Emergent altermagnetism in (LaVO 3) n /(LaNiO 3) m superlattices from interfacial charge transfer and octahedral tilts

arXiv:2610.30371 · cond-mat.str-el, cond-mat.mtrl-sci · Submitted 2026-10-21 · 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: We're looking at the paper: "Emergent altermagnetism in (LaVO 3) n /(LaNiO 3) m superlattices from interfacial charge transfer and octahedral tilts".

Mira: Here's the gist of the paper. The gist: Emergent altermagnetism emerges in (LaVO3)n/(LaNiO3)m superlattices from interfacial charge transfer and octahedral tilts.

Kai: How it works The emergence of altermagnetism is driven by the interplay between interfacial charge transfer and octahedral tilts in (LaVO3)n/(LaNiO3)m superlattices, leading to a C-type antiferromagnetic order combined with specific octahedral rotations that link opposite-spin sublattices only through nonsymmorphic operations, yielding a d-wave spin splitting without spin-orbit coupling The charge transfer drives the system towards the V4+ and Ni2+ configuration, turning the otherwise paramagnetic nickelate layers into a magnetically active sublattice Key Findings on Mechanism The mechanism stabilizing the C-AFM ground state is a cooperative interplay between charge transfer and symmetry The oxygen-continuity band mismatch of approximately 0.64 eV acts as the main driving force for spontaneous and directional charge transfer, indicating that electrons are transferred from the V-3d orbitals to hybridized Ni-3d - O-2p states This charge transfer quenches oxygen ligand holes and establishes the emergent V4+ (3d1) and Ni2+ (3d8) like configurations Symmetry and Magnetic Order The structural analysis reveals that the oxygen octahedra in (LVO)1/(LNO)1, (LVO)2/(LNO)2, and (LVO)2/(LNO)4 superlattices are characterized by octahedral rotations denoted as a −b+c−, a −b+c−, and a −b−c− patterns, respectively The resulting C-AFM order is the ground state for (LVO)1/(LNO)1 and (LVO)2/(LNO)2, and (LVO)2/(LNO)4 SLs The nonsymmorphic operations, specifically a twofold screw axis along c and a glide plane perpendicular to c with intrinsic translation a/2, connect the opposite spin sublattices without any translation or inversion, indicating that the altermagnetic classification (d-wave type) is preserved Spin Splitting Characteristics The resulting non-relativistic spin splitting reaches up to 117.9 meV in the insulating (LVO)1/(LNO)1 superlattice in the absence of SOC, which is about twice that calculated for bulk LaVO3 Orbital-resolved band structures show that both the vanadium and nickel sublattices host the splitting, establishing the observed altermagnetism as a collective, charge transfer driven phase distinct from a passive proximity effect The momentum-dependent spin splittings are characterized by a mixed d-wave form factor, where 27%, 28%, and 45% of the splitting weight resides on the oxygen states Design Principle The findings identify interfacial charge transfer as a design principle for engineering altermagnetic phases in oxide superlattices This route is complementary to the search for intrinsic bulk candidates, by activating otherwise nonmagnetic constituents such as LaNiO3 The confinement of (LVO)1/(LNO)1 drives the system into an insulating regime within DFT+U, with an indirect band gap of 1.62 eV The interfacial charge transfer fills the ligand holes, and the resulting Ni cations are fundamentally reconfigured to be in an active, 3d8 state The paper demonstrates that interfacial charge transfer in (LaVO3)n/(LaNiO3)m superlattices turns the paramagnetic metallic LaNiO3 layers into a magnetically active Ni2+ (3d8) sublattice that participates in an altermagnetic emergent phase The resulting spin-splitting is fixed by the nonsymmorphic spin-group symmetries, which are insensitive to such effects This route is complementary to the search for intrinsic bulk candidates.

Mira: The authors stress that this route is complementary to the search for intrinsic bulk candidates.

Kai: How it works The octahedral tilts play a dual role, narrowing the bands and stabilizing the local moments whose superexchange selects the C-AFM order, while also removing lattice translation symmetries that connect the two spin sublattices in the untilted structure The absence of these distortions restores translational symmetries connecting the sublattices and completely suppressing the momentum-dependent nonrelativistic spin splitting observed in the distorted P21/c phase.

