Chiral magnetic conductivity and surface states of Weyl semimetals in topological insulator ultra-thin film multilayer

TL;DR

This paper models 3D Weyl semimetals using topological insulator multilayers and organic materials, analyzing their topological phases, surface states, and chiral magnetic effects through theoretical and lattice models.

Contribution

It introduces a new multilayer model for 3D Weyl semimetals, studies their topological phases and surface states, and connects organic material models to topological insulator systems.

Findings

Identification of topological phase transitions via tunneling parameters

Calculation of chiral magnetic conductivity showing phase-dependent plateaus

Surface states and Fermi arcs consistent with Weyl semimetal topology

Abstract

We investigate an ultra-thin film of topological insulator (TI) multilayer as a model for a three-dimensional (3D) Weyl semimetal. We introduce tunneling parameters $t_S$, $t_\perp$, and $t_D$, where the former two parameters couple layers of the same thin film at small and large momenta, and the latter parameter couples neighbouring thin film layers along the $z$-direction. The Chern number is computed in each topological phase of the system and we find that for $t_S,t_D>0$, the tunneling parameter $t_\perp$ changes from positive to negative as the system transits from Weyl semi-metallic phase to insulating phases. We further study the chiral magnetic effect (CME) of the system in the presence of a time dependent magnetic field. We compute the low-temperature dependence of the chiral magnetic conductivity and show that it captures three distinct phases of the system separated by plateaus. Furthermore, we propose and study a 3D lattice model of Porphyrin thin film, an organic material known to support topological Frenkel exciton edge states. We show that this model exhibits a 3D Weyl semi-metallic phase and also supports a 2D Weyl semi-metallic phase. We further show that this model recovers that of 3D Weyl semimetal in topological insulator thin film multilayer. Thus, paving the way for simulating a 3D Weyl semimetal in topological insulator thin film multilayer. We obtain the surface states (Fermi arcs) in the 3D model and the chiral edge states in the 2D model and analyze their topological properties.