Dirac fermions and superconductivity in the two-dimensional transition metals MOH(M=Zr,Hf)

Abstract

Discovering new two-dimensional (2D) Dirac semimetals incorporating both superconductivity and the topological band structure provides a novel platform for realizing the intriguing applications of massless Dirac fermions and Majorana quasiparticles, ranging from high-speed quantum devices at the nanoscale to topological quantum computations. In this work, utilizing first-principles calculations and symmetry analysis, we introduce MOH (M= Zr, Hf) as a new topological Dirac superconductor with Dirac points close to a Fermi level which are connected with nearly flat edge states as a striking feature of topological semimetals. Our calculations show that ZrOH as a 2D Dirac semimetal can exhibit superconductivity and is a novel platform for studying the interplay between superconductivity and Dirac states in low-dimensional materials.

Nonsymmorphic P21/m‐MoTe2: Novel 2D Topological Materials

“…We can find that there are two Dirac cones on high-symmetry line Γ-Y and the edge states clearly can be seen. The edge states are similar to that of other 2D Dirac semimetallic materials when SOC is not considered, such as 1T'-WTe 2 , [10] TPH-graphene, [63] ZrOH, [64] and borophene. [65] The 3D energy bands show that Dirac cone only exists on Γ-Y and there is no Dirac cone along the path of Γ-X.…”

Topological phases in $α$-Li$_{\rm 3}$N-type crystal structure of light-element compounds

“…Such degeneracy along the high-symmetry path is similar to the case of Na 3 N bulk structure. Since the system preserves both the IS and TRS symmetries, a quantized Zak phase is expected for a path along the reciprocal lattice vector perpendicular to the BZ edge [18,43]. The Zak phase jumps by π at the nodal lines scientifically verifying the nontrivial character of the nodal lines.…”

“…Most topological materials transform into typical materials when the material dimensions are varied from bulk structure to a two-dimensional (2D) thin film. More excitingly, the 2D structure of Li 3 N (Li 2 N monolayer) hosts the topologically nontrivial electronic states and we find that type-II nodal loop can be realized in monolayer (thin-film) of Li 3 N. The nodal loop emerges from the crossing between two electron-like bands around the Γ point and the highly disperse and flat bands appear in the vicinity of the Fermi level providing the necessary condition for possible high superconducting transition temperature in Li 2 N monolayer [18]. It is worth mentioning that a robust pinhole-free-Li 3 N solid thin-film has been recently fabricated with an excellent performance in Li metal anodes [19].…”

Hydrogenation induced high-temperature superconductivity in two-dimensional W2C3

“…It was previously proposed that superconductivity mainly arises from the coupling of s electrons with phonons. 42,43 The s bonds are formed by the sp 3 -hybridization of C atoms with H and W atoms in W 2 C 3 H 2 . Although there is a small peak in the DOS of H around the Fermi level, the energy of the s bonds contributed by the C-H bond mainly decreases below À4 eV.…”

“…The research on 2D superconductors provides a broad platform for the study of novel and inherent properties such as quantum phase transition, 1,2 topological superconductivity, 3 Ising superconductivity, 4 charge density wave (CDW) 5 and so on. Based on the BCS theory, 6 the superconductors with high T c can usually be obtained by enhancing the DOS at E F and the EPC.…”