Abstract

Hexagonal boron nitride (hBN) hosts robust room-temperature single-photon emitters, yet their coherence is typically limited by phonon-induced dephasing and spectral broadening. Here, we show that thermally induced curvature in bulk-like hBN flakes provides a strain-enabled route to suppress defect–phonon coupling under ambient conditions. Nanoscale bubbles formed by thermal processing generate strong through-thickness strain gradients, which we directly probe by infrared nano-spectroscopy. These measurements reveal strain-induced splitting of in-plane phonon modes, evidencing a substantial local modification of the phonon density of states. Quantum emitters localized within these curved regions exhibit markedly enhanced room-temperature spectral purity, with Debye–Waller factors of 91% and narrower linewidths than emitters in flat regions. Photon correlation measurements confirm high-purity single-photon emission at room temperature. Supported by first-principles calculations, we attribute this behavior to strain-driven phonon redistribution, which depletes phonons in tensile regions and accumulates them in compressive regions, thereby creating locally phonon-suppressed environments for defect emitters. These results establish strain engineering as an effective route for phonon control in hBN and open a pathway toward high-coherence, room-temperature quantum light sources for integrated nanophotonic platforms.

Abstract

Hexagonal boron nitride (hBN) hosts robust room-temperature single-photon emitters, yet their coherence is typically limited by phonon-induced dephasing and spectral broadening. Here, we show that thermally induced curvature in bulk-like hBN flakes provides a strain-enabled route to suppress defect–phonon coupling under ambient conditions. Nanoscale bubbles formed by thermal processing generate strong through-thickness strain gradients, which we directly probe by infrared nano-spectroscopy. These measurements reveal strain-induced splitting of in-plane phonon modes, evidencing a substantial local modification of the phonon density of states. Quantum emitters localized within these curved regions exhibit markedly enhanced room-temperature spectral purity, with Debye–Waller factors of 91% and narrower linewidths than emitters in flat regions. Photon correlation measurements confirm high-purity single-photon emission at room temperature. Supported by first-principles calculations, we attribute this behavior to strain-driven phonon redistribution, which depletes phonons in tensile regions and accumulates them in compressive regions, thereby creating locally phonon-suppressed environments for defect emitters. These results establish strain engineering as an effective route for phonon control in hBN and open a pathway toward high-coherence, room-temperature quantum light sources for integrated nanophotonic platforms.

Abstract

Hexagonal boron nitride (hBN) hosts robust room-temperature single-photon emitters, yet their coherence is typically limited by phonon-induced dephasing and spectral broadening. Here, we show that thermally induced curvature in bulk-like hBN flakes provides a strain-enabled route to suppress defect–phonon coupling under ambient conditions. Nanoscale bubbles formed by thermal processing generate strong through-thickness strain gradients, which we directly probe by infrared nano-spectroscopy. These measurements reveal strain-induced splitting of in-plane phonon modes, evidencing a substantial local modification of the phonon density of states. Quantum emitters localized within these curved regions exhibit markedly enhanced room-temperature spectral purity, with Debye–Waller factors of 91% and narrower linewidths than emitters in flat regions. Photon correlation measurements confirm high-purity single-photon emission at room temperature. Supported by first-principles calculations, we attribute this behavior to strain-driven phonon redistribution, which depletes phonons in tensile regions and accumulates them in compressive regions, thereby creating locally phonon-suppressed environments for defect emitters. These results establish strain engineering as an effective route for phonon control in hBN and open a pathway toward high-coherence, room-temperature quantum light sources for integrated nanophotonic platforms.

Abstract

Hexagonal boron nitride (hBN) hosts robust room-temperature single-photon emitters, yet their coherence is typically limited by phonon-induced dephasing and spectral broadening. Here, we show that thermally induced curvature in bulk-like hBN flakes provides a strain-enabled route to suppress defect–phonon coupling under ambient conditions. Nanoscale bubbles formed by thermal processing generate strong through-thickness strain gradients, which we directly probe by infrared nano-spectroscopy. These measurements reveal strain-induced splitting of in-plane phonon modes, evidencing a substantial local modification of the phonon density of states. Quantum emitters localized within these curved regions exhibit markedly enhanced room-temperature spectral purity, with Debye–Waller factors of 91% and narrower linewidths than emitters in flat regions. Photon correlation measurements confirm high-purity single-photon emission at room temperature. Supported by first-principles calculations, we attribute this behavior to strain-driven phonon redistribution, which depletes phonons in tensile regions and accumulates them in compressive regions, thereby creating locally phonon-suppressed environments for defect emitters. These results establish strain engineering as an effective route for phonon control in hBN and open a pathway toward high-coherence, room-temperature quantum light sources for integrated nanophotonic platforms.