Moving Dirac nodes by chemical substitution

Abstract

Dirac fermions play a central role in the study of topological phases, for they can generate a variety of exotic states, such as Weyl semimetals and topological insulators. The control and manipulation of Dirac fermions constitute a fundamental step toward the realization of novel concepts of electronic devices and quantum computation. By means of Angle-Resolved Photo-Emission Spectroscopy (ARPES) experiments and ab initio simulations, here, we show that Dirac states can be effectively tuned by doping a transition metal sulfide, BaNiS2, through Co/Ni substitution. The symmetry and chemical characteristics of this material, combined with the modification of the charge-transfer gap of BaCo1−xNixS2 across its phase diagram, lead to the formation of Dirac lines, whose position in k-space can be displaced along the Γ−M symmetry direction and their form reshaped. Not only does the doping x tailor the location and shape of the Dirac bands, but it also controls the metal-insulator transition in the same compound, making BaCo1−xNixS2 a model system to functionalize Dirac materials by varying the strength of electron correlations.

Dichroism in time-resolved ARPES and valence band orbital nature in BaNiS2

“…We can see that there were strong CD in B bands around Γ point and Dirac cone. Even though the formation mechanism of Dirac cone in BaNiS 2 is different from topological insulators [5], it shows a similar CD pattern compared to well-known topological insulators like Bi 2 Se 3 [23,24]. In Fig.…”

“…As underlined by recent studies [4][5][6], the most important electronic properties of BaNiS 2 are related to the Dirac cones and to the electron pocket at Γ. We consequently focused on these bands when exploring in detail the polarization dependence of the whole angular photoemission yield, by using the ARTOF photoelectron detector of our ultrafast time-resolved ARPES setup.…”

“…This is consistent to what we observed in ref. [1,5]. Circular Dichroisms (CDs) of BaNiS 2 around Γ point and Dirac cone were investigated and plotted in Fig.…”

“…Furthermore, the presence of tunable quasi two-dimensional Dirac cones stemming from a nonsymmorphic symmetry of the lattice has been recently demonstrated [4]. It has been shown that the tunability of Dirac cones origins from the charge transfer generated by the hybridization between p and d orbitals [5], which makes BaNiS 2 a promising system to functionalize Dirac stats by manipulating the strength of electron correlations. Furthermore, BaNiS 2 is the metallic precursor of BaCo 1−x Ni x S 2 , which presents great similarities with high-Tc cuprates, but no superconductivity [6][7][8].…”

Photoinduced renormalization of Dirac states in BaNiS$_2$

“…We first focus on the ultrafast dynamics of each Dirac band by tuning the light polarization as described elsewhere [13,21]. Figs.…”