arXiv subjects

Barbara Rosa

Publications and source records attributed to Barbara Rosa.

3 recordsLinked to original sources

arXiv2024

Enhancement of interlayer exciton emission in a TMDC heterostructure via a multi-resonant chirped microresonator up to room temperature

We report on multi-resonance chirped distributed Bragg reflector (DBR) microcavities. These systems are employed to investigate the light-mater interaction with both intra- and inter-layer excitons of transition metal dichalcogenide (TMDC) bilayer heterostructures. The chirped DBRs consisting of SiO2 and Si3N4 layers with gradually changing thickness exhibit a broad stopband with a width exceeding 600 nm. Importantly, and in contrast to conventional single-resonance microcavities, our structures provide multiple resonances across a broad spectral range, which can be matched to spectrally distinct resonances of the embedded TMDC heterostructures. We study cavity-coupled emission of both intra- and inter-layer excitons from an integrated WSe2/MoSe2 heterostructure in a chirped microcavity system. We observe an enhanced interlayer exciton emission with a Purcell factor of 6.67 +- 1.02 at 4 K. Additionally, we take advantage of cavity-enhanced emission of the interlayer exciton to investigate its temperature-dependent luminescence lifetime, which yields a value of 60 ps at room temperature. Our approach provides an intriguing platform for future studies of energetically distant and confined excitons in different semiconducting materials, which paves the way for various applications such as microlasers and single-photon sources by enabling precise control and manipulation of excitonic interactions utilizing multimode resonance light-matter interaction.

cond-mat.mes-hall↗

arXiv2023

Amplification of interlayer exciton emission in twisted WSe$_2$/WSe$_2$/MoSe$_2$ heterotrilayers

Transition metal dichalcogenide (TMDC) heterostructures have unique properties that depend on the twisting angle and stacking order of two or more monolayers. However, their practical applications are limited by the low photoluminescence yield of interlayer excitons. This limits the use of layered 2D materials as a versatile platform for developing innovative optoelectronic and spintronic devices. In this study, we report on the emission enhancement of interlayer excitons in multilayered-stacked monolayers through the fabrication of heterotrilayers consisting of WSe$_2$/WSe$_2$/MoSe$_2$ with differing twist angles. Our results show that an additional WSe$_2$ monolayer introduces new absorption pathways, leading to an improvement in the emission of interlayer excitons by more than an order of magnitude. The emission boost is affected by the twist angle, and we observe a tenfold increase in the heterotrilayer area when there is a 44$^\circ$ angle between the WSe$_2$ and MoSe$_2$ materials, as opposed to their heterobilayer counterparts. Furthermore, using density functional theory, we identify the emergence of new carrier transfer pathways in the three-layer sample which extends the current understanding of 2D semiconducting heterostructures. In addition, our research provides a viable way to significantly enhance the emission of interlayer excitons. The emission enhancement of interlayer excitons is significant not only for studying the fundamental properties of interlayer excitons, but also for enabling optoelectronic applications that utilize engineered 2D quantum materials with high luminescence yield.

cond-mat.mes-hall↗

arXiv2023

Twist Angle Dependence of Exciton Resonances in WSe$_2$/MoSe$_2$ Moir\'e Heterostructures

Van der Waals heterostructures based on TMDC semiconducting materials have emerged as promising materials due to their spin-valley properties efficiently contrived by the stacking-twist angle. The twist angle drastically alters the interlayer excitonic response by determining the spatial modulation, confining moir\'e potential, and atomic reconstruction in those systems. Nonetheless, the impact of the interlayer twist angle on the band alignment of the monolayers composing the heterostructure has received scant attention in the current research. Here, we systematically investigate the twist-angle dependence of intra- and inter-layer excitons in twisted WSe2/MoSe2 heterobilayers. By performing photoluminescence excitation spectroscopy, we identify the twist-angle dependence of interlayer emission response, where an energy redshift of about 100 meV was observed for increasing twist angles. The applied microscopic theory predicts, on the contrary, a blueshift, which suggests that additional features, such as atomic reconstruction, may also surpass the moir\'e potential confinement. Those findings also prompt the effects of dielectric screening by addressing the redshift response to the stacking layer order. Furthermore, our findings support the evidence of a band offset dependence on the twist angle for the adjacent monolayers composing the heterobilayer system. Our fundamental study of exciton resonances deepens the current understanding of the physics of twisted TMDC heterostructures and paves the way for future experiments and theoretical works.

cond-mat.mes-hall↗