Large bulk photovoltaic effect and spontaneous polarization of single-layer monochalcogenides (1610.06589v2)

Abstract: We use a first-principles density functional theory approach to calculate the shift current and linear absorption of uniformly illuminated single-layer Ge and Sn monochalcogenides. We predict strong absorption in the visible spectrum and a large effective three-dimensional shift current ($\sim$100 $\mu$A/V$^2$), larger than has been previously observed in other polar systems. Moreover, we show that the integral of the shift-current tensor is correlated to the large spontaneous effective three-dimensional electric polarization ($\sim$1.9 C/m$^2$). Our calculations indicate that the shift current will be largest in the visible spectrum, suggesting that these monochalcogenides may be promising for polar optoelectronic devices. A Rice-Mele tight-binding model is used to rationalize the shift-current response for these systems, and its dependence on polarization, in general terms with implications for other polar materials

Large Bulk Photovoltaic Effect and Spontaneous Polarization in Single-Layer Monochalcogenides

The paper "Large Bulk Photovoltaic Effect and Spontaneous Polarization of Single-Layer Monochalcogenides" presents a comprehensive investigation of the large bulk photovoltaic effect (BPVE) in single-layer monochalcogenides, specifically focusing on Ge and Sn variants. These materials have attracted attention due to their promising optical properties and lack of inversion symmetry in the single-layer form, enabling spontaneous polarization and substantial BPVE.

The authors employ a first-principles density functional theory (DFT) approach to analyze the shift current and linear absorption under uniform illumination. Their findings indicate strong absorption within the visible spectrum and a notably high effective three-dimensional shift current (~100 µA/V$^2$). This value markedly surpasses those observed in other polar materials, positioning monochalcogenides as potential candidates for advanced optoelectronic applications.

Key Numerical Results

• Absorption and Polar Optical Response: The paper highlights significant absorption in the visible spectrum, laying the groundwork for potential applications in solar energy and photodetection technologies. The large effective three-dimensional shift current (approximately 100 µA/V$^2$) stands out, suggesting monochalcogenides could offer enhanced performance compared to current photovoltaic materials.
• Spontaneous Polarization: The integral of the shift-current tensor correlates strongly with the effective three-dimensional electric polarization (~1.9 C/m$^2$). This alignment confirms the intrinsic polarization properties of single-layer monochalcogenides, which are conducive to maximizing the BPVE.

Implications and Future Prospects

The paper's findings suggest that monochalcogenides, with their strong optical absorption and pronounced BPVE, could be crucial in developing polar optoelectronic devices. The correlation between shift current and spontaneous polarization underscores the potential to tailor these properties through material design and external electric fields.

From a theoretical perspective, the use of a Rice-Mele tight-binding model guides understanding the shift-current response in these materials. It provides insights into polarization dependence and suggests implications for broader classes of noncentrosymmetric materials.

Speculation on Future Developments

Advancements in AI and computational methods could further refine the theoretical models used to predict and analyze the BPVE in monochalcogenides. As AI continues to evolve, it may assist in discovering new materials or predicting the optoelectronic behavior of complex systems under various environmental conditions. Furthermore, continued research and development could lead to enhanced fabrication techniques, broadening the applicability and integration of monochalcogenides into next-generation electronic and photonic devices.

In conclusion, the paper thoroughly explores the promising attributes of single-layer monochalcogenides, and their practical and theoretical relevance in polar material research. By articulating the nuanced relationship between spontaneous polarization and the BPVE, the paper lays essential theoretical groundwork for advancing optoelectronic technologies.