Paper summary: Kai: So, this paper, "Emergent altermagnetism in (LaVO3)n/(LaNiO3)m superlattices from interfacial charge transfer and octahedral tilts," it's looking at how these two materials can interact to create something new.

Mira: Right, it claims that you get this altermagnetism in specific superlattices, like (one one), (two two), and (two four) <ref:2610.30371#pg1,1, 1), (2, 2), and (2, 4>. The big idea is that the interplay between charge transfer at the interface and octahedral tilts is what drives this magnetic behavior.

Lev: From a hardware standpoint, when you look at what they built—the DFT+U calculations—they show that charge transfer pushes the system toward a V4+ and Ni2+ configuration, which makes those nickelate layers magnetically active instead of just paramagnetic.

Kai: That's interesting because we usually think of the LaNiO3 layers as pretty standard, paramagnetic nickelates. So this paper suggests they can become magnetically active sublattices through these structural and electronic changes.

Mira: Exactly, and it points to a C-type antiferromagnetic order combined with specific octahedral tilts, like a minus b plus c minus or a minus b minus c minus pattern. This combination is what links the opposite spin sublattices only through those nonsymmorphic operations.

Lev: And that means they're not linked by simple translation or inversion symmetry, which is how they get that d-wave spin splitting without needing spin-orbit coupling at all.

Kai: That's a key part—

Conclusion: Kai: So, to wrap up, we’re talking about how interfacial charge transfer and octahedral tilts in these LaVO3/LaNiO3 superlattices create this emergent altermagnetism.

Mira: Yeah, so they found that this isn't just a passive effect; the charge transfer actually drives the system into a specific magnetic configuration.

Lev: From an error-correction standpoint, if you try to run this on real hardware, you gotta account for how much that charge transfer modifies the local moments on those Ni sites.

Kai: It turns what we thought were just paramagnetic nickelate layers into something magnetically active because of that charge transfer effect.

Mira: That active sublattice then settles into a C-type antiferromagnetic order combined with specific octahedral rotations.

Lev: Those rotations, like the a minus b plus c minus pattern, are what link the opposite spin sublattices only through those specific nonsymmorphic operations.

Kai: So they're not linked by simple symmetry operations, which is how they manage to get that d-wave spin splitting without needing spin-orbit coupling.

Mira: And the results show this non-relativistic splitting can reach about one hundred eighteen millielectron volts in the insulating superlattice case, which is about twice what you’d expect from bulk LaVO3.

Lev: That’s a big number to handle on real qubits; we have to make sure that this splitting doesn't introduce too much decoherence when we try to implement it.

Kai: The main implication for me is that interfacial charge transfer is a way to engineer magnetism in oxide heterostructures, which opens up new design principles.

Mira: Exactly, so it’s not just about finding new bulk candidates; it’s about tuning the interface itself to activate nonmagnetic parts like LaNiO3.

Lev: It means we should look at these interfaces as active components rather than just passive barriers when designing next-generation materials for quantum devices.

Kai: So, this suggests that manipulating the chemistry and structure right at the interface is a real knob we can use to control magnetism in these complex oxides.

Departamento de Física, Universidade Federal de Minas Gerais · Instituto de Física, Universidade de São Paulo

cond-mat.str-el, cond-mat.mtrl-sci

Submitted: 2026-10-21

Updated: 2026-10-21

License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/

Importance score: 83/100

The gist: The gist: Emergent altermagnetism emerges in (LaVO3)n/(LaNiO3)m superlattices from interfacial charge transfer and octahedral tilts.

Key concepts

Altermagnetism: A specific type of magnetic order where opposite-spin sublattices are linked only through non-symmetric operations. In this system, it arises from the interplay between charge transfer and structural tilts, resulting in a d-wave spin splitting without needing spin-orbit coupling.
Interfacial Charge Transfer: The movement of electrons across the boundary between LaVO3 and LaNiO3 layers. This transfer is driven by an oxygen band mismatch, leading to a shift in the valence states from V$^{4+}$ to V$^{4+}$ and Ni$^{2+}$, which fundamentally changes the magnetic character of the nickelate layer.
Octahedral Tilts: Rotations or distortions in the oxygen octahedra within the crystal structure. These tilts play a dual role: they stabilize local magnetic moments that select a C-type antiferromagnetic order, and they remove translational symmetries that would otherwise connect opposite spins, preserving the altermagnetic classification.

