Abstract
Iron-based superconductors have been identified as a novel platform for realizing Majorana zero modes (MZMs) without heterostructures, due to their intrinsic topological properties and high-Tc superconductivity. In the two-dimensional limit, the FeTe1−xSex monolayer, a topological band inversion has recently been experimentally observed. Here, we propose to create MZMs by applying an in-plane magnetic field to the FeTe1−xSex monolayer and tuning the local chemical potential via electric gating. Owing to the anisotropic magnetic couplings on edges, an in-plane magnetic field drives the system into an intrinsic high-order topological superconductor phase with Majorana corner modes. Furthermore, MZMs can occur at the domain wall of chemical potentials at either one edge or certain type of tri-junction in the two-dimensional bulk. Our study not only reveals the FeTe1−xSex monolayer as a promising Majorana platform with scalability and electrical tunability and within reach of contemporary experimental capability, but also provides a general principle to search for realistic realization of high-order topological superconductivity.
Highlights
Within the nomenclature of condensed matter, a Majorana zero mode (MZM) is an anyonic quasi-particle excitation with non-Abelian statistics, which underpins the concept of topological quantum computations [2,3,4,5,6,7,8,9]
By studying the topological phase transition (TPT) at the one-dimensional (1D) edge and its dependence on the magnetic field direction, we demonstrate the existence of the MZMs at the corner of two perpendicular edges with the in-plane magnetic field parallel to one edge (Fig.1(b)), derived from a magnetic-anisotropy induced high-order topological superconductor phase, and the chemical potential domain wall (CPDW) along 1D edge (Fig.1(c))
We further reveal a 2D bulk TPT between the quantum spin Hall (QSH) state and a trivial insulator induced by electric gating in the Fe(Te,Se) monolayer, due to which the MZM can be trapped in a tri-junction (Fig.1(d))
Summary
Within the nomenclature of condensed matter, a Majorana zero mode (MZM) is an anyonic quasi-particle excitation with non-Abelian statistics, which underpins the concept of topological quantum computations [2,3,4,5,6,7,8,9]. It is desirable to find an intrinsic, robust, and controllable Majorana platform that is compatible with existing fabrication and patterning technologies To this end, recent theoretical predictions and the experimental verification of a TSC phase at the surface of Fe(Se,Te) SCs [32,33,34,35,36,37,38] provides an exciting opportunity due to their intrinsic nature of both superconductivity and non-trivial band structure which further comes along with a comparably high critical temperature Tc. More recently, the direct observation of band inversion in two-dimensional (2D) Fe(Se,Te) monolayer suggests the coexistence of a quantum spin Hall (QSH) state and superconductivity, providing a new two-dimensional (2D) platform for MZMs [1, 39], with a Tc of 40 K [40] and a large in-plane upper critical field of about 45 T[41]. We find an SC gap at Γ for helical edge states at zero magnetic field (Fig. 2 (a)).
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