Unconventional excitonic states with phonon sidebands in layered silicon diphosphide

Abstract

Complex correlated states emerging from many-body interactions between quasiparticles (electrons, excitons and phonons) are at the core of condensed matter physics and material science. In low-dimensional materials, quantum confinement affects the electronic, and subsequently, optical properties for these correlated states. Here, by combining photoluminescence, optical reflection measurements and ab initio theoretical calculations, we demonstrate an unconventional excitonic state and its bound phonon sideband in layered silicon diphosphide (SiP2), where the bound electron–hole pair is composed of electrons confined within one-dimensional phosphorus–phosphorus chains and holes extended in two-dimensional SiP2 layers. The excitonic state and emergent phonon sideband show linear dichroism and large energy redshifts with increasing temperature. Our ab initio many-body calculations confirm that the observed phonon sideband results from the correlated interaction between excitons and optical phonons. With these results, we propose layered SiP2 as a platform for the study of excitonic physics and many-particle effects.

Unconventional Anisotropy in Excitonic Properties and Carrier Mobility in Iodine-Based XTeI (X = Ga, In) Monolayers for Visible-Light Photocatalytic Water Splitting

“…Reduced dielectric screen- electron−hole separation or spatial delocalization, also called exciton Bohr radius) and exciton binding energy, remarkably different from those in bulk materials. 14 Increased Coulomb interaction, as discussed above, significantly hinders the dissociation of photoinduced electron−hole pairs, which in turn can severely limit the photocatalytic activity. Herein, employing GW approximation, we have not only analyzed the behavior of excitons arising in GaTeI and InTeI monolayers in the different dielectric environments but also have shown that the presence of a dielectric environment significantly reduces the exciton binding energy that is desirable for charge separation.…”

“…Moreover, materials with reduced dimensionality present a new avenue for fundamental exciton physics. − The ultrathin nature of 2D materials, that is, strong geometrical confinement, causes weak dielectric screening, which gives rise to increased Coulomb interaction. Reduced dielectric screening and enhanced Coulomb interaction in 2D materials can cause exciton properties, like exciton extension (bound electron–hole separation or spatial delocalization, also called exciton Bohr radius) and exciton binding energy, remarkably different from those in bulk materials . Increased Coulomb interaction, as discussed above, significantly hinders the dissociation of photoinduced electron–hole pairs, which in turn can severely limit the photocatalytic activity.…”

2D SiP2/h-BN for a Gate-Controlled Phototransistor with Ultrahigh Sensitivity

“…However, most of them are not competent for ultrasensitive photodetection owing to the high dark currents and low detectivity. , Recently, a new family of group IV and group V 2D layered materials such as GeP, GeAs 2 , SiAs 2 , SiP, and SiP 2 have emerged as promising candidate 2D materials for high-performance photoelectric devices. − As an important member of group IV and group V 2D materials, SiP 2 is a new semiconductor with a tunable bandgap (1.99–2.25 eV), strong light absorption ability, and excellent air stability. − In addition, the high carrier mobility of 1.069 × 10 5 cm 2 V –1 s –1 was theoretically predicted for monolayer SiP 2 , which can be comparable to that of graphene . Notably, the intrinsic anisotropic structure induced by zigzag phosphorus–phosphorus chains in 2D SiP 2 directly results in unique physical properties, revealing an unconventionally bright exciton with hybrid dimensionality of band-edge states . However, to date, the field effect transistor (FET) properties and gate-controlled phototransistor of SiP 2 have not yet been explored, not to mention its ultrasensitive phototransistor performance.…”

“…16 Notably, the intrinsic anisotropic structure induced by zigzag phosphorus−phosphorus chains in 2D SiP 2 directly results in unique physical properties, revealing an unconventionally bright exciton with hybrid dimensionality of band-edge states. 17 However, to date, the field effect transistor (FET) properties and gate-controlled phototransistor of SiP 2…”

Anharmonic Exciton‐Phonon Coupling in Metal‐Organic Chalcogenides Hybrid Quantum Wells

“…[6,7] Overall our results highlight the general importance of exciton coupling to optical phonons in this class of materials and they further suggest that also the peculiar spatial symmetry of the excitonic states and phonon modes needs to be accounted for in a proper treatment of exciton−phonon coupling. [21]…”