Radiative electronic bound states in the continuum from defects in semiconductors

Ki Hoon Lee; Liang Z. Tan; Seong Yun Hong; Yeonghun Lee; Youngho Kang

arxiv: 2605.26841 · v1 · pith:K32T4KM7new · submitted 2026-05-26 · ❄️ cond-mat.mtrl-sci · quant-ph

Radiative electronic bound states in the continuum from defects in semiconductors

Seong Yun Hong , Liang Z. Tan , Ki Hoon Lee , Youngho Kang , Yeonghun Lee This is my paper

Pith reviewed 2026-06-29 17:08 UTC · model grok-4.3

classification ❄️ cond-mat.mtrl-sci quant-ph

keywords bound states in the continuumdefect statessilicon G-centerradiative emissionnonradiative decayfirst-principles calculationsexchange interactionphotoluminescence

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The pith

Defect states buried below the valence band in silicon become radiative after an exchange-driven level shift upon optical excitation.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes that defect states embedded in the electronic continuum of semiconductors, normally expected to be optically inactive, can instead support radiative bound states in the continuum. Calculations on the silicon G-center show that optical excitation triggers an exchange-driven reordering that moves a localized defect level from below to above the valence band maximum. This change reduces nonradiative coupling and produces emission whose temperature dependence matches measured photoluminescence lifetimes. The work identifies a stabilization route for such defects and frames electronic BICs as a design principle for optical defect systems.

Core claim

Hybrid-functional first-principles calculations with a Hubbard U correction reveal that a localized defect state, initially buried below the valence band maximum in the ground state, undergoes exchange-driven energy-level reordering under optical excitation and shifts above the VBM. This exchange-induced transition suppresses nonradiative decay and enables robust radiative emission. By computing temperature-dependent nonradiative lifetimes and comparing them with experimental photoluminescence lifetimes, the calculations quantitatively reproduce the observed temperature dependence of the emission.

What carries the argument

exchange-driven energy-level reordering of a localized defect state that moves it above the valence band maximum under optical excitation

If this is right

Continuum-buried defect states can host radiative electronic bound states in the continuum.
The exchange-induced transition suppresses nonradiative decay and enables robust radiative emission from such defects.
Computed temperature-dependent nonradiative lifetimes reproduce the observed temperature dependence of photoluminescence for the silicon G-center.
Electronic BICs offer a general paradigm for designing defect-based optical systems including quantum emitters and qubits.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

The reordering mechanism could occur in other defect centers or host materials, suggesting a broader class of radiative continuum states.
Intentional design of defects that sit inside the continuum might become viable if optical excitation reliably triggers the stabilizing shift.
Similar exchange effects might explain unexpected radiative signals in other systems previously assumed to be non-emissive due to continuum embedding.

Load-bearing premise

The hybrid-functional DFT calculation with Hubbard U correctly captures the exchange-driven reordering of defect levels under excitation so that the resulting nonradiative lifetimes can be compared directly to experimental photoluminescence data.

What would settle it

An excited-state calculation or measurement showing the defect level remains below the valence band maximum, or a clear mismatch between the computed and measured temperature dependence of photoluminescence lifetimes in the silicon G-center, would falsify the mechanism.

read the original abstract

Continuum-buried defect states in semiconductors are generally expected to be optically inactive due to their strong coupling to continuum bands. Here, we show that such defects can instead host radiative electronic bound states in the continuum (BICs), using the silicon G-center as a prototypical example. Hybrid-functional first-principles calculations with a Hubbard $U$ correction reveal that a localized defect state, initially buried below the valence band maximum (VBM) in the ground state, undergoes exchange-driven energy-level reordering under optical excitation and shifts above the VBM. This exchange-induced transition suppresses nonradiative decay and enables robust radiative emission. By computing temperature-dependent nonradiative lifetimes and comparing them with experimental photoluminescence (PL) lifetimes, we quantitatively reproduce the observed temperature dependence of the emission. These results uncover a stabilization mechanism for continuum-embedded defect states and establish electronic BICs as a general paradigm for designing defect-based optical systems, including quantum emitters and qubits.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

The G-center work shows a plausible exchange reordering mechanism for turning a buried defect into a radiative BIC, but the result sits on a single choice of hybrid mixing and U with no visible robustness checks.

read the letter

The core claim is that optical excitation in the silicon G-center drives an exchange-driven shift that moves a defect level from below the VBM to above it, turning a continuum-buried state into a radiative BIC and cutting off nonradiative paths. The authors then compute temperature-dependent nonradiative lifetimes that track experimental PL data.

