arXiv subjects

E. Marinho Jr.

Publications and source records attributed to E. Marinho Jr..

3 recordsLinked to original sources

arXiv2025

Impact of Broken Inversion Symmetry on Molecular States in multi-Weyl fermions

We study inversion-symmetry (IS) breaking in impurity dimers coupled to topological multi-Weyl systems in the low-energy dispersion domain. In the IS-preserved multi-Weyl semimetal phase, Hubbard bands split into symmetric and antisymmetric molecular-like subbands. Breaking IS induces a transition to a multi-Weyl metal, lifting the degeneracy of the Weyl node and closing the pseudogap. This causes opposite energy shifts: valence-band symmetric (antisymmetric) subbands red- (blue-) shift, reversing in the conduction band until a degeneracy point. Beyond this threshold, symmetric bands flatten near band cutoffs, whereas antisymmetric bands form quasi-zero energy modes asymptotically approaching -- yet never crossing -- the Fermi level. Crucially, identical molecular symmetries maintain nondegeneracy even as energy separation vanishes with stronger IS breaking. Our results demonstrate symmetry-selective mechanisms for topological molecular states in multi-Weyl systems.

cond-mat.mes-hall↗

arXiv2025

Spin-Exchange Induced Spillover on Poor Man's Majoranas in Minimal Kitaev Chains

The "Poor Man's Majoranas" (PMMs) [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection can "spill over" from one edge into another of the minimal Kitaev chain when perturbed electrostatically. As aftermath, this leads to a delocalized Majorana fermion (MF) at both the edges. Additionally, according to recent differential conductance measurements in a pair of superconducting and spinless quantum dots (QDs), such a PMM picture was brought to reality [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. Based on this scenario, we propose the spillover of the PMM when its QD is exchange coupled to a quantum spin $S$. We show that if this QD is perturbed by the exchange coupling $J$, solely the half $2S+1$ $(2S+2)$ of the fine structure stays explicit for a fermionic (bosonic) $S.$ Concurrently, the other half squeezes itself as the delocalized MF zero-mode. Particularly, turning-off the superconductivity the multiplicity $2S+1$ holds regardless the spin statistics. Meanwhile, the PMM spillover induced by $J$ becomes a statistics dependent effect. Hence, our findings contribute to the comprehension of spin-phenomena interplay with superconductivity in minimal Kitaev chains, offering insights for future quantum computing devices hosting PMMs.

cond-mat.mes-hall↗

arXiv2024

Squeezed state protection of fine structure in "Poor Man's Majorana" via quantum spin coupling

The "Poor Man's Majorana" [Phys. Rev. B 86, 134528 (2012)] devoid of topological protection has been theoretically predicted to rely on the minimal Kitaev chain. Afterward, a pair of superconducting and spinless quantum dots turned the proposal practicable and differential conductance pinpointed consistent fingerprints with such a scenario [Nature 614, 445 (2023) and Nature 630, 329 (2024)]. In this work, we propose a model wherein the "Poor Man's Majorana" presents protection when one of the dots is exchange coupled to a quantum spin. If this quantum dot is perturbed by tuning the exchange coupling, the well-known spill over-like behavior of this Majorana surprisingly remains unchanged, and solely half of the fine structure is unexpectedly viewed. As a matter of fact, the "Poor Man's Majorana" zero mode consists in squeezing of the other half at zero frequency, which imposes its pinning there and prevents the mixing of the mode with the explicit fine structure. We claim that if the supposed unavoidable split of the zero mode by the fine structure is unexpectedly absent, then the "Poor Man's Majorana" can be considered robust against the quantum spin. In this way, it becomes protected and the lack of topological protection paradigm of the "Poor Man's Majorana" has been revisited, pushing this seemingly well-established issue into a new direction.

cond-mat.mes-hall↗