Paul Bittorf | Searcharxiv

arXiv2025

Exciton Energy Routing via Defect Networks in hBN/2D-Perovskite Hybrids

Excitons in two dimensional Ruddlesden Popper perovskites (RPPs) exhibit large and tunable binding energies, making them promising candidates for optoelectronic applications. In particular, long-range exciton energy transfer in these materi-als holds potential for light-harvesting technologies and nanoscale interconnects. Here, using cathodoluminescence spectros-copy, we demonstrate that exciton energy can be transferred over ultralong distances, up to 150 micrometers, in heterostructures composed of hexagonal boron nitride (hBN) and RPPs. This transfer is enabled by efficient exciton coupling to defect centers in hBN and subsequent defect defect interactions. This mechanism not only facilitates long-range energy transfer, but also leads to enhanced luminescence intensity, narrower emission linewidths, extended exciton lifetimes, and reduced electron-beam-induced degradation. Owing to the high density of emitters within the hBN layers, the investigated van der Waals heterostructure emerges as a robust and stable hybrid platform. Our findings open promising pathways for room-temperature excitonic devices with enhanced performance, including quantum transducers, light-harvesting systems, and optoelectronic interconnects.

cond-mat.mes-hall↗

arXiv2024

Ultrafast phonon-mediated dephasing of color centers in hexagonal boron nitride probed by electron beams

Defect centers in hexagonal boron nitride have been extensively studied as room temperature single photon sources. The electronic structure of these defects exhibits strong coupling to phonons, as evidenced by the observation of phonon sidebands in both photoluminescence and cathodoluminescence spectra. However, the dynamics of the electron phonon coupling as well as phonon mediated dephasing of the color centers in hexagonal boron nitride remain unexplored. Here, we apply a novel time resolved CL spectroscopy technique to explore the population decay to phonon states and the dephasing time T2 with sub femtosecond time resolution. We demonstrate an ultrafast dephasing time of only 200 fs and a radiative decay of about 585 fs at room temperature, in contrast with all optical time resolved photoluminescence techniques that report a decay of a few nanoseconds. This behavior is attributed to efficient electron-beam excitation of coherent phonon polaritons in hexagonal boron nitride, resulting in faster dephasing of electronic transitions. Our results demonstrate the capability of our sequential cathodoluminescence spectroscopy technique to probe the ultrafast dephasing time of single emitters in quantum materials with sub femtosecond time resolution, heralding access to quantum path interferences in single emitters coupled to their complex environment.

quant-ph↗