Phosphorene confined systems in magnetic field, quantum transport, and superradiance in the quasi-flat band

TL;DR

This paper investigates the spectral, transport, and topological properties of electrons in confined phosphorene systems, revealing unique edge states, magnetic field effects, and superradiance phenomena using a tight-binding model and Landauer-Buttiker formalism.

Contribution

It provides a detailed analysis of topological edge states, Hofstadter spectrum, and superradiance effects in phosphorene, highlighting how lattice structure breaking influences electron-hole asymmetry and transport.

Findings

Topological edge states exhibit degeneracy and localization properties.

Magnetic field induces quantum Hall plateaus via chiral edge states.

Superradiance affects density of states and electron transmission in open systems.

Abstract

Spectral and transport properties of electrons in confined phosphorene systems are investigated in a five hopping parameter tight-binding model, using analytical and numerical techniques. The main emphasis is on the properties of the topological edge states accommodated by the quasi-flat band that characterizes the phosphorene energy spectrum. We show, in the particular case of phosphorene, how the breaking of the bipartite lattice structure gives rise to the electron-hole asymmetry of the energy spectrum. The properties of the topological edge states in the zig-zag nanoribbons are analyzed under different aspects: degeneracy, localization, extension in the Brillouin zone, dispersion of the quasi-flat band in magnetic field. The finite-size phosphorene plaquette exhibits a Hofstadter-type spectrum made up of two unequal butterflies separated by a gap, where a quasi-flat band composed of zig-zag edge states is located. The transport properties are investigated by simulating a four-lead Hall device (importantly, all leads are attached on the same zig-zag side), and using the Landauer-Buttiker formalism. We find out that the chiral edge states due to the magnetic field yield quantum Hall plateaus, but the topological edge states in the gap do not support the quantum Hall effect and prove a dissipative behavior. By calculating the complex eigenenergies of the non-Hermitian effective Hamiltonian that describes the open system (plaquette+leads), we prove the superradiance effect in the energy range of the quasi-flat band, with consequences for the density of states and electron transmission properties.