What is actually new is the explicit framing of this reordering as a stabilization route for continuum-embedded defects, with the G-center as the worked example. The attempt to link the calculated lifetimes directly to measured temperature dependence is a concrete step beyond pure electronic-structure arguments.

The calculations use hybrid DFT plus Hubbard U, which is a standard route for defect levels. That part is executed competently enough on its own terms.

The soft spot is exactly the one flagged in the stress-test note. The reordering and the subsequent lifetime match both depend on the specific hybrid mixing fraction and the value of U. The abstract and the reported workflow give no indication that these were varied or anchored to independent observables. If a modest change in either parameter reverses the sign of (E_defect - E_VBM), the claimed mechanism does not survive. The lifetime comparison then becomes dependent on the same choice rather than an independent test.

This paper is aimed at people working on defect-based emitters and qubits in group-IV materials. A reader already thinking about silicon photonics or G-center engineering would find the proposed design principle useful to consider.

It is worth sending to referees. The mechanism is specific enough that a careful review can check the parameter sensitivity and the lifetime methodology directly.

Referee Report

2 major / 1 minor

Summary. The manuscript uses hybrid-functional DFT with a Hubbard U correction to study the silicon G-center defect. It claims that a localized defect state lies below the VBM in the ground-state configuration but undergoes an exchange-driven reordering to lie above the VBM in the optically excited configuration. This reordering is asserted to suppress nonradiative decay channels, enabling radiative emission from an electronic bound state in the continuum. Temperature-dependent nonradiative lifetimes computed from this mechanism are reported to quantitatively reproduce the temperature dependence of experimental photoluminescence lifetimes.

Significance. If the exchange-driven reordering and resulting lifetime match prove robust, the work would identify a concrete stabilization mechanism for continuum-buried defect states and position electronic BICs as a design principle for defect-based emitters and qubits. The attempt to connect first-principles energetics directly to measured temperature dependence is a positive feature, though its weight is currently limited by the absence of reported sensitivity tests on the tunable parameters.

major comments (2)

[Abstract] Abstract: the central claim that the hybrid-functional plus Hubbard U calculation produces a defect level that lies below the VBM in the ground state but above it under optical excitation rests on a single choice of U and hybrid mixing parameter. No demonstration is given that the sign of (E_defect − E_VBM) is preserved under modest variations of these parameters, which directly affects whether the claimed suppression of nonradiative decay is mechanism-driven or parameter-dependent.
[Abstract] The temperature-dependent nonradiative lifetime calculation (abstract): the quantitative reproduction of experimental PL temperature dependence is presented without reported error bars, convergence tests with respect to supercell size or k-point sampling, or explicit statement of how the Hubbard U value was fixed from external data rather than adjusted to the lifetime data.

minor comments (1)

Notation for the defect level position relative to the VBM should be defined consistently between ground and excited configurations to avoid ambiguity in the reordering claim.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the thoughtful review and for highlighting the need for additional robustness checks. We agree that the central claims would be strengthened by explicit sensitivity analysis and methodological details. Below we respond point-by-point to the major comments and indicate the revisions we will make.

read point-by-point responses

Referee: [Abstract] Abstract: the central claim that the hybrid-functional plus Hubbard U calculation produces a defect level that lies below the VBM in the ground state but above it under optical excitation rests on a single choice of U and hybrid mixing parameter. No demonstration is given that the sign of (E_defect − E_VBM) is preserved under modest variations of these parameters, which directly affects whether the claimed suppression of nonradiative decay is mechanism-driven or parameter-dependent.

