Tunable Crossed Andreev Reflection in Bipolar Magnetic Semiconductors

Abhiram Soori; Polireddi Naveen

arxiv: 2605.15939 · v1 · pith:GHDT35KInew · submitted 2026-05-15 · ❄️ cond-mat.mes-hall · cond-mat.mtrl-sci· cond-mat.supr-con

Tunable Crossed Andreev Reflection in Bipolar Magnetic Semiconductors

Polireddi Naveen , Abhiram Soori This is my paper

Pith reviewed 2026-05-20 15:46 UTC · model grok-4.3

classification ❄️ cond-mat.mes-hall cond-mat.mtrl-scicond-mat.supr-con

keywords crossed Andreev reflectionbipolar magnetic semiconductorsnonlocal transportspin polarizationAndreev reflectionquantum correlationssuperconductor interfaces

0 comments

The pith

Aligning spin-polarized bands in bipolar magnetic semiconductor leads allows selective enhancement or suppression of crossed Andreev reflection.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that bipolar magnetic semiconductors have conduction and valence bands with opposite spin polarizations, which can be exploited to control crossed Andreev reflection at a superconductor interface. By independently tuning the chemical potentials of two separate BMS leads, the alignment of these bands with the superconductor can be adjusted to favor or block the nonlocal process in which an electron from one lead pairs with an electron from the other to form a Cooper pair. This yields a gate-controlled way to turn nonlocal electron-hole conversion on or off. A reader would care because the method links spin-dependent band structure directly to tunable nonlocal quantum correlations in a hybrid device geometry.

Core claim

In bipolar magnetic semiconductors the conduction and valence bands carry opposite spin polarizations; independent adjustment of the chemical potentials in two spatially separated leads therefore lets experimenters align or misalign these bands so that crossed Andreev reflection is either enhanced or suppressed at the superconductor interface.

What carries the argument

Independent chemical-potential tuning that aligns or misaligns the oppositely spin-polarized conduction and valence bands of the two BMS leads with the superconductor pairing.

If this is right

Nonlocal conductance can be switched between high and low values by gate voltages applied separately to each BMS lead.
Nonlocal electron-hole correlations become electrically controllable without altering the superconductor itself.
The same band-alignment principle can be used to select between local and crossed Andreev processes in the same device.
Hybrid structures can be designed in which spin-dependent band engineering directly dictates the strength of superconducting correlations.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The approach may extend to other nonlocal phenomena that rely on spin matching at superconductor interfaces.
Realization would benefit from materials in which BMS band polarizations have already been verified by spectroscopy.
Multi-terminal extensions could allow simultaneous control of several CAR channels for more complex entangled states.

Load-bearing premise

The conduction and valence bands of the bipolar magnetic semiconductors have opposite spin polarizations and the chemical potentials of the two leads can be adjusted independently while maintaining a clean interface with the superconductor.

What would settle it

In a BMS-superconductor-BMS junction, if the nonlocal conductance signature of crossed Andreev reflection remains unchanged when the chemical potentials of the two leads are varied across the predicted alignment points, the claimed tunability would be ruled out.

Figures

Figures reproduced from arXiv: 2605.15939 by Abhiram Soori, Polireddi Naveen.

**Figure 3.** Figure 3: FIG. 3. (a) [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗

**Figure 4.** Figure 4: FIG. 4. (a) Local and nonlocal conductivities vs bias for up [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗

read the original abstract

Crossed Andreev reflection (CAR) is a nonlocal quantum transport phenomenon that arises at the interface between a superconductor and two spatially separated metals. In this process, an electron incident from one metal combines with another electron originating from the other metal to form a Cooper pair in the superconductor. As a consequence, a hole is emitted into the second metal, establishing a nonlocal electron-hole conversion process. In contrast to local Andreev reflection -- where electron-to-hole conversion occurs within the same region -- CAR intrinsically links two spatially separated carriers, giving rise to nonlocal correlations and quantum entanglement. In bipolar magnetic semiconductors (BMSs), the conduction and valence bands possess opposite spin polarizations. We propose to achieve tunable control of CAR by independently adjusting the chemical potentials of the two regions. By engineering the alignment of spin-polarized bands in the two BMS leads, CAR can be selectively enhanced or suppressed. This tunability enables precise manipulation of nonlocal transport, and correlated electron dynamics, offering promising prospects for spintronic and superconducting device applications.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This is a qualitative proposal for gating two BMS leads to tune CAR selectivity, but it offers no calculations or models to check if the mechanism actually works.

