Quasiparticle effects and strong excitonic features in exfoliable 1D semiconducting materials

TL;DR

The paper addresses the optoelectronic properties of exfoliable one-dimensional chains derived from van der Waals-bonded crystals, focusing on S3, Te3, As2S3, and Bi2Te3. It employs a fully first-principles workflow combining DFT, DFPT, GW, and BSE to capture quasiparticle gaps and excitons in these 1D wires. The results reveal extremely strong exciton binding energies in the range $0.33$–$2.27$ eV, Wannier-Mott-like excitons in the elemental chains, and continuum-like spectra with smaller binding in the polar/ionic chains, with optical gaps spanning infrared to ultraviolet. A two-band EMA with a screened 1D Coulomb potential explains the trends and highlights the critical role of 1D electronic polarizability in screening, pointing to strong potential for room-temperature excitonic devices and broadband nanoscale optoelectronics.

Abstract

We report a comprehensive first-principles study of the electronic and optical properties of recently identified exfoliable one-dimensional semiconducting materials, focusing on chalcogenide-based atomic chains derived from van der Waals-bonded bulk crystals. Specifically, we investigate covalently bonded S3 and Te3 chains, and polar-bonded As2S3 and Bi2Te3 chains, using a fully first-principles approach that combines density-functional theory (DFT), density-functional perturbation theory (DFPT), and many-body perturbation theory within the GW approximation and Bethe-Salpeter equation (BSE). Our vibrational analysis shows that freestanding isolated wires remain dynamically stable, with the zone-center optical phonon modes leading to infrared activity. The main finding of this study is the presence of very strong exciton binding energies (1-3 eV), which make these novel 1D materials ideal platforms for room-temperature excitonic applications. Interestingly, the exciton character remains Wannier-Mott-like, as indicated by average electron-hole separations larger than the lattice constant. Notably, the optical gaps of these materials span a wide range - from infrared (0.8 eV, Bi2Te3), through visible spectrum (yellow: 2.17 eV, Te3; blue: 2.71 eV, As2S3), up to ultraviolet (4.07 eV, S3) - highlighting their versatility for broadband optoelectronic applications. Our results offer a detailed, many-body perspective on the optoelectronic behavior of these low-dimensional materials and underscore their potential for applications in next-generation nanoscale optoelectronic devices.

Figures (7)

• Figure 1: Optimized geometric structures of $(\mathbf{a})$$\mathrm{S}_3$, $(\mathbf{b})$$\mathrm{Te}_3$, $(\mathbf{c})$$\mathrm{As}_2\mathrm{S}_3$ and $(\mathbf{d})$$\mathrm{Bi}_2\mathrm{Te}_3$. The optimized lattice parameters of the unit cells are also displayed.
• Figure 2: [Top] Phonon band structures of $(\mathbf{a})$$\mathrm{S}_3$, $(\mathbf{b})$$\mathrm{Te}_3$, $(\mathbf{c})$$\mathrm{As}_2\mathrm{S}_3$ and $(\mathbf{d})$$\mathrm{Bi}_2\mathrm{Te}_3$, calculated at harmonic level within DFPT. [Bottom] Top-view of (from left to right) $\mathrm{S}_3$, $\mathrm{Te}_3$, $\mathrm{As}_2\mathrm{S}_3$, $\mathrm{Bi}_2\mathrm{Te}_3$ with arrows indicating the displacements produced by TWA at $\Gamma$.
• Figure 3: IR absorption spectra of $(\mathbf{a})$$\mathrm{S}_3$, $(\mathbf{b})$$\mathrm{Te}_3$, $(\mathbf{c})$$\mathrm{As}_2\mathrm{S}_3$ and $(\mathbf{d})$$\mathrm{Bi}_2\mathrm{Te}_3$, calculated at harmonic level of theory in DFPT. Insets show the corresponding vibrations of the main IR-active modes. The colors of the atoms are yellow (S), blue (Te), green (As) and red (Bi).
• Figure 4: IR absorption peaks of the four nanowires. The IR response of S$_3$ and Te$_3$ is multiplied by a factor of 50 in the plot, as extremely weak (and otherwise indistinguishable) compared to the most prominent peaks of As$_2$S$_3$ and Bi$_2$Te$_3$.
• Figure 5: [Left] Absorption spectra (solid blue) of $(\mathbf{a})$$\mathrm{S}_3$ and $(\mathbf{d})$$\mathrm{Te}_3$, expressed in terms of the optical absorbance $A(\omega)$, calculated at the ev$GW/$BSE level. The corresponding ev$GW-$corrected direct electronic band gaps (dashed red) are shown as a reference (6.34 eV for S$_3$). A broadening of 50 meV was used. [Right] Electronic band structures (solid grey), calculated at the ev$GW$ level, of $\mathrm{S}_3$$(\mathbf{b}-\mathbf{c})$ and $\mathrm{Te}_3$$(\mathbf{e}-\mathbf{f})$. The colored dots (red and green) represent the single-particle transitions contributing to the first two bright excitons, and their size is proportional to the intensity of the transition - renormalized to the highest value. The corresponding excitonic peaks are highlighted in the relative absorption spectra (solid red and green), together with other meaningful higher excitations below the electronic gap (see Fig. 12 in the SI). Energy zero is set as the top of the valence bands. SOC and semi-core corrections were included.