Ab initio calculations of Fano interference in multi-Weyl semimetals

• Grant number: 24/20767-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: September 01, 2025
• End date: August 31, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - Condensed Matter Physics
• Principal Investigator: Antonio Carlos Ferreira Seridonio
• Grantee: Gabriel Menegolo de Castro Meira
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil

Abstract

This project aims to investigate the Fano interference in multi-Weyl semimetals, beginning with the triple-Weyl case ($J=3$), followed by double ($J=2$) and single ($J=1$) cases, where $J$ denotes the topological charge. According to Phys. Rev. B105, 235135 (2022) [1], in the low-energy approximation (effective model), the Fano parameter $q_{J}$ is determined by the angle of the corresponding rotational symmetry group $C_{2J}$ of the crystal, specifically for $J=3$. Notably, $q_{J}$ quantifies the interference in the local density of states (LDOS) induced by an impurity, defined as the ratio of the real and imaginary parts of the pristine system's retarded Green's Function (GF) [1]. Multi-Weyl semimetals exist if $C_{2J}$ satisfies the condition $J\leq3$ according to Phys. Rev. Lett.108, 266802 (2012) [2]. However, due to the limitations of the approximation in [1], the relationship between $q_{J}$ and $C_{2J}$ has not been established for $J=2$ and $J=1$. Understanding $q_{J}$ is essential for determining the topological charge via quantum transport analyses, as shown in [1]; from the Fano spectral line, one can extract $q_{J}$ and, through its relationship with $J$, identify the topological charge value. To overcome the limitations of the effective model, we will implement ab initio calculations based on Density Functional Theory (DFT) to determine the GF. These DFT calculations will be complemented by the Kramers-Kronig transformation, as standard DFT analysis provides the LDOS (proportional to the imaginary part of the GF), and the transformation yields the real part of the GF from the imaginary part. A parallel approach using wannierization will also be conducted. In this way, we will revisit the $J=3$ case from [1] and extend the study to cases with $J=2$ and $J=1$. The methodology will utilize the quantum espresso, wannier90 and wanniertools packages. (AU)