
• T2 phase shows a weaker SDE (nearly one order of magnitude smaller than T1) though still present at zero field and boosted by Bz.
• I–V and dV/dI mappings reveal diode-like rectification and hysteresis behavior consistent with an underdamped superconducting junction regime.