Twelve inequivalent Dirac cones in two-dimensional ZrB2

Abstract

Theoretical evidence of the existence of 12 inequivalent Dirac cones at the vicinity of the Fermi energy in monolayered ZrB2 is presented. Two-dimensional ZrB2 is a mechanically stable d-and porbital compound exhibiting a unique electronic structure with two Dirac cones out of high-symmetry points in the irreducible Brillouin zone with a small electron-pocket compensation. First-principles calculations demonstrate that while one of the cones is insensitive to lattice expansion, the second cone vanishes for small perturbation of the vertical Zr position. Internal symmetry breaking with external physical stimuli, along with the relativistic effect of SOC, is able to remove selectively the Dirac cones. A rational explanation in terms of d-and p-orbital mixing is provided to elucidate the origin of the infrequent amount of Dirac cones in a flat structure. The versatility of transition metal d-orbitals combined with the honeycomb lattice provided by the B atoms yields novel features never observed in a two-dimensional material.

Negative differential conductance effect and electrical anisotropy of 2D ZrB2 monolayers

“…[26]. The band structures of its hexagonal unit cell is shown in figure S1, also in consistent with results in the literature [12].…”

“…The same NDC mechanism is also applicable to the a-ZrB2, and its bias-dependent transmission spectra and electrode bands are given in figure S3. With a high bias (such as 2.0 V), a 12 large gap is appeared in the band overlap of the left and right electrodes (see figure S3 (c)). It results a transmission gap at the corresponding energy region (from 0.05 to 0.25 eV) and depressed I−V curve compared to the z-ZrB2.…”

Unveiling the Electric-Current-Limiting and Photodetection Effect in Two-Dimensional Hydrogenated Borophene

“…Recently, borophene and its derivatives have received increasing attention since its successful realization in 2015 [1,2]. Many different types of borophene-based monolayer (ML) [3][4][5][6] structures have been proposed in theory, and they are promising for a variety of applications [7], including Dirac materials [8], lithium-sulfur batteries [9], spin-filters [10], superconducting materials [11], hydrogen storage media [12], and catalysts [13]. The borophene MLs such as the out-of-plane buckling sheets [1] and β12 and χ3 boron sheets [2] are often fabricated on metal (Ag) substrates, as a truly free-standing two-dimensional (2D) borophene is unstable according to theoretical studies [14,15].…”

“…Recently, borophene and its derivatives have received increasing attention since its successful realization in 2015 [1,2]. Many different types of borophene-based monolayer (ML) [3][4][5][6] structures have been proposed in theory, and they are promising for a variety of applications [7], including Dirac materials [8], lithium-sulfur batteries [9], spin-filters [10],…”

f-Orbital based Dirac states in a two-dimensional uranium compound

“…In monolayered UB 4 a triangular network of U atoms is sandwiched between two B honeycombed lattices (see figures 1(a) and (b)), so each U atom is connected by covalent bonds with twelve B atoms. The optimized lattice parameter is 3.11 Å, and the separation between parallel B layers is 3.65 Å. Nanostructures with similar geometry and based on boron and dorbital transition metal atoms were studied previously [25,26].…”