Donor-acceptor pairs in wide-bandgap semiconductors for quantum technology applications
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2024-01-06 |
| Journal | npj Computational Materials |
| Authors | Anil Bilgin, Ian Hammock, Jeremy Estes, Yu Jin, Hannes Bernien |
| Institutions | University of Chicago |
| Citations | 14 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research proposes a new quantum science platform leveraging Donor-Acceptor Pairs (DAPs) in wide-bandgap semiconductors (Diamond and Silicon Carbide, SiC) to achieve long-range, optically controllable interactions.
- Core Mechanism: DAPs exhibit large, static electric dipole moments (up to >25 Debye) that are optically switchable, mediating coherent dipole-dipole interactions (scaling as 1/R3).
- Interaction Range: Predicted interaction strength reaches ~100 MHz at distances up to 100 nm, significantly exceeding typical solid-state spin-spin interaction ranges.
- Optimal Material Candidate: Al-N pairs in 3C-SiC are identified as the most suitable platform due to their shallow defect nature, resulting in low electron-phonon coupling.
- Spectral Resolvability: Low electron-phonon coupling in shallow DAPs (like Al-N in 3C-SiC) yields sharp, resolvable Zero-Phonon Lines (ZPLs), allowing individual pairs at different distances to be distinguished experimentally.
- Control and Tunability: ZPLs show extreme sensitivity to applied electric fields (Stark shift), enabling tunability up to a few THz, crucial for optical addressing and manipulation.
- Lifetimes: Predicted radiative lifetimes for DAPs in 3C-SiC are in the ”s range, which is sufficiently long for coherent quantum control sequences.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Host Bandgap (HSE) | 5.37 | eV | Diamond |
| Host Bandgap (HSE) | 2.25 | eV | 3C-SiC |
| Lattice Parameter (HSE) | 3.543 | A | Diamond |
| Lattice Parameter (HSE) | 4.362 | A | 3C-SiC |
| Maximum Dipole Moment | >25 | Debye | Calculated for B-N pairs in Diamond/3C-SiC |
| Dipole-Dipole Interaction Strength | ~100 | MHz | Estimated at 100 nm distance (for 15 eA dipole moment) |
| ZPL Stark Shift Tunability | Few | THz | B-N m5 shell in Diamond (under 107 V/m field) |
| Radiative Lifetime (Predicted) | ”s | Range | B-N and Al-N pairs in 3C-SiC (suitable for control) |
| Radiative Lifetime (Predicted) | ns | Range | B-N pairs in Diamond (first ten shells) |
| Optimal ZPL Energy (Al-N m7, HSE) | 2.10 - 2.25 | eV | 3C-SiC (Near experimental range 2.25-2.30 eV) |
| Electron-Phonon Coupling (B-N Diamond) | ~20 | Huang-Rhys Factor (S) | High coupling, resulting in broadband PL and poor resolvability |
| Electron-Phonon Coupling (Al-N 3C-SiC) | Small | Huang-Rhys Factor (S) | Low coupling, resulting in sharp, resolvable ZPLs |
| DFT Supercell Size | 512 | Atoms | Used for all calculations |
| Geometry Relaxation Threshold | 1 | meV/A | Force convergence criterion |
Key Methodologies
Section titled âKey Methodologiesâ- Electronic Structure Determination: Used spin-polarized Density Functional Theory (DFT) and the planewave pseudopotential method (Quantum Espresso).
- Functional Selection: Employed both the PBE semi-local functional and the screened hybrid functional HSE06. HSE06 parameters included a screening/mixing of 0.2 A-1 and 25%, respectively, yielding results closer to experimental values.
- Charge Transition Levels (CTL) Calculation: Computed CTLs (Ef[Xq]) using total energy differences between supercells containing the defect and the pristine bulk, incorporating electrostatic corrections (Ecorr).
- Electric Dipole Moment Calculation: Determined the dipole moment as the difference in polarization (ÎP) between the excited and ground states, utilizing Maximally Localized Wannier Functions (MLWF) via the Wannier90 package.
- Zero-Phonon Line (ZPL) Analysis: ZPLs were calculated using constrained DFT (CDFT) as the energy difference between the excited and ground states in their respective optimized geometries.
- Stark Shift Simulation: The ZPL shift under applied homogeneous electric fields (up to 107 V/m) was computed to assess tunability and extract the electric dipole moment from the instantaneous slope at zero field.
- Photoluminescence (PL) Spectra Simulation: PL spectra and electron-phonon coupling were modeled using the effective one-dimensional (1D) Configurational Coordinate (CC) approximation to determine Huang-Rhys factors (S) and spectral resolvability.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Information Processing: DAPs in SiC and Diamond are proposed as building blocks for solid-state quantum architectures, enabling long-range entanglement and scalable quantum networks.
- Optically Controlled Qubits: The large, switchable dipole moments allow DAPs to function as optically addressable qubits, offering a solid-state analog to vacuum Rydberg atoms.
- Nanophotonic Devices: The platform is compatible with integration into functional material heterostructures (e.g., PIN structures) and nanophotonic elements like cavities and waveguides for efficient light coupling.
- Tunable Photon Sources: DAPs can be leveraged as electronically tunable single-photon sources due to the high sensitivity of their ZPLs to applied electric fields (THz tunability).
- Quantum Memory and Storage: The predicted long radiative lifetimes (”s range in 3C-SiC) support the realization of long-lived states necessary for quantum memory and storage protocols.
View Original Abstract
Abstract We propose a quantum science platform utilizing the dipole-dipole coupling between donor-acceptor pairs (DAPs) in wide bandgap semiconductors to realize optically controllable, long-range interactions between defects in the solid state. We carry out calculations based on density functional theory (DFT) to investigate the electronic structure and interactions of DAPs formed by various substitutional point-defects in diamond and silicon carbide (SiC). We determine the most stable charge states and evaluate zero phonon lines using constrained DFT and compare our results with those of simple donor-acceptor pair (DAP) models. We show that polarization differences between ground and excited states lead to unusually large electric dipole moments for several DAPs in diamond and SiC. We predict photoluminescence spectra for selected substitutional atoms and show that while B-N pairs in diamond are challenging to control due to their large electron-phonon coupling, DAPs in SiC, especially Al-N pairs, are suitable candidates to realize long-range optically controllable interactions.