read the letter

The core idea here is using independent chemical-potential control in bipolar magnetic semiconductors to align their oppositely spin-polarized bands and thereby favor crossed Andreev reflection over local processes at a superconductor junction. The authors lay out how this could give a handle on nonlocal transport for spintronic applications. That combination of BMS properties with CAR tuning is not something I have seen spelled out before in exactly this way, so the specific proposal counts as new even if it stays at the level of band-alignment arguments. The write-up is direct about the motivation and the potential device relevance, which makes the concept easy to grasp. The main limitation is the absence of any explicit calculation. There is no Bogoliubov-de Gennes treatment, no scattering-matrix results, and no numerical check showing how chemical-potential detuning maps onto conductance changes or whether momentum and spin matching survive at realistic interfaces. The claim therefore rests entirely on standard BMS band features and the usual CAR picture without testing whether the advertised selectivity holds up. This paper is mainly for experimental groups or device-oriented theorists who are already working on hybrid superconductor-semiconductor structures and might want to try fabricating a gated BMS junction. A reader hunting for quantitative predictions or new formal tools will not find them. It is worth sending to referees because the idea is concrete enough that feedback on adding a minimal model or parameter estimates could turn it into something more useful. I would not desk-reject it outright.

Referee Report

1 major / 2 minor

Summary. The manuscript proposes a scheme for tunable crossed Andreev reflection (CAR) in a hybrid structure consisting of a superconductor contacted by two spatially separated bipolar magnetic semiconductor (BMS) leads. In BMS materials the conduction and valence bands carry opposite spin polarizations; the central claim is that independent adjustment of the chemical potentials in the two leads can be used to align these spin-polarized bands so that CAR is selectively enhanced while local Andreev reflection and normal transmission are suppressed, thereby providing control over nonlocal transport and electron-hole correlations.

Significance. If the proposed tunability can be realized and verified, the work would supply a concrete materials-based route to manipulate nonlocal correlations and entanglement in superconducting heterostructures, with possible relevance to spintronic and quantum-information devices. The idea rests on standard properties of BMS and CAR but is presented as a qualitative proposal without quantitative support.

major comments (1)

[Abstract] Abstract: The central claim that independent chemical-potential tuning produces selective enhancement or suppression of CAR is stated but is not supported by any explicit calculation. No Bogoliubov-de Gennes Hamiltonian for the junction, scattering-matrix derivation, or nonequilibrium Green-function evaluation is provided to map chemical-potential detuning onto the nonlocal conductance or to demonstrate that momentum and spin matching at the interfaces actually yields the advertised selectivity.

minor comments (2)

A schematic diagram showing the relative alignment of the spin-polarized conduction and valence bands for different chemical-potential settings would substantially clarify the proposed mechanism.
The manuscript should specify the expected experimental signatures (e.g., nonlocal conductance peaks or sign changes) that would confirm the selective CAR enhancement.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their careful reading of the manuscript and for the constructive comment on the need for quantitative support. We address the major comment below and will revise the manuscript accordingly.

read point-by-point responses

Referee: [Abstract] Abstract: The central claim that independent chemical-potential tuning produces selective enhancement or suppression of CAR is stated but is not supported by any explicit calculation. No Bogoliubov-de Gennes Hamiltonian for the junction, scattering-matrix derivation, or nonequilibrium Green-function evaluation is provided to map chemical-potential detuning onto the nonlocal conductance or to demonstrate that momentum and spin matching at the interfaces actually yields the advertised selectivity.