Terminology

Altermagnetism — 1× in this paper · explained in 4 episodes

Summary

The gist: Emergent altermagnetism emerges in (LaVO3)n/(LaNiO3)m superlattices from interfacial charge transfer and octahedral tilts.

How it works

The emergence of altermagnetism is driven by the interplay between interfacial charge transfer and octahedral tilts in (LaVO3)n/(LaNiO3)m superlattices, leading to a C-type antiferromagnetic order combined with specific octahedral rotations that link opposite-spin sublattices only through nonsymmorphic operations, yielding a d-wave spin splitting without spin-orbit coupling The charge transfer drives the system towards the V4+ and Ni2+ configuration, turning the otherwise paramagnetic nickelate layers into a magnetically active sublattice

Key Findings on Mechanism

The mechanism stabilizing the C-AFM ground state is a cooperative interplay between charge transfer and symmetry The oxygen-continuity band mismatch of approximately 0.64 eV acts as the main driving force for spontaneous and directional charge transfer, indicating that electrons are transferred from the V-3d orbitals to hybridized Ni-3d - O-2p states This charge transfer quenches oxygen ligand holes and establishes the emergent V4+ (3d1) and Ni2+ (3d8) like configurations

Symmetry and Magnetic Order

The structural analysis reveals that the oxygen octahedra in (LVO)1/(LNO)1, (LVO)2/(LNO)2, and (LVO)2/(LNO)4 superlattices are characterized by octahedral rotations denoted as a −b+c−, a −b+c−, and a −b−c− patterns, respectively The resulting C-AFM order is the ground state for (LVO)1/(LNO)1 and (LVO)2/(LNO)2, and (LVO)2/(LNO)4 SLs The nonsymmorphic operations, specifically a twofold screw axis along c and a glide plane perpendicular to c with intrinsic translation a/2, connect the opposite spin sublattices without any translation or inversion, indicating that the altermagnetic classification (d-wave type) is preserved

Spin Splitting Characteristics

The resulting non-relativistic spin splitting reaches up to 117.9 meV in the insulating (LVO)1/(LNO)1 superlattice in the absence of SOC, which is about twice that calculated for bulk LaVO3 Orbital-resolved band structures show that both the vanadium and nickel sublattices host the splitting, establishing the observed altermagnetism as a collective, charge transfer driven phase distinct from a passive proximity effect The momentum-dependent spin splittings are characterized by a mixed d-wave form factor, where 27%, 28%, and 45% of the splitting weight resides on the oxygen states

Design Principle

The findings identify interfacial charge transfer as a design principle for engineering altermagnetic phases in oxide superlattices This route is complementary to the search for intrinsic bulk candidates, by activating otherwise nonmagnetic constituents such as LaNiO3 The confinement of (LVO)1/(LNO)1 drives the system into an insulating regime within DFT+U, with an indirect band gap of 1.62 eV The interfacial charge transfer fills the ligand holes, and the resulting Ni cations are fundamentally reconfigured to be in an active, 3d8 state

Conclusion

The paper demonstrates that interfacial charge transfer in (LaVO3)n/(LaNiO3)m superlattices turns the paramagnetic metallic LaNiO3 layers into a magnetically active Ni2+ (3d8) sublattice that participates in an altermagnetic emergent phase The resulting spin-splitting is fixed by the nonsymmorphic spin-group symmetries, which are insensitive to such effects This route is complementary to the search for intrinsic bulk candidates. The authors stress that this route is complementary to the search for intrinsic bulk candidates.

How it works

The octahedral tilts play a dual role, narrowing the bands and stabilizing the local moments whose superexchange selects the C-AFM order, while also removing lattice translation symmetries that connect the two spin sublattices in the untilted structure The absence of these distortions restores translational symmetries connecting the sublattices and completely suppressing the momentum-dependent nonrelativistic spin splitting observed in the distorted P21/c phase.

