J. C. Rodriguez E., H. Grisk, A. Anadón, H. Singh, G. Malinowski, M. Hehn, J. Curiale, J. Gorchon
Magnetic imaging techniques are widespread critical tools used in fields such as magnetism, spintronics, or even superconductivity. Among them, one of the most versatile methods is the magneto-optical Kerr effect. However, as soon as light is blocked from interacting with the magnetic layer, such as in deeply buried layers, optical techniques become ineffective. In this work, we present a spin accumulation based magneto-optical Kerr effect microscopy technique that enables imaging of a magnetic thin-film covered by thick and opaque metallic layers. The technique is based on the generation and detection of transient spin accumulations that propagate through the thick metallic layer. These spin accumulation signals are directly triggered and detected optically on the same side, lifting any substrate transparency requirements. The spin accumulation signals detected on a Cu layer decay with a characteristic length of 60 nm, much longer than the 12 nm optical penetration depth, allowing for the detection of magnetic contrast with Cu capping layers up to hundreds of nm. This method should enable magnetic imaging in a wide range of experiments where the surface of interest is covered by electrodes.
{"title":"Spin accumulation based deep MOKE microscopy","authors":"J. C. Rodriguez E., H. Grisk, A. Anadón, H. Singh, G. Malinowski, M. Hehn, J. Curiale, J. Gorchon","doi":"10.1063/5.0312055","DOIUrl":"https://doi.org/10.1063/5.0312055","url":null,"abstract":"Magnetic imaging techniques are widespread critical tools used in fields such as magnetism, spintronics, or even superconductivity. Among them, one of the most versatile methods is the magneto-optical Kerr effect. However, as soon as light is blocked from interacting with the magnetic layer, such as in deeply buried layers, optical techniques become ineffective. In this work, we present a spin accumulation based magneto-optical Kerr effect microscopy technique that enables imaging of a magnetic thin-film covered by thick and opaque metallic layers. The technique is based on the generation and detection of transient spin accumulations that propagate through the thick metallic layer. These spin accumulation signals are directly triggered and detected optically on the same side, lifting any substrate transparency requirements. The spin accumulation signals detected on a Cu layer decay with a characteristic length of 60 nm, much longer than the 12 nm optical penetration depth, allowing for the detection of magnetic contrast with Cu capping layers up to hundreds of nm. This method should enable magnetic imaging in a wide range of experiments where the surface of interest is covered by electrodes.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"35 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yuan Yu, Jiaqi Liu, Rujun Zhang, Qingying Luo, Si Zheng, Shengnan Yuan, Yufeng Zhou, Hairong Zheng, Feiyan Cai
High-throughput and biocompatible acoustofluidic manipulation of living cells and microparticles is essential for applications in cellular medicine, tissue engineering, and drug screening. Conventional surface acoustic wave (SAW)–based devices have been widely adopted; however, their high operating frequencies limit throughput, and the conversion of SAWs into leaky bulk waves in liquids induces strong acoustic streaming that compromises manipulation stability. Here, we present a low-frequency acoustofluidic device that exploits non-leaky quasi-Scholte waves in a piezoelectric thin plate to achieve high-throughput, stable, two-dimensional manipulation of particles and cells. Numerical simulations and laser Doppler vibrometry measurements confirm robust excitation of the quasi-Scholte mode, revealing evanescent acoustic fields with strong vertical gradients and well-defined in-plane standing waves in liquid. Experiments with microparticles and in vitro cells further demonstrate stable one- and two-dimensional patterning over large areas while maintaining high cell viability. This quasi-Scholte-wave-based acoustofluidic platform provides a reliable, effective, and high-throughput approach for precise manipulation of cells and biomaterials.
