Biexcitonexciton

Biexcitonexciton is a term encountered in semiconductor optics to denote a bound three-exciton complex, effectively a triexciton formed by binding a biexciton to an additional exciton. Terminology varies in the literature: some authors describe it as a biexciton–exciton complex emphasizing its constituent parts, while others simply call it a triexciton.

Formation and binding occur in materials where Coulomb interactions between electrons and holes are strong and where multi-exciton states can be stabilized by confinement or reduced dimensionality. This includes quantum wells, quantum dots, and two-dimensional materials such as transition metal dichalcogenide monolayers. The binding energy of such a complex depends on the material, its dielectric environment, and the degree of quantum confinement; reported energies span a range from a few meV up to several tens of meV in various systems. The existence and stability are sensitive to temperature and excitation conditions.

Spectroscopic signatures would include discrete optical features at energies below the sum of a biexciton and an exciton, reflecting the complex’s binding energy. Its radiative decay can proceed via cascaded recombination, producing photons associated with successive loss of excitons. In practice, disentangling a bona fide biexciton–exciton complex from other multi-exciton states requires careful analysis of power dependence, temperature behavior, and time-resolved decay dynamics.

Materials research and theory continue to investigate such higher-order exciton complexes. Experimental observations often rely on high-quality, low-temperature samples and precise spectroscopic techniques, while theoretical models employ few-body quantum mechanics to estimate binding energies and interpret spectra. Related concepts include excitons, biexcitons, triexcitons, and other multi-exciton states in nanostructures and two-dimensional semiconductors.