arXiv subjects

Watcharaphol Paritmongkol

Publications and source records attributed to Watcharaphol Paritmongkol.

5 recordsLinked to original sources

arXiv2026

Coherent interaction of WS$_2$ and quasi-2D perovskite excitons over micrometer distances via a cavity field

The coherent coupling of cavity-confined photons and excitonic matter resonances leads to the formation of cavity polaritons, hybrid light-matter quasi-particles. If multiple exciton resonances couple to the same photonic mode, the resulting polariton constitutes a coherent interaction between matter resonances that can be spatially separated without any direct electronic coupling. In this work, we demonstrate the formation of such a coherent coupling at room temperature using an open optical cavity containing two distinct van der Waals materials - monolayer WS2 and layered quasi-2D halide perovskites (HaPs) - separated by $1.5 \mu\rm m$. The system forms three polariton branches, with the middle branch possessing nearly equal fractions of both excitons and the photonic mode. White-light reflectivity and luminescence measurements are in good agreement with simulations using a coupled harmonic oscillator and a microscopic Wannier-Hopfield framework. Our results lay the foundation to combine highly complementary degrees of freedom in 2D materials in an in-situ tunable fashion to enable new polaritonic functionalities.

cond-mat.mes-hall↗

arXiv2026

Engineering in-plane anisotropy in 2D materials via surface-bound ligands

2D materials exhibiting in-plane anisotropy enable novel functionality in electronic, optoelectronic, and photonic devices, yet their availability is generally limited to naturally-occurring low-symmetry van der Waals compounds. Here, we demonstrate an approach to structural engineering in a family of blue-emitting 2D silver phenylchalcogenide semiconductors based on steric interactions among surface-bound organic molecular ligands. By strategically halogenating specific sites of phenyl ligands, we demonstrate dramatic changes to the inorganic AgSe plane in mithrene (silver phenylselenolate, AgSePh). Density functional theory revealed pronounced in-plane electronic anisotropy for direct-gap fluorinated derivatives, while a chlorinated variant exhibited a direct-to-indirect bandgap transition. Furthermore, some fluorinated variants displayed strongly polarized absorption and luminescence, accompanied by a 10x enhancement in photoluminescence quantum yield. This work establishes a versatile approach for tailoring optoelectronic properties in hybrid semiconductors that is difficult or impossible to achieve in all-inorganic materials alone, offering new opportunities in advanced material design.

cond-mat.mtrl-sci↗

arXiv2023

Coherent Exciton-Lattice Dynamics in a 2D Metal Organochalcogenolate Semiconductor

Hybrid organic-inorganic nanomaterials can exhibit transitional behavior that deviates from models developed for all-organic or all-inorganic materials systems. Here, we reveal the complexity of exciton-phonon interactions in a recently discovered 2D layered hybrid organic-inorganic semiconductor, silver phenylselenolate (AgSePh). Using femtosecond resonant impulsive vibrational spectroscopy and non-resonant Raman scattering, we measure multiple hybrid organic-inorganic vibrational modes and identify a subset of these modes that strongly couple to the electronic excited state. Calculations by density functional perturbation theory show that these strongly coupled modes exhibit large out-of-plane silver atomic motions and silver-selenium spacing displacements. Moreover, analysis of photoluminescence fine-structure splitting and temperature-dependent peak-shifting/linewidth-broadening suggests that light emission in AgSePh is most strongly affected by a compound 100 cm-1 mode involving the wagging motion of phenylselenolate ligands and accompanying metal-chalcogen stretching. Finally, red-shifting of vibrational modes with increasing temperature reveals a high degree of anharmonicity arising from non-covalent interactions between phenyl rings. These findings reveal the unique effects of hybrid vibrational modes in organic-inorganic semiconductors and motivate future work aimed at specifically engineering such interactions through chemical and structural modification.

cond-mat.mtrl-sci↗

arXiv2023

Efficient Thermal Transport across Molecular Chains in Hybrid 2D Lead Bromide Perovskites

We report measurements of the heat capacity and cross-plane thermal conductivity of 2D (CxH2x+1NH3)2[MAPbBr3]n-1PbBr4 (MA = methylammonium) lead bromide perovskites (2D LHPs) at room temperature as a function of both the octahedral layer thickness (n = 1,2,3) and the organic spacer chain length (x=4,5,6,7,8) using differential scanning calorimetry (DSC) and frequency domain thermoreflectance (FDTR) respectively. We observe ultralow thermal conductivities (0.18-0.51 W/m K) for all 2D LHPs studied, but surprisingly minimal suppression of thermal conductivity with respect to bulk MAPbBr3 (0.5 W/m K). Cross-plane thermal conductivity is found to increase monotonically as a function of both the octahedral layer thickness (0.18-0.26 W/m K for n=1-3) and the organic chain length (0.18-0.51 W/m K for x=4-8). Additionally, we measure heat capacities that are well described by composite theory, suggesting bulk-like phonon density-of-states within the separate organic and inorganic subphases of the layered structure. The striking observation of increasing thermal conductivity with increasing organic phase fraction (i.e. increasing organic chain length) indicates efficient thermal transport along the ordered alkyl chain backbone. Our experimental results agree most closely with a predictive model of ballistic phonon transport with diffuse interface scattering - rather than normal thermal conduction within each phase. This study indicates the potential for synthesizing 2D LHPs with thermal conductivity that exceeds the bulk perovskite phase, while also shedding light on relevant phonon transport pathways in 2D LHPs.

physics.app-ph↗

arXiv2023

Discovery of enhanced lattice dynamics in a single-layered hybrid perovskite

Layered hybrid perovskites have attracted much attention in recent years due to their emergent physical properties and exceptional functional performances, but the coexistence of lattice order and structural disorder severely hinders our understanding of these materials. One unsolved problem regards how the lattice dynamics are affected by the dimensional engineering of the inorganic frameworks and the interaction with the molecular moieties. Here, we address this question by using a combination of high-resolution spontaneous Raman scattering, high-field terahertz spectroscopy, and molecular dynamics simulations. This approach enables us to reveal the structural vibrations and disorder in and out of equilibrium and provides surprising observables that differentiate single- and double-layered perovskites. While no distinct vibrational coherence is observed in double-layer perovskites, we discover that an off-resonant terahertz pulse can selectively drive a long-lived coherent phonon mode through a two-photon process in the single-layered system. This difference highlights the dramatic change in the lattice environment as the dimension is reduced. The present findings pave the way for the ultrafast structural engineering of hybrid lattices as well as for developing high-speed optical modulators based on layered perovskites.

cond-mat.mtrl-sci↗