High-Efficiency and Large Supercurrent Rectification with Superconducting Coil

arXiv:2610.11259 · cond-mat.supr-con, cond-mat.mtrl-sci, physics.app-ph · Submitted 2026-10-08 · Read on arXiv

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Introduction to the show: ident: Quantum Radio. Generated commentary on the latest quantum physics and condensed matter papers.

Kai: Today's paper: "High Efficiency in Large Supercurrent Rectification with Superconducting Coil".

Mira: The gist The coil-shaped Sn10-Pb90 wire device demonstrates high rectification efficiency and large critical current difference through the compensation between an external magnetic field and the field generated by the…

Kai: First, who's behind it and why it matters.

Title and authors: Kai: Let's talk about the title of this paper, "High Efficiency in Large Supercurrent Rectification with Superconducting Coil." It immediately tells you what they’re focusing on: getting both high efficiency and a big current difference simultaneously using a coil design.

Mira: It suggests that the goal isn't just to have a diode effect, but to make it robust enough for actual power electronics where you need reliable rectification under heavy load.

Lev: From an engineering standpoint, I’m wondering if this coil geometry is practical for scaling up? Can you build a coil that handles those currents reliably without overheating or excessive magnetic field leakage?

Kai: They are specifically proposing a coil-shaped superconducting wire device concept to achieve this large diode effect by compensating the external field with the self-generated field.

Mira: It’s essentially using the way superconducting coils behave—the limitation caused by their own generated fields—to engineer a situation where current in one direction triggers the normal state while allowing a massive window in the other direction.

Lev: That sounds like a clever trick, but I need to know if it’s stable. In my field, we worry about things becoming unstable when you push the operating parameters too far outside of their designed limits.

Kai: The authors show that if you set that external field close to the critical field, even a small current in the same direction immediately causes it to go normal, while a large current window remains superconducting in the opposite direction.

Mira: This whole concept relies on those idealized conditions being achievable practically, which is where I’d want to see more assumptions unpacked.

Lev: So what’s the actual trade-off? Are we trading a simpler design for a much harder control problem when we try to implement this in a real system?

Kai: The paper suggests that the ideal parameters for this effect can be described by mathematical relationships involving the external field and the critical field, like ΔIc equals 2Ic0 times Hext over Hc <ref:2610.11259#pg2>.

Mira: Those formulas give us a way to predict how much improvement we can expect based on how you tune those magnetic fields.

Lev: So it's predictive modeling leading to experimental tuning, which is a solid path, but does the model account for all the subtle electromagnetic interactions happening inside that coil structure?

Kai: The FEM simulations they did show that the coil current itself is determined by the local maximum field in the inner edge of the wire.

Mira: And interestingly, their experimental results on coil no.two and no <ref:2610.11259#pg2>.three are quite consistent with what those simulations predicted regarding the total field at that inner edge of the wire <ref:2610.11259#pg2>.

Lev: It seems like a solid foundation for using classical electromagnetism to guide our design choices, but we still need to ensure that classical picture holds up as we move toward more complex geometries.

The paper's summary: Kai: Moving on to the actual results of this study, "High Efficiency in Large Supercurrent Rectification with Superconducting Coil," they show concrete data from testing a Sn10-Pb90 solder wire.

Mira: They report achieving an η of seventy-nine percent with a ΔIc of one hundred forty A at an external field of five hundred oersted on coil number two, and then another result with an η of eighty-four percent and a ΔIc of one hundred twenty-five A at five hundred thirty oersted on coil number three <ref:2610.11259#pg2,η of 79% with a ΔIc of 140 A at>.

Lev: Those are some substantial numbers for current testing, but what’s the caveat? Are these measurements done under standard conditions that we can really trust for practical applications?

Kai: They confirm high rectification values at large supercurrents, and they specifically highlight that the largest Ic plus value is observed around five hundred oersted for both coils <ref:2610.11259#pg2,high rectification values at large supercurrents>.

Mira: These results are presented as record-high values among the SDE studies when using conventional measurement conditions with a DC current driving it.

Lev: So we're seeing significant improvements over what was previously achieved in these sorts of diode studies, which is the main point they want to make right now.

Kai: The key takeaway here is that this coil-shaped Sn10-Pb90 SD design features a simpler physical design and higher efficiency overall, expanding what we can do with bulk-scale superconducting diodes.

Mira: It really expands the possibilities for using these diodes in larger scale applications because of how efficiently they handle those large supercurrents.

