Search NASA⌕ Search

SEARCH · Search NASA

Results for “excitonic vertex corrections”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

3 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Paramagnetic electronic structure of CrSBr: Comparison between ab initio G W theory and angle-resolved photoemission spectroscopy

Here, we explore the electronic structure of paramagnetic CrSBr by comparative first-principles calculations and angle-resolved photoemission spectroscopy. We theoretically approximate the paramagnetic phase using a supercell hosting spin configurations with broken long-range order and applying quasiparticle self-consistent GW theory, without and with the inclusion of excitonic vertex corrections to the screened Coulomb interaction (QS GW and QS $G\widehat{W}$, respectively). Comparing the quasiparticle band-structure calculations to angle-resolved photoemission data collected at 200 K results in excellent agreement. This allows us to qualitatively explain the significant broadening of some bands as arising from the broken magnetic long-range order and/or electronic dispersion perpendicular to the quasi-two-dimensional layers of the crystal structure. The experimental band gap at 200 K is found to be at least 1.51 eV at 200 K. At lower temperature, no photoemission data can be collected as a result of charging effects, pointing towards a significantly larger gap, which is consistent with the calculated band gap of approximately 2.1 eV.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Excitons in 2D Magnets

Theoretical abilities that we built: In our QSGW formalism, the electronic eigenfunctions are calculated self-consistently in presence of the ladder e-h vertex corrections to the screened Coulomb exchange. Charge and self-energies are recalculated iterated until the desired tolerance is achieved in the one-particle Green's function. Further, to include the multi-determinantal (spin-flip structure of multiplets) nature of many body correlations we combine QSGW with DMFT. Below we explore various classes of strongly correlated magnetic systems where excitons are sufficiently described within either the QSGW or the QSGW +DMFT approach. In the process, we establish the digrammatic requirements for a minimum-sufficient theory for describing excitons in large classes of materials.

2D magnets↗
DOE OSTI2022

Electronic and optical properties of crystalline nitrogen versus black phosphorus: A comparative first-principles study

We report crystalline black nitrogen (BN) is an allotrope of nitrogen with the black phosphorus (BP) structure recently synthesized at high pressure by two independent research groups. Here, we present a systematic study of the electronic and optical properties of BN focusing on its comparison with BP. To this end, we use the state-of-the-art quasiparticle self-consistent GW approach with vertex corrections in both the electronic and optical channels. Despite many similarities, the properties of BN are found to be considerably different. Unlike BP, BN exhibits a larger optical gap (2.5 vs 0.26 eV), making BN transparent in the visible spectral region with a highly anisotropic optical response. This difference can be primarily attributed to a considerably reduced dielectric screening in BN, leading to enhancement of the effective Coulomb interaction. Despite relatively strong Coulomb interaction, exciton formation is largely suppressed in both materials. Our analysis of the elastic properties shows exceptionally high stiffness of BN, comparable to that of diamond.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