Authors: We thank the referee for this observation. The manuscript is framed as a conceptual proposal that leverages the opposite spin polarizations of the conduction and valence bands in BMS materials to achieve tunable CAR via chemical-potential alignment. While the initial version emphasizes the physical mechanism without microscopic transport calculations, we agree that explicit support would strengthen the central claim. In the revised manuscript we will add a dedicated section containing a simplified scattering-matrix treatment of the superconductor–BMS junction. This will map the chemical-potential detuning onto the nonlocal conductance, explicitly showing how spin and momentum matching at the two interfaces selectively enhances CAR while suppressing local Andreev reflection and normal transmission. revision: yes

Circularity Check

0 steps flagged

No circularity: conceptual proposal rests on standard BMS and CAR properties

full rationale

The manuscript is a conceptual proposal that invokes the known opposite spin polarizations of conduction and valence bands in bipolar magnetic semiconductors and the standard definition of crossed Andreev reflection to suggest that independent chemical-potential tuning can selectively enhance or suppress CAR. No equations, scattering-matrix derivations, BdG Hamiltonians, or fitted parameters appear in the provided text; consequently no step reduces a claimed prediction to an input by construction, no self-citation chain is load-bearing, and no ansatz is smuggled in. The central claim is therefore independent of its own framing and receives the default non-circularity finding.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The proposal rests on the domain assumption that BMS materials exhibit opposite spin polarizations in conduction and valence bands; no free parameters or new entities are introduced.

axioms (1)

domain assumption Bipolar magnetic semiconductors possess conduction and valence bands with opposite spin polarizations.
Invoked directly in the abstract as the key material property enabling band-alignment control.

pith-pipeline@v0.9.0 · 5722 in / 1068 out tokens · 47931 ms · 2026-05-20T15:46:08.654160+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

We consider a two-dimensional BMS described by the Hamiltonian Hk = (ℏ²k²/2m + b) σz τz − μb τz … We use Landauer-Büttiker scattering formalism
IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

?

unclear
Relation between the paper passage and the cited Recognition theorem.

By engineering the alignment of spin-polarized bands in the two BMS leads, CAR can be selectively enhanced or suppressed

What do these tags mean?

matches: The paper's claim is directly supported by a theorem in the formal canon.
supports: The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

Works this paper leans on

23 extracted references · 23 canonical work pages

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L. Hofstetter, S. Csonka, J. Nyg˚ ard, and C. Schoenen- berger, Cooper pair splitter realized in a two-quantum- dot Y-junction, Nature461, 960 (2009)

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X. Li, X. Wu, Z. Li, J. Yang, and J. G. Hou, Bipolar magnetic semiconductors: a new class of spintronics ma- terials, Nanoscale4, 5680 (2012)

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J. Deng, J. Guo, H. Hosono, T. Ying, and X. Chen, Two- dimensional bipolar ferromagnetic semiconductors from layered antiferromagnets, Phys. Rev. Mater.5, 034005 (2021)

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J. Li, X. Li, and J. Yang, A review of bipolar magnetic semiconductors from theoretical aspects, Fundamental Research2, 511 (2022)

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J. Chen, X. Wang, Y. An, and S.-J. Gong, Recent progress in 2d bipolar magnetic semiconductors, J. Phys.: Condens. Matter36, 083001 (2023)

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Z.-X. Pang, Y. Wang, W. xiao Ji, and P. Li, Bipolar magnetic semiconductor materials based on 2D Fe2O3 lattice, Chemical Physics , 111058 (2020)

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Li and J

X. Li and J. Yang, Bipolar magnetic materials for electri- cal manipulation of spin-polarization orientation, Phys. Chem. Chem. Phys.15, 15793 (2013)

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Y. Li, J. Deng, Y.-F. Zhang, X. Jin, W.-H. Dong, J.-T. Sun, J. Pan, and S. Du, Nonvolatile electrical control of spin polarization in the 2d bipolar magnetic semiconduc- tor vsef, npj Computational Materials9, 50 (2023)