Lev: So it’s not just about getting a small current; it’s about demonstrating that you can get high efficiency at much higher currents, which is what I need to see for power electronics.

The paper's improvements: Kai: The authors suggest several ways this concept can be improved for the future. They are looking at raising the working temperature, aiming for efficiencies above sixty percent and temperatures above four point two Kelvin as a first step.

Mira: Beyond temperature, they point out that achieving higher working temperatures, like twenty or seventy-seven Kelvin, is crucial because those are the environments you need for real-world applications involving liquid hydrogen or nitrogen.

Lev: So the immediate improvement path is thermal; getting past four point two K and into liquid hydrogen territory seems like a necessary step for utility <ref:2610.11259#pg3>.

Kai: They also suggest exploring fundamentally different superconductors altogether, like Nb3Sn or cuprate wires instead of just the Sn10-Pb90 solder wire.

Mira: That shift in material—using something else entirely—is where they hope to get those higher working temperatures that are needed for next-generation devices.

Lev: If you switch materials, the whole SDE physics changes, so that means a lot more fundamental modeling is required to predict what we’ll even get.

Kai: They also suggest optimizing the coil geometry and wire parameters because the critical current Ic0 depends on both the coil shape and how many turns it has.

Mira: That gives us a clear design path: if we want to maximize the ideal critical current difference, ΔIc, we need to figure out the optimal dimensions for that coil.

Lev: So they are suggesting an AI could be used here to optimize those physical dimensions before you even start building prototypes, which is a cool idea.

Conclusion: Kai: To wrap things up on "High Efficiency in Large Supercurrent Rectification with Superconducting Coil," this paper shows that coil-shaped SDs are a viable new design strategy for giant supercurrent rectification.

Mira: They experimentally demonstrated that the coil-shaped Sn10-Pb90 wire exhibits the SDE effect, showing high η and a large ΔIc when pushed hard.

Lev: Ultimately, this work shows that this design offers a simpler design with higher efficiency and opens up possibilities for bulk-scale SDs that can be used in larger applications.

Kai: They proved that a coil-shaped Sn10-Pb90 SD with pure-Cu lead parts can achieve high η and large ΔIc, reaching seventy-nine percent efficiency with one hundred forty A difference <ref:2610.11259#pg2>.

Mira: That is a significant improvement over conventional SDs when we consider the overall performance metrics they’re presenting here.

Lev: I think this work lays a pathway for versatile superconducting power applications because of that large current capability demonstrated in this paper and I think it's going to open new pathways for what we can build with these devices.

Department of Physics, Tokyo Metropolitan University · Research Center for Energy and Environmental Materials (GREEN), National Institute for Materials Science, Tsukuba, Japan · Institute for Materials Research, Tohoku University · Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba

cond-mat.supr-con, cond-mat.mtrl-sci, physics.app-ph

Submitted: 2026-10-08

Updated: 2026-10-13

Comments: 25 page, 4 figures, SI

License: http://creativecommons.org/licenses/by/4.0/

Importance score: 79/100

The gist: The gist The coil-shaped Sn10-Pb90 wire device demonstrates high rectification efficiency and large critical current difference through the compensation between an external magnetic field and the

Key concepts

Superconducting Diode Effect (SDE)
The SDE is a phenomenon where a material behaves like a one-way switch for supercurrents. It allows current to flow easily in one direction (forward) but blocks it in the reverse direction, similar to how a regular diode works, but at superconducting currents.
Coil-shaped Superconducting Wire Device
This is the proposed physical design where a superconducting wire is shaped into a coil. This shape allows for the compensation between an external magnetic field and the magnetic field created by the coil itself, which is key to inducing a large SDE effect.
Rectification Efficiency ($\eta$)
This measures how effectively the device converts supercurrents flowing in one direction into a measurable voltage or current flow. A higher efficiency means less energy loss during the rectification process, indicating better performance for power applications.
Critical Current Difference ($\Delta I_c$)
This is the difference between the maximum supercurrent that flows in one direction ($I_{c+}$) and the maximum supercurrent that flows in the opposite direction ($I_{c-}$). A large $\Delta I_c$ is crucial because it signifies a wide operating window for rectification, allowing for high efficiency at large currents.

Terminology

Summary

The gist The coil-shaped Sn10-Pb90 wire device demonstrates high rectification efficiency and large critical current difference through the compensation between an external magnetic field and the field generated by the coil itself.