{"title":"High-throughput cell manipulation using low-frequency quasi-Scholte wave-based acoustofluidics","authors":"Yuan Yu, Jiaqi Liu, Rujun Zhang, Qingying Luo, Si Zheng, Shengnan Yuan, Yufeng Zhou, Hairong Zheng, Feiyan Cai","doi":"10.1063/5.0307916","DOIUrl":"https://doi.org/10.1063/5.0307916","url":null,"abstract":"High-throughput and biocompatible acoustofluidic manipulation of living cells and microparticles is essential for applications in cellular medicine, tissue engineering, and drug screening. Conventional surface acoustic wave (SAW)–based devices have been widely adopted; however, their high operating frequencies limit throughput, and the conversion of SAWs into leaky bulk waves in liquids induces strong acoustic streaming that compromises manipulation stability. Here, we present a low-frequency acoustofluidic device that exploits non-leaky quasi-Scholte waves in a piezoelectric thin plate to achieve high-throughput, stable, two-dimensional manipulation of particles and cells. Numerical simulations and laser Doppler vibrometry measurements confirm robust excitation of the quasi-Scholte mode, revealing evanescent acoustic fields with strong vertical gradients and well-defined in-plane standing waves in liquid. Experiments with microparticles and in vitro cells further demonstrate stable one- and two-dimensional patterning over large areas while maintaining high cell viability. This quasi-Scholte-wave-based acoustofluidic platform provides a reliable, effective, and high-throughput approach for precise manipulation of cells and biomaterials.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"70 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Regrown nonalloyed ohmic contacts for AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated using low-temperature pulsed sputtering deposition (PSD) of highly Si-doped degenerate GaN (d-GaN) onto inductively coupled plasma-etched recesses. The regrown d-GaN (thickness: 250 nm) shows a sheet resistance of 7.2 Ω/sq. with a carrier concentration and mobility of 3.4×1020 cm−3 and 100 cm2 V−1 s−1, yielding a total contact resistance of 0.058±0.004 Ω mm. The inherent interface resistance between the PSD-regrown d-GaN and two-dimensional electron gas was estimated using the transfer length method to be 0.033±0.005 Ω mm, which is close to the single-interface quantum injection limit (0.026 Ω mm). The fabricated HEMT devices with 2 μm gate length exhibited good characteristics (maximum drain current density = 850 mA mm−1, maximum transconductance = 0.2 S mm−1, and on-resistance = 2.1 Ω mm). These results indicate that the low-temperature regrowth of nonalloyed d-GaN contacts with ultralow resistance using PSD is a scalable and low-thermal-budget route for future radio frequency transistors.
{"title":"Ultralow contact resistance of 0.058 Ω mm achieved by pulsed sputtering deposition of regrown degenerately doped GaN contacts for AlGaN/GaN high-electron-mobility transistors","authors":"Kohei Ueno, Kaito Fujisawa, Hiroshi Fujioka","doi":"10.1063/5.0311448","DOIUrl":"https://doi.org/10.1063/5.0311448","url":null,"abstract":"Regrown nonalloyed ohmic contacts for AlGaN/GaN high-electron-mobility transistors (HEMTs) were fabricated using low-temperature pulsed sputtering deposition (PSD) of highly Si-doped degenerate GaN (d-GaN) onto inductively coupled plasma-etched recesses. The regrown d-GaN (thickness: 250 nm) shows a sheet resistance of 7.2 Ω/sq. with a carrier concentration and mobility of 3.4×1020 cm−3 and 100 cm2 V−1 s−1, yielding a total contact resistance of 0.058±0.004 Ω mm. The inherent interface resistance between the PSD-regrown d-GaN and two-dimensional electron gas was estimated using the transfer length method to be 0.033±0.005 Ω mm, which is close to the single-interface quantum injection limit (0.026 Ω mm). The fabricated HEMT devices with 2 μm gate length exhibited good characteristics (maximum drain current density = 850 mA mm−1, maximum transconductance = 0.2 S mm−1, and on-resistance = 2.1 Ω mm). These results indicate that the low-temperature regrowth of nonalloyed d-GaN contacts with ultralow resistance using PSD is a scalable and low-thermal-budget route for future radio frequency transistors.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"36 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160565","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
High aspect ratio hole etching processes require high-speed etching of SiO2 and Si3N4 films. Cryogenic etching significantly increases the etch rates of these two films by lowering the substrate temperature. However, the etching behavior and mechanisms in the temperature range below −70 °C remain unclear. In this work, we investigate the etching behavior of blanket SiO2 films, from 25 to −200 °C, and examine the mechanisms through in situ analyses. Our results show that the etch rate at −100 °C is approximately 3.2 times higher than that at 25 °C, and is associated with the highest etching efficiency in our experiments. This enhancement in the etch rate is attributed to the co-adsorption of H2O and HF, which increases the number of etchants on the SiO2 surface. At temperatures lower than −100 °C, the solidification of H2O reduces the co-adsorption of HF, decreasing the etch rate. At temperatures below −150 °C, the etch rate declines further, owing to the reduced volatility of the reaction product SiF4. These findings provide valuable insights for optimizing etching processes under cryogenic conditions.
