Darshit Solanki | Searcharxiv

arXiv2026

Moire-Engineered Excitonic Landscape and Phonon-Mediated Recombination in Twisted WSe2 Bilayers

We report light emission from the moire superlattice of a twisted bilayer of tungsten diselenide (WSe2/WSe2) encapsulated in insulating hexagonal boron nitride (hBN). The low-temperature photoluminescence (PL) spectroscopy reveals signatures of moire-potential induced strong interlayer excitonic emission and phonon-assisted recombination, while the twisting significantly suppresses the emission from localized defect-bound excitons. The moire potential redistributes carriers into indirect valleys, thereby enhancing recombination efficiency and stabilizing the interlayer excitons. Our findings establish that precise control of twist angle and dielectric environment provides a new route for engineering excitonic systems for exploring exciton-phonon interactions and associated quantum phenomena in transition metal dichalcogenides.

cond-mat.mes-hall↗

arXiv2025

Anomalies in G and 2D Raman Modes of Twisted Bilayer Graphene Near the Magic Angle

The role of twist angle ($\theta_t$) in tailoring the physical properties of heterostructures is emerging as a new paradigm in two-dimensional materials. The influence of flat electronic bands near the magic angle ($\sim$1.1$^{\circ}$) on the phononic properties of twisted bilayer graphene (t-BLG) is not well understood. In this work, we systematically investigate the G and 2D Raman modes of t-BLG samples with twist angles ranging from $\sim$0.3$^{\circ}$ to $\sim$3$^{\circ}$ using micro-Raman spectroscopy. A key finding of our work is the splitting of the G mode near the magic angle due to moir\'e potential induced phonon hybridization. The linewidth of the low-frequency component of the G mode (G$^-$), as well as the main component of the 2D mode, exhibits enhanced broadening near the magic angle due to increased electron-phonon coupling, driven by the emergence of flat electronic bands. Additionally, temperature-dependent Raman measurements (6-300 K) of magic-angle twisted bilayer graphene sample ($\theta_t \sim$ 1$^{\circ}$) reveal an almost tenfold increase in phonon anharmonicity-induced temperature variation in both components of the split G mode, as compared to Bernal-stacked bilayer graphene sample, further emphasizing the role of phonon hybridization in this system. These studies could be important for understanding the thermal properties of the twisted bilayer graphene systems.

cond-mat.mes-hall↗