Concept and Design

The authors propose a coil-shaped superconducting wire device concept to induce a large SDE, arising from the compensation between an external magnetic field (Hext) and the field generated by the coil itself<ref:2610.11259#pg5>. This design utilizes the limitation of superconducting coils due to field generated by themselves as shown by Onnes<ref:2610.11259#pg5>. If Hext is set close to Hc, a small current on the direction where the generated Hin is the same as Hext (I-) would immediately result in surpassing Hc, and thus, going to the normal-conducting phase, while a large current window on the opposite direction (I+) would be available at the superconducting phase<ref:2610.11259#pg5>. The SDE parameters within this concept can ideally be described as ΔIc = 2Ic0(Hext/Hc) and η = Hext/Hc<ref:2610.11259#pg5>.

Experimental Results

The experimental measurements on coil-shaped SDs based on a Sn10-Pb90 solder wire achieved a η of 79% with a ΔIc of 140 A at Hext = 500 Oe (coil no.2) and a η of 84% with a ΔIc of 125 A at Hext = 530 Oe (coil no.3)<ref:2610.11259#pg3>. These results confirm high rectification values at large supercurrents<ref:2610.11259#pg5>. The largest Ic+ is observed at Hext 500 Oe for both coils with η = 79% and 84%, both cases record-high values among the SDE studies with conventional measurement conditions with a DC current<ref:2610.11259#pg7>.

Theoretical Modeling and Validation

Finite element method (FEM) simulations of electromagnetic fields were performed using the commercial software COMSOL Multiphysics® v. 6.4, using the classical Maxwell equations built in the magnetic fields interface of the AC/DC module<ref:2610.11259#pg6>. The simulation results show that the coil Ic is governed by local maximum field in the inner edge<ref:2610.11259#pg6>. The experimental results shown in Figure 1 are nicely explained by total field at the wire inner edge<ref:2610.11259#pg6>. The agreement of the Ic values obtained with a simplified FEM analysis shows that the working parameters of the coil-shaped SD can be estimated with low-cost computational models using classical electromagnetism<ref:2610.11259#pg6>.

Future Directions

The current working temperature is T = 4.2 K, and there is room for improvement for η > 60% and T > 4.2 K; working temperatures of T = 20 and 77 K are important for practical applications with liquid hydrogen and nitrogen<ref:2610.11259#pg8>. Further improvement of SDE properties including working temperature will improve the performance of various superconducting devices driven with a large current and be an essential tool for developing future superconducting power electronics<ref:2610.11259#pg8>. The authors suggest a potential direction for further exploration using the same concept of coil-shaped SDs using superconductors different from the Sn10-Pb90 solder such as Nb3Sn or cuprate wires that could result in higher working temperatures<ref:2610.11259#pg8>.

Conclusion

In this study, the authors propose coil-shaped SD as a new design strategy to achieve a giant supercurrent rectification and experimentally demonstrate that the coil-shaped Sn10-Pb90 wire shows SDE<ref:2610.11259#pg5>. The bulk-scale SDs presented in this work features a simpler design and higher efficiency, and expands the possibilities of bulk-scale SDs to large-scale applications<ref:2610.11259#pg8>. They demonstrate that a coil-shaped Sn10-Pb90 SD with pure-Cu lead parts exhibits high η and large ΔIc<ref:2610.11259#pg8>. The highest η values are 79% with ΔIc = 140 A (coil no.2) and 84% with ΔIc = 125 A (coil no.3), marking a significant improvement to large supercurrent SDs as well as to overall conventional SDs<ref:2610.11259#pg8>. High-performance SDs with a large ΔIc will open new pathway for versatile superconducting power applications<ref:2610.11259#pg8>.

Materials and Methods

The measurements were performed using a Sn10-Pb90 (wt.%) solder cylindrical wire with a diameter of 1.65 mm (Sasaki Solder Industry)<ref:2610.11259#pg13>. For coil no.2 and no.3, the solder wire was connected with pure-Cu wires (99.9%) with a diameter of 1.5 mm (Nilaco)<ref:2610.11259#pg8>. The transport Ic for coil no.1 was measured using the cryostat system in NIMS by a standard four-probe method using a Keithley 2182A nanovoltmeter<ref:2610.11259#pg8>. The transport Ic for coil no.2 and no.3 was measured using the cryostat system in IMR, Tohoku University, by a standard four-probe method using a Keithley 2182A nanovoltmeter<ref:2610.11259#pg8>.

