Threefold Fermions, Weyl Points, and Superconductivity in the Mirror Symmetry Lacking Semiconductor TlCd2Te4

Abstract

The topological phase transition and exotic quasiparticles in materials have attracted much attention because of their potential in spintronics and mimic of elementary particles. Especially, great research interest has been paid to search for the Weyl fermions in solid-state physics. By using first-principles calculations, we predict that the multinary semiconductor alloy TlCd2Te4 exhibits threefold fermions and nodal-line fermions, which are protected by the S4 improper rotational symmetry. Moreover, owing to the lack of inversion and mirror symmetries, the threefold fermions split into Weyl fermions when the spin-orbit coupling is included. The chiral charge of Weyl points and the Z2 time-reversal topological invariant are investigated. The topological surface states, spin texture, and electron-phonon coupling analysis are presented. Our study demonstrates TlCd2Te4 as a good platform to understand topological phase transitions as well as possible coexistance of topological Weyl semimetal and superconductivity in one single material.

Advances in Topological Materials: Fundamentals, Challenges and Outlook

“…This article presents the topological and nontopological phase transitions in In x Ga 1−x N/GaN and InN/In y Ga 1−y N double quantum wells and proposes a structure for which the bulk energy gap in the topological insulator state is the largest. The paper by Huang et al reports that TlCd 2 Te 4 alloys exhibit exotic states such as threefold fermions and nodal-line fermions which split into Weyl fermions when the spin-orbit coupling is included [6]. This work also reveals that electron-doped TlCd 2 Te 4 can become a superconductor at low temperatures, allowing for the coexistence of the topological Weyl semimetal and superconductivity in a single material.…”

“…This Special Issue, containing eight research works and one review, is an interesting collection of papers on topological materials. The papers present a variety of materials including conventional 3D topological insulators such as HgTe, Bi 2 Se 3 , and (Bi 1−x Sb x ) 2 Te 3 [1][2][3]; 3D antiferromagnetic topological insulator MnBi 2 Te 4 [4]; 2D topological insulator in InN/InGaN quantum wells [5]; Weyl semimetals [6,7]; Floquet second-order topological phases realized in cold atom systems [8]. One paper is devoted to the quantum phase transition in Co-based magnetic tunnel junctions [9].…”

“…One paper is devoted to the quantum phase transition in Co-based magnetic tunnel junctions [9]. The studies presented in [1][2][3][4] are experimental, while [5][6][7][8][9] are theoretical. Here, we provide a brief overview of the individual papers.…”