{"title":"In situ analysis of SiO2 films etched under cryogenic conditions using H2/F2/Ar gas mixture plasma","authors":"Yuma Kato, Junji Kataoka, Ryo Saito, Daiki Iino, Kazuaki Kurihara, Tetsuya Sato, Hiroyuki Fukumizu","doi":"10.1063/5.0303879","DOIUrl":"https://doi.org/10.1063/5.0303879","url":null,"abstract":"High aspect ratio hole etching processes require high-speed etching of SiO2 and Si3N4 films. Cryogenic etching significantly increases the etch rates of these two films by lowering the substrate temperature. However, the etching behavior and mechanisms in the temperature range below −70 °C remain unclear. In this work, we investigate the etching behavior of blanket SiO2 films, from 25 to −200 °C, and examine the mechanisms through in situ analyses. Our results show that the etch rate at −100 °C is approximately 3.2 times higher than that at 25 °C, and is associated with the highest etching efficiency in our experiments. This enhancement in the etch rate is attributed to the co-adsorption of H2O and HF, which increases the number of etchants on the SiO2 surface. At temperatures lower than −100 °C, the solidification of H2O reduces the co-adsorption of HF, decreasing the etch rate. At temperatures below −150 °C, the etch rate declines further, owing to the reduced volatility of the reaction product SiF4. These findings provide valuable insights for optimizing etching processes under cryogenic conditions.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"224 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
ScAlN is a III-nitride ferroelectric material that has attracted considerable interest for its large remanent polarization, high thermal stability, and compatibility with GaN-based device platforms, and its properties strongly depend on growth conditions. In this study, ScAlN films were grown on Si-doped n-GaN/AlN/sapphire substrates by sputter epitaxy at growth temperatures of 420–675 °C, and their structural and ferroelectric characteristics were systematically investigated. X-ray diffraction and reciprocal space mapping revealed that the a-axis lattice constant increased, but the c-axis lattice constant simultaneously decreased, at growth temperatures above approximately 650 °C, indicating a temperature-induced modification of the ScAlN lattice. Positive-up–negative-down measurements showed a significant leakage current at temperatures above 550 °C, which prevented the saturation of the remanent polarization in the polarization–electric field characteristics. At lower growth temperatures, the films exhibited remanent polarization and coercive fields comparable to those reported for high-quality ScAlN films grown on GaN by molecular-beam epitaxy and metalorganic chemical vapor deposition. This result demonstrates that low-temperature sputter epitaxy can reproduce the intrinsic ferroelectric switching behavior of ScAlN. Thus, low-temperature sputter epitaxy effectively suppresses the leakage current and enables reliable ferroelectric switching, providing useful guidelines for optimizing ScAlN deposition processes for ferroelectric device applications.
{"title":"Structural and ferroelectric properties of sputter-epitaxial ScAlN on GaN grown at various temperatures","authors":"Sawaki Sato, Yusuke Wakamoto, Takuya Maeda, Hiroshi Funakubo, Kohei Ueno, Hiroshi Fujioka, Kazuhisa Ikeda, Atsushi Kobayashi","doi":"10.1063/5.0313954","DOIUrl":"https://doi.org/10.1063/5.0313954","url":null,"abstract":"ScAlN is a III-nitride ferroelectric material that has attracted considerable interest for its large remanent polarization, high thermal stability, and compatibility with GaN-based device platforms, and its properties strongly depend on growth conditions. In this study, ScAlN films were grown on Si-doped n-GaN/AlN/sapphire substrates by sputter epitaxy at growth temperatures of 420–675 °C, and their structural and ferroelectric characteristics were systematically investigated. X-ray diffraction and reciprocal space mapping revealed that the a-axis lattice constant increased, but the c-axis lattice constant simultaneously decreased, at growth temperatures above approximately 650 °C, indicating a temperature-induced modification of the ScAlN lattice. Positive-up–negative-down measurements showed a significant leakage current at temperatures above 550 °C, which prevented the saturation of the remanent polarization in the polarization–electric field characteristics. At lower growth temperatures, the films exhibited remanent polarization and coercive fields comparable to those reported for high-quality ScAlN films grown on GaN by molecular-beam epitaxy and metalorganic chemical vapor deposition. This result demonstrates that low-temperature sputter epitaxy can reproduce the intrinsic ferroelectric switching behavior of ScAlN. Thus, low-temperature sputter epitaxy effectively suppresses the leakage current and enables reliable ferroelectric switching, providing useful guidelines for optimizing ScAlN deposition processes for ferroelectric device applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"4 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ze Yan, Quanzhi Zhang, Jianrong Zhang, Li Xi, Wenbo Sui, Desheng Xue, Dezheng Yang
Understanding the interconversion between charge current and spin current in antiferromagnetic materials is crucial for advancing antiferromagnetic spintronic devices. In this work, we utilize the second harmonic technique and the spin Hall magnetoresistance method to investigate the spin current generation in Mn3Ir/Co bilayers. The angular dependence of the second harmonic Hall voltage shows that only a y-polarized spin current is generated, which exerts spin–orbit torques on Co magnetic moments. Contrary to the positive spin Hall magnetoresistance induced by y-polarized spin current, we observe the anomalous negative spin Hall magnetoresistance in Mn3Ir/Co bilayers. By further investigating the Mn3Ir thickness dependence of the negative spin Hall magnetoresistance and spin–orbit torque, we demonstrate that the negative spin Hall magnetoresistance originates from the interconversion between charge current and spin current driven by interfacial spin–orbit coupling. Our findings provide compelling evidence for interfacial spin–orbit coupling conversion at the antiferromagnetic/ferromagnetic bilayer interface. This indicates that the interface engineering is essential for optimizing noncollinear antiferromagnetic spintronic devices.