References

The references listed are:

[1] J. Ma, R. Zhan, and X. Lin, Superconducting Diode Effects: Mechanisms, Materials and Applications., Adv. Phys. Res. 4 (2025): 2400180.<ref:2610.11259#pg14>.

[2] M. Nadeem, M. S. Fuhrer, and X. Wang, The superconducting diode effect., Nat. Rev. Phys. 5 (2023): 558.<ref:2610.11259#pg8>.

[3] H. Narita and T. Ono, Superconducting diode effect in artificial superlattices., JSAP Rev. (2024): 240206.<ref:2610.11259#pg8>.

[4] V. M. Edelstein, Magnetoelectric Effect in Polar Superconductors., Phys. Rev. Lett. 75 (1995): 2004.<ref:2610.11259#pg8>.

[5] F. Ando, Y. Miyasaka, T. Li, J. Ishizuka, T. Arakawa, Y. Shiota, T. Moriyama, Y. Yanase, and T. Ono, Observation of superconducting diode effect., Nature 584 (2020): 373.<ref:2610.11259#pg8>.

[6] T. Le, Z. Pan, Z. Xu, J. Liu, J. Wang, Z. Lou, X. Yang, Z. Wang, Y. Yao, C. Wu, and X. Lin, Superconducting diode effect and interference patterns in kagome CsV3Sb5., Nature 630(2024): 64.<ref:2610.11259#pg8>.

[7] Z. Wan, G. Qiu, H. Ren, Q. Qian, Y. Li, D. Xu, J. Zhou, J. Zhou, B. Zhou, L. Wang, T.-H. Yang, Z.-Sofery Huang K.-L Wang and X Duan Unconventional superconductivity in chiral molecule-TaS2 hybrid superlattices., Nature 632 (2024): 69.<ref:2610.11259#pg8>.

[8] L. Bauriedl, C. Bäuml, L. Fuchs, C. Baumgartner, N. Paulik, J. M. Bauer, K.-Q Lin, J. M Lupton T Taniguchi K Watanabe C Strunk and N Paradiso Supercurrent diode effect and magnetochiral anisotropy in few-layer NbSe2., Nat Commun 13 (2022): 4266.<ref:2610.11259#pg8>.

[9] B. Pal, A.

Improvements for AI systems

  1. No longer limited to nano- and micro-scale applications, allowing for bulk-scale superconducting diode devices suitable for large-scale superconductor applications. This enables development of bulk-scale SDs useful for large-scale superconductor applications by demonstrating high efficiency at large supercurrents.

  2. Enhanced current excitation capabilities using the coil design, as the paper states this is highly useful for developing the potential field of supercurrent power electronics. This suggests AI systems could be designed to model or control superconducting magnetic fields with greater efficiency than conventional methods.

  3. Creation of high-performance superconducting power electronics capable of highcurrent DC excitation, which is essential for applications like superconducting rotating machines and magnetic refrigeration. AI systems could optimize the control algorithms for these devices to minimize the thermal loads introduced by classical current rectification.

  4. Development of novel superconducting materials and structures by exploring concepts such as using superconductors different from the Sn10-Pb90 solder such as Nb3Sn or cuprate wires that could result in higher working temperatures. AI can accelerate the search for optimal material compositions based on predictive modeling of SDE properties at higher temperatures.

  5. Design optimization of coil geometry and wire parameters, as Ic0 depends on the coil shape and the turn number, allowing AI to suggest specific dimensions for coils that maximize the ideal critical current difference (ΔIc) and rectification efficiency (η). This directly improves the design phase of superconducting components.

Abstract

Superconducting diodes (SDs) are devices that rectify supercurrent through the difference in the superconducting critical current (Ic) between forward and reverse current directions. For bringing such SDs closer to practical superconducting power electronics applications, a combination of both high rectification efficiency (η) and a large Ic difference (ΔIc) is required. Here, we propose and demonstrate a coil-shaped superconducting wire device concept to induce a large SD effect, arising from the compensation between an external magnetic field (Hext) and the field generated by the coil itself. From transport Ic measurements on coil-shaped SDs based on a Sn10-Pb90 solder wire, we achieved a η of 79% with a ΔIc of 140 A at Hext = 500 Oe (coil #2) and a η of 84% with a ΔIc of 125 A at Hext = 530 Oe (coil #3), confirming high rectification values at large supercurrents. The large-current high-efficiency SDE in the coil-shaped SDs will be highly useful for developing the potential field of supercurrent power electronics.

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