Hierarchical spectral inhomogeneity in photoluminescence of a twisted MoSe2/WSe2 heterobilayer moir\'e superlattice revealed by hyperspectral mapping

TL;DR

This study uses hyperspectral mapping to reveal hierarchical spatial organization and inhomogeneity in the photoluminescence spectra of twisted MoSe2/WSe2 heterobilayer superlattices, uncovering micron-scale domains and complex local spectral manifolds.

Contribution

It introduces a spectral analysis approach that uncovers hierarchical inhomogeneity and spatial organization in the photoluminescence of moiré superlattices, advancing understanding of their spectral complexity.

Findings

Identified three dominant spectral families forming micron-scale domains.

Established a characteristic length scale of 1.27-2.05 μm exceeding optical spot size.

Revealed hierarchical organization of spectral features and local spectral manifolds.

Abstract

Low-temperature photoluminescence from MoSe2/WSe2 moir\'e superlattice often consists of a broad interlayer emission background with dense, narrow peaks, making microscopic line-by-line assignment difficult. Here, we use hyperspectral photoluminescence mapping and peak-decomposition-free spectral analyses to determine how this spectral complexity is organized in space. A 20 x 20 map acquired with a 400 nm pitch reveals three dominant spectral families that form contiguous real-space domains. Feature-wise spatial correlation analysis and whole-spectrum similarity yield a characteristic micron-scale length of 1.27-2.05 um, all exceeding the 0.85 um optical spot size. At the same time, individual pixels retain a dense, multi-peak structure, implying an unresolved local spectral manifold below optical resolution. Correlations among centroid, dominant energy, asymmetry, width, entropy, sharp fraction, and roughness indicate that the micron-scale energy landscape and local manifold complexity can be statistically separated, while remaining correlated across the map, consistent with a hierarchical organization of the emission spectrum. These results establish hierarchical inhomogeneity as an organizing principle of MoSe2/WSe2 moir\'e superlattice photoluminescence.