Fig. 1
From: Topological superconducting phase in high-Tc superconductor MgB2 with Dirac–nodal-line fermions
Crystal and electronic structure of MgB2. a Crystal structure of MgB2 with P6/mmm symmetry. b Bulk BZ and the projected BZ of the (010) and (001) surface with purple lines indicating the locations of cuts 1–4 for surface states in Fig. 2a. c π (B pz) and σ (B s, px,y) bonding character of boron sheet. d Band structure of MgB2 with the coded bonding character. The color gradient from purple to blue represents a varying contribution from σ bonding to π bonding of boron sheet. e Band structure along high-symmetry points which are located in the same plane as varying the kz value. f Dispersive Dirac nodal line structure along the K–H direction as indicated by a small cyan rectangle in b