Charge transfer and Magnetic Moments

The layer resolved charge transfer and magnetic moments exhibit a spatial reduction away from the interface, showing that transferred electrons from vanadate layers are screened within approximately one unit cell of the interface The interfacial Ni sites exhibit enhanced magnetic moments, while the inner Ni sites show a reduction in local magnetic moments This spatial accommodation and local electronegativity equalization is further corroborated by the continuous spatial profile of the effective charge-transfer energy (ϵdp) across the superlattice

Structural Evolution

The structural signature of this interfacial charge transfer is confirmed by the evolution of local octahedral volumes, where VO6 octahedra undergo a volumetric contraction relative to bulk values, consistent with a V3+ to V4+ valence shift This volume variation provides a structural signature of the interfacial charge transfer The spatial gradient indicates that the charge transfer is screened within a few unit cells

Electronic Structure

The spin-resolved electronic band structure demonstrates the existence of momentum-dependent spin splittings, with the maximum splitting reaching approximately 100 meV in the fully confined limit superlattice being comparable to giant Rashba splittings of polar semiconductors The confinement of LVO within (LVO)1/(LNO)1 enhances the altermagnetic spin splitting for bands around the edges, which is a consequence of the confinement at the interface and maximization of out-of-plane VO-Ni apical angles The calculated non-relativistic splitting on (a) is comparable to the giant Rashba splittings of polar semiconductors such as the BiTeI

Orbital Origin

The leading tV-O and tNi-O hopping amplitudes are around 1.9 and 1.35 eV, which exceed the direct tV-V and tNi-Ni hoppings by an order of magnitude The eigenstates near the splitting maxima are strongly mixed V t2g/Ni eg - O-2p states The O-2p states therefore actively co-carry the momentum dependent spin splitting through covalent mixing with the magnetic d orbitals, rather than merely mediating the superexchange between them The contribution to the spin splitting is nearly half from oxygen states, showing that the altermagnetism in (LVO)1/(LNO)1 is not a purely d − d phenomenon but a ligand-assisted one

Summary of Results

In summary, interfacial charge transfer in (LaVO3)n/(LaNiO3)m superlattices turns the paramagnetic metallic LaNiO3 layers into a magnetically active Ni2+ (3d8) sublattice that participates in an altermagnetic emergent phase The resulting spin-splitting of ≈ 118 meV is about twice that of bulk LaVO3, and it decreases as the nickelate layers become thicker and recover their bulk-like character The mechanism is a cooperative interplay between charge transfer and symmetry The charge transfer drives the system into a Ctype AFM order, stabilizing a V4+ (3d1) and Ni2+ (3d8) like configurations

Conclusion

The authors identify interfacial charge transfer in correlated oxide heterostructures as a design principle (tuning knob) for engineering and enhancing altermagnetism, by activating otherwise nonmagnetic constituents such as LaNiO3. The authors stress that this route is complementary to the search for intrinsic bulk candidates.

Acknowledgments

The authors acknowledge the financial support from the Air Force Office of Scientific Research (grant number FA9550-24-1-0279) W. H. B. also acknowledges the financial support from the Brazilian agency CNPq (Grants 201149/2024-9, and 305726/2023-4) W. H. B. thank M. Radovic, T. Schmitt, and C. Piamonteze for useful discussions The authors acknowledge the National Laboratory for Scientific Computing (LNCC/MCTI, Brazil) for providing HPC resources of the SDumont supercomputer (URL: http://sdumont.lncc.br), which have contributed to the research results reported within this paper.

References

[1] M. Imada, A. Fujimori, and Y.

Improvements for AI systems

System design for oxide heterostructures can be guided by interfacial charge transfer, which acts as a design principle for engineering altermagnetism in oxide heterostructures. This allows AI systems to predict emergent magnetic phases based on predicted chemical interfaces rather than relying solely on bulk material properties.
Prediction of magnetic ground states in superlattices can incorporate structural symmetry analysis, specifically identifying the nonsymmorphic screw and glide operations that link opposite spin sublattices, which is crucial for understanding the d-wave spin splitting without spin-orbit coupling.
AI systems can model the role of octahedral tilts by recognizing that they play a dual role, narrowing bands to stabilize local moments while simultaneously removing lattice translation symmetries that connect sublattices in untilted structures.
Prediction of electronic properties, such as momentum-resolved spin splittings, can be performed using Wannier band manifold analysis and Taylor expansion constrained by magnetic space group symmetries to extract the d-wave type form factor coefficients like alpha and beta.
AI can predict the orbital origin of spin splitting by analyzing which orbitals contribute most to the splitting weight, such as finding that nearly half of the splitting weight thus resides on the oxygen states due to strong p-d covalency in (LVO)1/(LNO)1 SLs.