Majorana vortex phases in time-reversal invariant higher-order topological insulators and topologically trivial insulators
Pith reviewed 2026-05-22 13:05 UTC · model grok-4.3
The pith
Majorana vortex end modes persist in time-reversal invariant systems with fully gapped surfaces even when topologically trivial.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
Z2-protected Majorana vortex end modes emerge when the chemical potential lies between the critical chemical potentials of the two component TI vortex transitions. These modes remain present even when all surfaces are gapped with the same sign, rendering the system topologically trivial in both first- and second-order classifications.
What carries the argument
Double TI construction with time-reversal symmetry preserving mass terms that anisotropically gap the surface states.
Load-bearing premise
The mass terms that anisotropically gap the surface states of the double TI have a negligible impact on the vortex phase transitions and induce no additional topological phase transitions.
What would settle it
Varying the magnitude of the surface-gapping mass terms and observing whether the chemical-potential window supporting MVEMs stays fixed or acquires new phase boundaries.
Figures
read the original abstract
Majorana vortex phases have been extensively studied in topological materials with conventional superconducting pairing. Inspired by recent experimental progress in realizing time-reversal invariant higher-order topological insulators (THOTIs) and inducing superconducting proximity effects, we investigate Majorana vortex phases in these systems. We construct THOTIs as two copies of a topological insulator (TI) with time-reversal symmetry-preserving mass terms that anisotropically gap the surface states. We find that these mass terms have a negligible impact on the vortex phase transitions of double TIs when treated as perturbations, and no additional topological phase transitions are induced. Consequently, $\mathbb{Z}_2$-protected Majorana vortex end modes (MVEMs) emerge when the chemical potential lies between the critical chemical potentials $\mu_c^{(1)}$ and $\mu_c^{(2)}$ of the two TI vortex phase transitions. We demonstrate this behavior across multiple THOTI models, including rotational symmetry-protected THOTI, inversion symmetry-protected THOTI, rotational and inversion symmetries-protected THOTI bismuth, and extrinsic THOTI. Remarkably, MVEMs persist even when all surfaces are gapped with the same sign, rendering the system topologically trivial in both first- and second-order classifications. Our findings establish that MVEMs can be realized in time-reversal invariant systems with fully gapped surfaces, encompassing both topologically nontrivial and trivial insulators, thus significantly broadening the solid state material platforms for hosting Majorana vortex phases.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims that Z2-protected Majorana vortex end modes (MVEMs) persist in time-reversal invariant higher-order topological insulators (THOTIs) constructed as double TIs plus TRS-preserving mass terms, as well as in topologically trivial insulators. Explicit lattice models are built for rotational, inversion, bismuth-type, and extrinsic cases; the mass terms are treated as perturbations that anisotropically gap surfaces but leave the vortex critical chemical potentials μ_c^(1) and μ_c^(2) essentially unchanged, with no additional transitions. Consequently MVEMs appear in the window between those critical points even when all surfaces are gapped with uniform sign, rendering the system trivial in both first- and second-order classifications.
Significance. If the results hold, the work substantially broadens candidate platforms for Majorana vortex phases to include fully gapped, time-reversal invariant systems that are trivial in both first- and second-order topology. Credit is due for the concrete lattice Hamiltonians, phase diagrams, and mode spectra supplied for multiple symmetry classes; these constitute explicit, reproducible constructions that directly illustrate the claimed persistence of MVEMs.
minor comments (3)
- [§3] §3 (model Hamiltonians): the statement that the mass terms induce 'no additional topological phase transitions' would benefit from an explicit statement of the criterion used to detect transitions (e.g., closing of the bulk gap or change in the Z2 invariant of the vortex sector).
- [Figure 4] Figure 4 (phase diagrams): axis labels and color scales should be repeated on all panels for immediate readability when comparing the double-TI and mass-gapped cases.
- [Conclusion] The abstract and introduction cite the persistence of MVEMs in the trivial regime; a brief sentence in the conclusion summarizing the range of chemical potentials over which this holds for each model would improve clarity.
Simulated Author's Rebuttal
We thank the referee for the positive evaluation of our manuscript and the recommendation for minor revision. The referee's summary accurately captures the central claims and constructions presented in the work.
Circularity Check
No significant circularity; derivation relies on explicit model constructions
full rationale
The paper builds concrete lattice Hamiltonians for rotational, inversion, and bismuth-type THOTIs plus the trivial insulator case. It treats the anisotropic surface-gapping mass terms as perturbations and reports (via phase diagrams and mode spectra) that vortex critical points μ_c^(1) and μ_c^(2) remain essentially unchanged with no extra transitions. The persistence of Z2-protected MVEMs in the window between those points, even when all surfaces are gapped with uniform sign, follows directly from these model calculations rather than from any quantity defined in terms of itself, any fitted parameter renamed as a prediction, or any load-bearing self-citation chain. The derivation is therefore self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
axioms (2)
- domain assumption Time-reversal symmetry is preserved by the added surface mass terms.
- domain assumption The superconducting pairing is conventional and proximity-induced.
Lean theorems connected to this paper
-
IndisputableMonolith/Foundation/AbsoluteFloorClosure.leanreality_from_one_distinction unclear?
unclearRelation between the paper passage and the cited Recognition theorem.
We construct THOTIs as two copies of a topological insulator (TI) with time-reversal symmetry-preserving mass terms that anisotropically gap the surface states... MVEMs persist even when all surfaces are gapped with the same sign, rendering the system topologically trivial in both first- and second-order classifications.
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
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