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Liu, X.-C

H.-Y. Liu, X.-C. Jiang, X.-F. Ouyang, and Y.-Z. Zhang, Half-metallicity in antiferromagneticM I 3 bilayers, Phys. Rev. B112, 024427 (2025)

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D. Beckmann, H. B. Weber, and H. v. L¨ ohneysen, Evi- dence for crossed Andreev reflection in superconductor- ferromagnet hybrid structures, Phys. Rev. Lett.93, 197003 (2004)

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M´ elin and D

R. M´ elin and D. Feinberg, Sign of the crossed con- ductances at a ferromagnet/superconductor/ferromagnet double interface, Phys. Rev. B70, 174509 (2004)

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Lipperheide and U

R. Lipperheide and U. Wille, Spin-polarized electron transport in ferromagnet/semiconductor heterostruc- tures: Unification of ballistic and diffusive transport, Phys. Rev. B72, 165322 (2005)

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Soori, Tunable crossed Andreev reflection in a het- erostructure consisting of ferromagnets, normal metal and superconductors, Solid State Commun.348-349, 114721 (2022)

A. Soori, Tunable crossed Andreev reflection in a het- erostructure consisting of ferromagnets, normal metal and superconductors, Solid State Commun.348-349, 114721 (2022)

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[20]

Das and A

S. Das and A. Soori, Crossed Andreev reflection in alter- magnets, Phys. Rev. B109, 245424 (2024)

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Soori and S

A. Soori and S. Mukerjee, Enhancement of crossed An- dreev reflection in a superconducting ladder connected to normal metal leads, Phys. Rev. B95, 104517 (2017)

work page 2017
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J. Nag, D. Rani, J. Kangsabanik, D. Singh, R. Venkatesh, P. D. Babu, K. G. Suresh, and A. Alam, Bipolar mag- netic semiconducting behavior in VNbRuAl, Phys. Rev. B104, 134406 (2021)

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C. Wen, Z. Hou, A. Akbari, K. Chen, W. Hong, H. Yang, I. Eremin, Y. Li, and H.-H. Wen, Unprecedentedly large gap in HgBa2Ca2Cu3O8+δwith the highest Tc at am- bient pressure, npj Quantum Materials10, 20 (2025)

work page 2025

[1] [1]

A. L. Yeyati, F. S. Bergeret, A. Mart´ ın-Rodero, and T. M. Klapwijk, Entangled Andreev pairs and collective excitations in nanoscale superconductors, Nat. Phys.3, 455–459 (2007)

work page 2007

[2] [2]

Recher, E

P. Recher, E. V. Sukhorukov, and D. Loss, Andreev tun- neling, Coulomb blockade, and resonant transport of non- local spin-entangled electrons, Phys. Rev. B63, 165314 (2001)

work page 2001

[3] [3]

L. G. Herrmann, F. Portier, P. Roche, A. L. Yeyati, T. Kontos, and C. Strunk, Carbon nanotubes as Cooper- pair beam splitters, Phys. Rev. Lett.104, 026801 (2010)

work page 2010

[4] [4]

Hofstetter, S

L. Hofstetter, S. Csonka, J. Nyg˚ ard, and C. Schoenen- berger, Cooper pair splitter realized in a two-quantum- dot Y-junction, Nature461, 960 (2009)

work page 2009

[5] [5]

X. Li, X. Wu, Z. Li, J. Yang, and J. G. Hou, Bipolar magnetic semiconductors: a new class of spintronics ma- terials, Nanoscale4, 5680 (2012)

work page 2012

[6] [6]

J. Deng, J. Guo, H. Hosono, T. Ying, and X. Chen, Two- dimensional bipolar ferromagnetic semiconductors from layered antiferromagnets, Phys. Rev. Mater.5, 034005 (2021)

work page 2021

[7] [7]

J. Li, X. Li, and J. Yang, A review of bipolar magnetic semiconductors from theoretical aspects, Fundamental Research2, 511 (2022)

work page 2022

[8] [8]

J. Chen, X. Wang, Y. An, and S.-J. Gong, Recent progress in 2d bipolar magnetic semiconductors, J. Phys.: Condens. Matter36, 083001 (2023)

work page 2023

[9] [9]

