Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2609.32909

Parity-selected Bethe-Salpeter equation: symmetry-adapted regularization of the exciton-phonon self-energy in polar semiconductors

Michael O. Atambo
View original source ↗Read source document ↗Export metadata ↓

Abstract

Finite-temperature Bethe-Salpeter calculations of exciton-phonon self-energies in polar materials are bottlenecked by the Fröhlich divergence of the intra-1s scattering vertex. We show that for a bound electron-hole pair this divergence is analytically eliminated by electron-hole interference: the intra-1s vertex admits the exact factorization $V_{\mathrm{el}}(q)=q\,\mathcal G(q)$ with $\mathcal G(0)\propto(m_h-m_e)/(m_h+m_e)$, vanishing identically for equal masses (parity protection). A multipole interference factor $\mathcal I_n=β_e^{\,n}-(-β_h)^{n}$ determines where the singularity survives-only in dipole-allowed inter-state channels. We formulate a parity-selected truncation of the exciton-phonon self-energy in which the intra-1s channel is evaluated exactly at negligible cost, converging with $10^2$-$10^3$ fewer $q$-points. We find that the regularized intra-1s channel, previously obscured by numerical cutoffs, controls the temperature-dependent exciton shift in mass-asymmetric polar semiconductors.

Explore related subjects

cond-mat.mtrl-sci

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Michael O. Atambo. 2026-09-26. Parity-selected Bethe-Salpeter equation: symmetry-adapted regularization of the exciton-phonon self-energy in polar semiconductors. https://arxiv.org/abs/2609.32909

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Fine Oxide Dispersoids Modulate Phonon Drag and Dislocation Relaxation in Dynamically Deformed Superalloys

Plastic deformation in metallic alloys is primarily governed by the motion of dislocations, which are atomic scale line defects that move through the crystal lattice under an applied stress. Superalloys containing fine oxide particles withstand extreme temperatures for prolonged durations by resisting dislocation motion. This thermally controlled mechanism conventionally involves dislocations first climbing over the particle and slowly detaching from it, a process that typically occurs on the order of seconds. However, these mechanisms drastically change when dislocation velocities increase, potentially exceeding half the shear wave speed of the material. At such extreme speeds, dislocations can interact with lattice vibrations, leading to pronounced phonon interactions. We leverage a pulsed laser to drive rigid microspheres at controlled velocities towards superalloy substrates containing a dense oxide dispersion. Synchronized high speed imaging allows precise mapping of deformation events, allowing high throughput decoupling and modeling of plasticity contributions. We find that the oxide network produces a dual and counterintuitive effect. Our modeling framework indicates that rapidly moving dislocations bypass oxide particles by bowing rather than climbing, thereby suppressing departure side dislocation relaxation. At the same time, the dense oxide network confines fast moving dislocations within the critical interparticle distance, thereby reducing their interaction with phonons. These findings shed light on new plasticity mechanisms in oxide particle containing superalloys when line defects accelerate and dissipate energy on picosecond timescales.

cond-mat.mtrl-sci↗
arXiv2026

Oxygen deficiency and valency reconstruction in multiferroic V-doped HfO$_2$

The interplay of oxygen deficiency and vanadium multiple valency in the candidate multiferroic V-doped $Pca2_1$ hafnia HfO$_2$ is studied by first-principles calculations. Low-lying V majority gap states accept electrons from oxygen-vacancy donors, reducing their formation energy, and converting nominal V$^{4+}$ centers into V$^{3+}$. The resulting local magnetization and screening changes are reflected in the calculated V core-level shifts, which are consistent with the experimentally observed XPS signatures. The calculated V$^{3+}$/V$^{4+}$ population ratio determined by oxygen vacancies only matches experiment in reducing conditions, suggesting that additional electron reservoirs may contribute under ALD growth conditions. A similar scenario also seems to apply to the recently observed multiferroicity in Cr-doped hafnia, where oxygen deficiency is intrinsic to the growth technique.

cond-mat.mtrl-sci↗
arXiv2026

Defect-controlled twin activation in crystallographically equivalent magnesium micropillars

Tensile twinning plays a central role in accommodating -axis plasticity in Mg. In bulk Mg, it typically shows a relatively deterministic response with a low critical stress, whereas in confined volumes it exhibits broad yield-stress distributions that complicate the prediction of small-scale mechanical behavior. Here, site-specific compression tests are performed on 4 $μ$m-diameter pillars fabricated in a parent Mg crystal and an adjacent {10-12} twin. The two regions share the same [11-20] compression axis but experienced different prior deformation histories, allowing the influence of the residual microstructural state to be examined at fixed crystallographic orientation. Among 27 pillars, most parent-region pillars yield near 300 MPa, whereas pillars from the twin region span approximately 30 to 300 MPa. Interrupted tests combined with cross-sectional EBSD link individual load drops to discrete twin formation and further show that a pillar containing a pre-existing twin yields at approximately 80 MPa through the migration of the existing twin boundary. Molecular dynamics simulations of 30 nm-diameter pillars resolve possible atomistic pathways at the nanoscale. The simulations illustrate how contact geometry and pre-existing twin embryos alter event selection, and how an activated twin advances rapidly, while coherent twin boundary migration proceeds through disconnection motion accompanied by crystallographically required atomic shuffles. The results attribute the experimental scatter to the local availability of embryos and mobile interfaces, such that the first plastic event is governed by the twinning pathway accessible from the local microstructural state rather than by a single characteristic critical stress. Deformation history can therefore strongly modify the distribution of first plastic events even when the loading orientation is fixed.

cond-mat.mtrl-sci↗