Authors: We agree that the robustness of the level reordering with respect to the hybrid mixing parameter and U should be demonstrated explicitly. In the revised manuscript we will add a dedicated subsection (or supplementary note) reporting the defect level position relative to the VBM for a range of hybrid fractions (0.25–0.35) and U values around the chosen value, confirming that the sign change upon excitation remains. This will clarify that the mechanism is not an artifact of the specific parameter choice. revision: yes
Referee: [Abstract] The temperature-dependent nonradiative lifetime calculation (abstract): the quantitative reproduction of experimental PL temperature dependence is presented without reported error bars, convergence tests with respect to supercell size or k-point sampling, or explicit statement of how the Hubbard U value was fixed from external data rather than adjusted to the lifetime data.

Authors: We acknowledge these omissions. In the revision we will (i) state explicitly how the U value was determined from independent literature or fitting to ground-state properties (not to the PL lifetimes), (ii) report convergence tests with supercell size and k-point sampling for the key energies and matrix elements entering the lifetime calculation, and (iii) include error bars or uncertainty estimates on the computed temperature-dependent lifetimes. These additions will be placed in the methods/results section and referenced from the abstract. revision: yes

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper's derivation begins with hybrid-functional DFT plus Hubbard U calculations that output the ground-state defect level position below the VBM and the excited-state reordering above it; this electronic structure result is not equivalent to any input by construction. Nonradiative lifetimes are subsequently computed from the resulting energy levels and transition rates, then compared to external experimental PL data to reproduce temperature dependence. No step renames a fitted parameter as a prediction, invokes a self-citation as the sole justification for a uniqueness claim, or smuggles an ansatz via prior work. The central mechanism is an output of the first-principles method applied to the defect system, and the lifetime comparison constitutes an independent external benchmark rather than a tautology.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on the accuracy of hybrid DFT plus a Hubbard U correction for capturing exchange effects in excited defect states and on the direct interpretability of computed nonradiative lifetimes as predictors of experimental PL.

free parameters (1)

Hubbard U correction
Added to the hybrid-functional calculation to adjust defect-state energies; value not specified in abstract.

axioms (2)

domain assumption Hybrid-functional DFT with Hubbard U accurately describes exchange-driven level reordering in optically excited defect states
Invoked to justify the energy shift above VBM and the resulting suppression of nonradiative decay.
domain assumption Computed temperature-dependent nonradiative lifetimes can be compared quantitatively to experimental PL lifetimes without additional scaling or selection
Used to claim reproduction of observed temperature dependence.

pith-pipeline@v0.9.1-grok · 5707 in / 1488 out tokens · 44244 ms · 2026-06-29T17:08:26.831935+00:00 · methodology

discussion (0)

Reference graph

Works this paper leans on

2 extracted references · 2 canonical work pages

[1]

(1) Alkauskas, A.; Yan, Q.; Van De Walle, C. G. First-Principles Theory of Nonradiative Carrier Capture via Multiphonon Emission. Phys. Rev. B 2014, 90 (7), 075202. https://doi.org/10.1103/PhysRevB.90.075202. (2) Turiansky, M. E.; Alkauskas, A.; Engel, M.; Kresse, G.; Wickramaratne, D.; Shen, J.-X

work page doi:10.1103/physrevb.90.075202 2014
[2]

E.; Van De Walle, C

Dreyer, C. E.; Van De Walle, C. G. Nonrad: Computing Nonradiative Capture Coefficients from First Principles. Computer Physics Communications 2021, 267, 108056. https://doi.org/10.1016/j.cpc.2021.108056

work page doi:10.1016/j.cpc.2021.108056 2021

[1] [1]

(1) Alkauskas, A.; Yan, Q.; Van De Walle, C. G. First-Principles Theory of Nonradiative Carrier Capture via Multiphonon Emission. Phys. Rev. B 2014, 90 (7), 075202. https://doi.org/10.1103/PhysRevB.90.075202. (2) Turiansky, M. E.; Alkauskas, A.; Engel, M.; Kresse, G.; Wickramaratne, D.; Shen, J.-X

work page doi:10.1103/physrevb.90.075202 2014

[2] [2]

E.; Van De Walle, C

Dreyer, C. E.; Van De Walle, C. G. Nonrad: Computing Nonradiative Capture Coefficients from First Principles. Computer Physics Communications 2021, 267, 108056. https://doi.org/10.1016/j.cpc.2021.108056

work page doi:10.1016/j.cpc.2021.108056 2021