PY-Nodes: An ab-initio python code for searching nodes in a material using Nelder-Mead's simplex approach

Pandey, Vivek; Pandey, Sudhir K.

doi:10.48550/arxiv.2202.02251

Cited by 1 publication

(1 citation statement)

References 37 publications

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“…We do this by applying an iterative Nelder Mead minimization algorithm to a grid of initial points in the BZ as proposed in Ref. [151]. In Fig.…”

Section: D Spinful Time-reversal Invariant Systems With Inversion Sym...mentioning

confidence: 99%

Spin-Resolved Topology and Partial Axion Angles in Three-Dimensional Insulators

Lin¹,

Palumbo²,

Guo³

et al. 2022

Preprint

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Topological insulating (TI) phases were originally highlighted for their disorder-robust bulk responses, such as the quantized Hall conductivity of 2D Chern insulators. With the discovery of time-reversal-(T -) invariant 2D TIs, and the recognition that their spin Hall conductivity is generically non-quantized, focus has since shifted to boundary states as signatures of 2D and 3D TIs and symmetry-enforced topological crystalline insulators (TCIs). However, in T -invariant (helical) 3D TCIs such as bismuth, BiBr, and MoTe2 -termed higher-order TCIs (HOTIs) -the boundary signatures manifest as 1D hinge states, whose configurations are dependent on sample details. It is hence desirable to elucidate bulk signatures of helical TCIs, and their relationship to sample-independent experimental observables. In this work, we introduce nested spin-resolved Wilson loops and layer constructions as tools to characterize the bulk topological properties of Iand T -protected helical HOTIs. We discover that helical HOTIs realize one of three spin-resolved phases with distinct responses that are quantitatively robust to large deformations of the bulk spin-orbital texture: 3D quantum spin Hall insulators (QSHIs), "spin-Weyl" semimetal states with gapless spin spectra, and T -doubled axion insulator (T-DAXI) states with nontrivial partial axion angles θ ± = π indicative of a 3D spin-magnetoelectric bulk response. We provide experimental signatures of each spin-stable regime of helical HOTIs, including surface Fermi arcs in spin-Weyl semimetals under strong Zeeman fields, and half-quantized 2D TI states on the gapped surfaces of T-DAXIs originating from a partial parity anomaly. Lastly, we use ab-initio calculations to demonstrate that the candidate HOTI β-MoTe2 realizes a spin-Weyl state with 8 total spin-Weyl points.

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“…We do this by applying an iterative Nelder Mead minimization algorithm to a grid of initial points in the BZ as proposed in Ref. [151]. In Fig.…”

Section: D Spinful Time-reversal Invariant Systems With Inversion Sym...mentioning

confidence: 99%