Z.-X. Pang, Y. Wang, W. xiao Ji, and P. Li, Bipolar magnetic semiconductor materials based on 2D Fe2O3 lattice, Chemical Physics , 111058 (2020)

work page 2020

[10] [10]

J. Deng, J. Pan, Y. Zhang, Y. Li, W. Dong, J. Sun, and S. Du, Screening and design of bipolar magnetic- semiconducting monolayers and heterostructures, ACS Applied Electronic Materials4, 3232 (2022)

work page 2022

[11] [11]

Li and J

X. Li and J. Yang, Bipolar magnetic materials for electri- cal manipulation of spin-polarization orientation, Phys. Chem. Chem. Phys.15, 15793 (2013)

work page 2013

[12] [12]

Y. Li, J. Deng, Y.-F. Zhang, X. Jin, W.-H. Dong, J.-T. Sun, J. Pan, and S. Du, Nonvolatile electrical control of spin polarization in the 2d bipolar magnetic semiconduc- tor vsef, npj Computational Materials9, 50 (2023)

work page 2023

[13] [13]

Y.-W. Son, M. Cohen, and S. Louie, Half-metallic graphene nanoribbons, Nature444, 347 (2006)

work page 2006

[14] [14]

Zhang, Y.-Y

R.-Z. Zhang, Y.-Y. Zhang, and S. Du, Design of two- dimensional half-metals with large spin gaps, Phys. Rev. B110, 085130 (2024)

work page 2024

[15] [15]

Liu, X.-C

H.-Y. Liu, X.-C. Jiang, X.-F. Ouyang, and Y.-Z. Zhang, Half-metallicity in antiferromagneticM I 3 bilayers, Phys. Rev. B112, 024427 (2025)

work page 2025

[16] [16]

Beckmann, H

D. Beckmann, H. B. Weber, and H. v. L¨ ohneysen, Evi- dence for crossed Andreev reflection in superconductor- ferromagnet hybrid structures, Phys. Rev. Lett.93, 197003 (2004)

work page 2004

[17] [17]

M´ elin and D

R. M´ elin and D. Feinberg, Sign of the crossed con- ductances at a ferromagnet/superconductor/ferromagnet double interface, Phys. Rev. B70, 174509 (2004)

work page 2004

[18] [18]

Lipperheide and U

R. Lipperheide and U. Wille, Spin-polarized electron transport in ferromagnet/semiconductor heterostruc- tures: Unification of ballistic and diffusive transport, Phys. Rev. B72, 165322 (2005)

work page 2005

[19] [19]

Soori, Tunable crossed Andreev reflection in a het- erostructure consisting of ferromagnets, normal metal and superconductors, Solid State Commun.348-349, 114721 (2022)

A. Soori, Tunable crossed Andreev reflection in a het- erostructure consisting of ferromagnets, normal metal and superconductors, Solid State Commun.348-349, 114721 (2022)

work page 2022

[20] [20]

Das and A

S. Das and A. Soori, Crossed Andreev reflection in alter- magnets, Phys. Rev. B109, 245424 (2024)

work page 2024

[21] [21]

Soori and S

A. Soori and S. Mukerjee, Enhancement of crossed An- dreev reflection in a superconducting ladder connected to normal metal leads, Phys. Rev. B95, 104517 (2017)

work page 2017

[22] [22]

J. Nag, D. Rani, J. Kangsabanik, D. Singh, R. Venkatesh, P. D. Babu, K. G. Suresh, and A. Alam, Bipolar mag- netic semiconducting behavior in VNbRuAl, Phys. Rev. B104, 134406 (2021)

work page 2021

[23] [23]

C. Wen, Z. Hou, A. Akbari, K. Chen, W. Hong, H. Yang, I. Eremin, Y. Li, and H.-H. Wen, Unprecedentedly large gap in HgBa2Ca2Cu3O8+δwith the highest Tc at am- bient pressure, npj Quantum Materials10, 20 (2025)

work page 2025