Switchable Enhanced Spin Photocurrent in Rashba and Cubic Dresselhaus Ferroelectric Semiconductors

Manipulating Photogalvanic Effects in Two-Dimensional Multiferroic Breathing Kagome Materials

Multiferroic materials, known for their multiple tunable orders, present an exceptional opportunity to manipulate nonlinear optical responses that are sensitive to symmetry. In this study, we propose leveraging electric and magnetic fields to selectively control and switch specific types of photogalvanic effects in two-dimensional multiferroic breathing kagome materials. Taking monolayer Nb3I8 as an example, we demonstrate that the shift current, characterized by the real-space shift of electrons and holes, is predominantly unaffected by magnetic order. In contrast, injection current, featured by quantum metric dipole in momentum space, is closely related to valley polarization, which can be controlled by a magnetic field. Furthermore, both photocurrents can be reversed by an out-of-plane electric field via lattice breathing. Our findings reveal the potential of multiferroic breathing kagome structures for multifunctional optoelectronic applications and sensors.

Enormous and Tunable Bulk Charge/Spin Photovoltaic Effect in Piezoelectric Binary Materials T-IV-VI and T-V-V

Understanding the nonlinear response of light and materials is crucial for fundamental physics and next-generation electronic devices. In this work, we have investigated the second-order nonlinear bulk photovoltaic (BPV) and bulk spin photovoltaic (BSPV) effects in the piezoelectric binary materials T-IV-VI and T-V-V (IV = Ge, Sn; VI = S, Se; and V = P, As, Sb, Bi). The independent nonzero conductivity tensors of charge current are derived for these binaries through the symmetry analysis, along with the mechanism for generating pure spin current. These binaries, with their unique folded structure, exhibit significant charge and spin currents under illumination. Furthermore, we find that strain engineering can effectively modulate charge/spin currents by influencing charge density distribution and built-in electric field due to the piezoelectric effect. Our research suggests that the piezoelectric binary materials possess enormous and tunable charge/spin currents, underscoring their potential for applications in nonlinear flexible optoelectronics and spintronics.

Anisotropic Nonlocal Damping in Ferromagnet/α-GeTe Bilayers Enabled by Splitting Energy Bands

The understanding and manipulation of anisotropic Gilbert damping is crucial for both fundamental research and versatile engineering and optimization. Although several works on anisotropic damping have been reported, no direct relationship between the band structure and anisotropic damping was established. Here, we observed an anisotropic damping in Fe/GeTe manipulated by the symmetric band structures of GeTe via angle-resolved photoemission spectroscopy. Moreover, the anisotropic damping can be modified by the symmetry of band structures. Our Letter provides insightful understandings of the anisotropic Gilbert damping in ferromagnets interfaced with Rashba semiconductors and suggests the possibility of manipulating the Gilbert damping by band engineering.

Gate Dielectrics Integration for 2D Electronics: Challenges, Advances, and Outlook

2D semiconductors have emerged both as an ideal platform for fundamental studies and as promising channel materials in beyond-silicon field-effect-transistors due to their outstanding electrical properties and exceptional tunability via external field. However, the lack of proper dielectrics for 2D semiconductors has become a major roadblock for their further development toward practical applications. The prominent issues between conventional 3D dielectrics and 2D semiconductors arise from the integration and interface quality, where defect states and imperfections lead to dramatic deterioration of device performance. In this review article, the root causes of such issues are briefly analyzed and recent advances on some possible solutions, including various approaches of adapting conventional dielectrics to 2D semiconductors, and the development of novel dielectrics with van der Waals surface toward high-performance 2D electronics are summarized. Then, in the perspective, the requirements of ideal dielectrics for state-of-the-art 2D devices are outlined and an outlook for their future development is provided.

Electric field induced pure spin-photo current in zigzag stanene and germanene nanoribbons

The spin-photo current in single layer stanene and germanene under a linearly polarized light is theoretically investigated based on the tight-binding Hamiltonian combined with the nonequilibrium Green’s function at room temperature. The results show that by considering the simultaneous effect of the linear illumination and a vertical external electric field without any magnetic exchange element, pure spin-photo current without charge current is generated in two-dimensional lattices with a large intrinsic spin–orbit coupling. The necessity of enhanced spin life-time for detection of spin polarization can be explained by spin-valley locking concept. Spin-valley locking arises in buckled two-dimensional materials as a result of the large spin–orbit coupling and electric-field reversible valley spin polarization. Equal absorption of the linearly illumination at both valleys with different spin polarization, leads to pure spin-photo current injection. In addition, an acceptable photoresponsivity has been reported in a broad range of photon energy. The numerical results indicate high quantum efficiency with a maximum of nearly 83% and 50% for stanene and germanene, respectively. This work may pave theoretical reference toward design of new spin-optoelectronic devices based on satanene and germanene junctions with high performance.