Title:	Defect- and Dopant-Engineered Quantum Centers and Band-Environment Control in Pb-Based 2D Halide Perovskites: A First-Principles Study
DNr:	NAISS 2026/3-207
Project Type:	NAISS Medium
Principal Investigator:	Roghayeh Imani <imani.roghayeh@gmail.com>
Affiliation:	Luleå tekniska universitet
Duration:	2026-04-01 – 2026-11-01
Classification:	10304
Homepage:	https://www.ltu.se/
Keywords:

Abstract

Pb-based 2-D halide perovskites combine strong spin–orbit coupling, dielectric confinement, and a structurally soft Pb–I lattice, creating a unique environment where point defects can generate deep, spatially localized electronic states inside the band gap. When these states are spectrally isolated from extended Bloch bands, they form a small many-body Hilbert subspace behaving as a quantum center—a defect-bound quantum system analogous to an artificial atom in a crystalline host. The states originate from defect-localized orbitals whose occupancy produces discrete spin–orbit–entangled multiplets governed by Coulomb interaction, spin–orbit coupling, and hybridization with surrounding bands. If hybridization with the host lattice is weak and the defect level remains separated from the band continuum, the resulting state can function as an addressable quantum degree of freedom. Pb-based 2D halide perovskites provide an especially favorable environment for such quantum centers. Compared with conventional hosts such as diamond or SiC, they combine strong intrinsic spin–orbit coupling from Pb, enhanced Coulomb interactions due to dielectric confinement, and tunable band environments enabled by chemical alloying and structural softness. These properties make them promising platforms for defect-based quantum emitters, qubits, and exciton–photon interfaces in 2D architectures. However, the microscopic conditions under which defects become stable quantum centers rather than shallow traps remain largely unexplored. This project therefore aims to establish a first-principles design framework for quantum centers in Pb-based 2D perovskites. The project will employ density-functional theory calculations using Quantum ESPRESSO, including spin–orbit coupling and large 2D supercells, to identify and engineer quantum centers in Pb-based layered perovskites. In the first stage, intrinsic and extrinsic defects will be introduced in large supercells of Pb-based 2D perovskites. Candidate defects include Pb and halide vacancies, compound vacancies, antisites, and substitutional dopants. For each configuration we will compute defect formation energies, charge-transition levels, spin–orbit–coupled electronic structures, and localization of defect states. The goal is to identify defect configurations that produce isolated in-gap states with strong localization, characteristic of quantum centers. In the second stage, aliovalent substitution and halide alloying will tune the electronic environment surrounding these centers. Substitutions such as Pb→Sn/Bi or I→Br/Cl will be used to examine how the Fermi level, internal electric fields, and defect charge states evolve with doping, identifying regimes where defect states remain stable and isolated. Finally, the project will study how spatial arrangements of defects and dopants influence localization versus band-like transport by analyzing spin–orbit–coupled band structures, effective masses, and real-space wavefunctions. The project will deliver a first-principles defect and doping phase diagram for Pb-based 2D halide perovskites, identifying configurations that host stable localized quantum states and defining the conditions under which these states remain isolated from the band continuum. These results will provide theoretical design principles for defect-engineered quantum functionality in layered perovskites, enabling scalable platforms for quantum emitters, qubits, and hybrid exciton–photon systems.