2019 journal article

Many-Body Quantum Monte Carlo Study of 2D Materials: Cohesion and Band Gap in Single-Layer Phosphorene

PHYSICAL REVIEW X, 9(1).

By: T. Frank*, R. Derian*, K. Tokar*, L. Mitas n, J. Fabian* & I. Stich*

co-author countries: Germany 🇩🇪 Slovakia 🇸🇰 United States of America 🇺🇸
Source: Web Of Science
Added: February 11, 2019

The quantum Monte Carlo (QMC) method is applied to obtain the fundamental (quasiparticle) electronic band gap Δf of a semiconducting two-dimensional phosphorene whose optical and electronic properties fill the void between graphene and 2D transition-metal dichalcogenides. Similarly to other 2D materials, the electronic structure of phosphorene is strongly influenced by reduced screening, making it challenging to obtain reliable predictions by single-particle density-functional methods. Advanced GW techniques, which include many-body effects as perturbative corrections, are hardly consistent with each other, predicting the band gap of phosphorene with a spread of almost 1 eV, from 1.6 to 2.4 eV. Our QMC results, from infinite periodic superlattices as well as from finite clusters, predict Δf to be about 2.4 eV, indicating that available GW results are systematically underestimating the gap. Using the recently uncovered universal scaling between the exciton binding energy and Δf, we predict the optical gap of about 1.7 eV that can be directly related to measurements even on encapsulated samples due to its robustness against dielectric environment. The QMC gaps are indeed consistent with recent experiments based on optical absorption and photoluminescence excitation spectroscopy. We also predict the cohesion of phosphorene to be only slightly smaller than that of the bulk crystal. Our investigations not only benchmark GW methods and experiments, but also open the field of 2D electronic structure to computationally intensive but highly predictive QMC methods which include many-body effects such as electronic correlations and van der Waals interactions explicitly.Received 28 May 2018Revised 19 November 2018DOI:https://doi.org/10.1103/PhysRevX.9.011018Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBand gapCohesionPhysical Systems2-dimensional systemsPhosphoreneTechniquesCluster modelsDiffusion quantum Monte CarloFirst-principles calculationsMany-body techniquesMonte Carlo methodsVariational wave functional methodsCondensed Matter, Materials & Applied PhysicsStatistical PhysicsAtomic, Molecular & Optical