Adrien Bouhon

Current inversion at the edges of a chiral p-wave superconductor

Motivated by Sr2RuO4, edge quasiparticle states are analyzed based on the self-consistent solution of the Bogolyubov-de Gennes equations for a topological chiral p-wave superconductor. Using a tight-binding model of a square lattice for the dominant gamma band, we explore the nontrivial geometry and band structure dependence of the edge states and currents. As a peculiar finding, we show that, for high band fillings, currents flow in a reversed direction when comparing straight and zigzag edges. We give a simple explanation in terms of the positions of the zero-energy bound states using a quasiclassical picture. We also show that a Ginzburg-Landau approach can reproduce these results. Moreover, the band filling dependence of the most stable domain wall structure is discussed.

Global band topology of simple and double Dirac-point semimetals

We combine space group representation theory together with the scanning of closed subdomains of the Brillouin zone with Wilson loops to algebraically determine the global band-structure topology. C ...

Three-dimensional organic Dirac-line materials due to nonsymmorphic symmetry : A data mining approach

A datamining study of electronic Kohn-Sham band structures was performed to identify Dirac materials within the Organic Materials Database. Out of that, the three-dimensional organic crystal 5,6-bi ...

Data Mining for Three-Dimensional Organic Dirac Materials : Focus on Space Group 19

We combined the group theory and data mining approach within the Organic Materials Database that leads to the prediction of stable Dirac-point nodes within the electronic band structure of three-dimensional organic crystals. We find a particular space group P212121 (#19) that is conducive to the Dirac nodes formation. We prove that nodes are a consequence of the orthorhombic crystal structure. Within the electronic band structure, two different kinds of nodes can be distinguished: 8-fold degenerate Dirac nodes protected by the crystalline symmetry and 4-fold degenerate Dirac nodes protected by band topology. Mining the Organic Materials Database, we present band structure calculations and symmetry analysis for 6 previously synthesized organic materials. In all these materials, the Dirac nodes are well separated within the energy and located near the Fermi surface, which opens up a possibility for their direct experimental observation.

Influence of the domain walls on the Josephson effect in Sr2RuO4

A detailed theoretical interpretation of the Josephson interference experiment between Sr2RuO4 and Pb reported by Kidwingira et al (2006 Science 314 1267) is given. Assuming chiral p-wave pairing symmetry, a Ginzburg–Landau theory is derived in order to investigate the structure of domain walls between chiral domains. It turns out that anisotropy effects of the Fermi surface and the orientation of the domain walls are essential for their internal structure. Introducing a simple model for a Josephson junction, the effect of domain walls intersecting the interface between Sr2RuO4 and Pb is discussed. It is shown that characteristic deviations of the Fraunhofer interference pattern for the critical Josephson current as a function of the magnetic field occurs in qualitative agreement with the experimental finding. Moreover, the model is also able to account for peculiar hysteresis effects observed in the experiment.

From chiral d-wave to nodal line superconductivity in the harmonic honeycomb lattices

Motivated by the recent realization of the three-dimensional hyperhoneycomb and stripyhoneycomb lattices in lithium iridate (Li2IrO3), we study the possible spin-singlet superconducting states on t ...

Domain walls in a chiral d -wave superconductor on the honeycomb lattice

We perform a fully self-consistent study of domain walls between different chiral domains in chiral

Gap opening and large spin–orbit splitting in (M = Mo,W; X = S,Se,Te) from the interplay between crystal field and hybridisations: insights from ab-initio theory

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Bulk topology of line-nodal structures protected by space group symmetries in class AI

-wave superconductors with an underlying honeycomb lattice structure. We investigate domain walls along all possible armchair and zigzag directions and with a finite global phase shift across the domain wall, in addition to the change of chirality. For armchair domain walls we find the lowest domain wall energy at zero global phase shift, while the most favorable zigzag domain wall has a finite global phase shift dependent on the doping level. Below the van Hove singularity the armchair domain wall is most favorable, while at even higher doping the zigzag domain wall has the lowest energy. The domain wall causes a local suppression of the superconducting order parameter, with the superconducting recovery length following a universal curve for all domain walls. Moreover, we always find four subgap states crossing zero energy and well localized to the domain wall. However, the details of their energy spectrum vary notably, especially with the global phase shift across the domain wall.

Wilson loop approach to metastable topology of split elementary band representations and topological crystalline insulators with time reversal symmetry.

Abstract By means of first-principles density functional calculations, we study the maximally localised Wannier functions for the 2D transition metal dichalcogenides (M = Mo,W; X = S,Se,Te). We have found that part of the energy gap is opened by the crystal field splitting induced by the -like atoms. The inversion of the band character between the and the K points of the Brillouin zone is due to the M–M hybridisation. The consequence of this inversion is the closure of the gap in absence of the M–X hybridisation. The M–X hybridisation is the only one that tends to open the gap at every k-point. It is found that the change in the M–X and M–M hybridisation is the main responsible for the difference in the gap between the different dichalcogenide materials. The inversion of the bands gives rise to different spin–orbit splitting at and K point in the valence band. The different character of the gap at and K point offers the chance to manipulate the semiconducting properties of these compounds. For a bilayer system, the hybridisation between the out-of-plane orbitals and the hybridisation between the in-plane orbitals split the valence band respectively at the and K point. The splitting in the valence band is opened also without spin–orbit coupling and occurs due to the M–M and X–X hybridisation between the two monolayers. The transition from direct to indirect band gap is governed by the hybridisation between out-of-plane orbitals of different layers and in-plane orbitals of different layers.