{"title":"Negative spin Hall magnetoresistance in Mn3Ir/Co bilayers induced by interfacial spin-orbit coupling","authors":"Ze Yan, Quanzhi Zhang, Jianrong Zhang, Li Xi, Wenbo Sui, Desheng Xue, Dezheng Yang","doi":"10.1063/5.0294519","DOIUrl":"https://doi.org/10.1063/5.0294519","url":null,"abstract":"Understanding the interconversion between charge current and spin current in antiferromagnetic materials is crucial for advancing antiferromagnetic spintronic devices. In this work, we utilize the second harmonic technique and the spin Hall magnetoresistance method to investigate the spin current generation in Mn3Ir/Co bilayers. The angular dependence of the second harmonic Hall voltage shows that only a y-polarized spin current is generated, which exerts spin–orbit torques on Co magnetic moments. Contrary to the positive spin Hall magnetoresistance induced by y-polarized spin current, we observe the anomalous negative spin Hall magnetoresistance in Mn3Ir/Co bilayers. By further investigating the Mn3Ir thickness dependence of the negative spin Hall magnetoresistance and spin–orbit torque, we demonstrate that the negative spin Hall magnetoresistance originates from the interconversion between charge current and spin current driven by interfacial spin–orbit coupling. Our findings provide compelling evidence for interfacial spin–orbit coupling conversion at the antiferromagnetic/ferromagnetic bilayer interface. This indicates that the interface engineering is essential for optimizing noncollinear antiferromagnetic spintronic devices.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"28 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160129","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hang Shi, Yuqian Jiang, Yuping Tian, Wenpeng Wang, Shaozhi Li, Wei-Jiang Gong, Xiangru Kong
Two-dimensional altermagnets have recently gained attention for enabling spin-polarized transport without net magnetization. The van der Waals layered form introduces an additional layer degree of freedom, allowing new ways to control spin and valley behaviors through interlayer coupling and external modulation. In our work, bilayer Nb2SeTeO shows tunable magnetic and topological properties based on first-principles calculations. The stacking configuration strongly influences its electronic structure and spin–valley characteristics. External electric fields and strain effectively modulate these properties. Compressive biaxial strain drives a transition to a quantum spin Hall phase with a high spin Chern number, while compressive uniaxial strain induces a quantum layer spin Hall effect, where chiral edge states can be switched by applying uniaxial strain in two vertical directions. These results identify bilayer Nb2SeTeO as a promising material for spintronic devices with controllable topological phases.
{"title":"Tunable quantum layer spin Hall effect in bilayer altermagnetic Nb2SeTeO","authors":"Hang Shi, Yuqian Jiang, Yuping Tian, Wenpeng Wang, Shaozhi Li, Wei-Jiang Gong, Xiangru Kong","doi":"10.1063/5.0312073","DOIUrl":"https://doi.org/10.1063/5.0312073","url":null,"abstract":"Two-dimensional altermagnets have recently gained attention for enabling spin-polarized transport without net magnetization. The van der Waals layered form introduces an additional layer degree of freedom, allowing new ways to control spin and valley behaviors through interlayer coupling and external modulation. In our work, bilayer Nb2SeTeO shows tunable magnetic and topological properties based on first-principles calculations. The stacking configuration strongly influences its electronic structure and spin–valley characteristics. External electric fields and strain effectively modulate these properties. Compressive biaxial strain drives a transition to a quantum spin Hall phase with a high spin Chern number, while compressive uniaxial strain induces a quantum layer spin Hall effect, where chiral edge states can be switched by applying uniaxial strain in two vertical directions. These results identify bilayer Nb2SeTeO as a promising material for spintronic devices with controllable topological phases.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"37 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Przemysław Przybysz, Karma Tenzin, Berkay Kilic, Witold Kozłowski, Paweł J. Kowalczyk, Paweł Dabrowski, Jagoda Sławińska
Crystal symmetries in solids give rise to spin–momentum locking, which determines how an electron's spin orientation depends on its momentum. This relationship, often referred to as spin texture, influences both charge-to-spin conversion and spin relaxation, making it one of the essential characteristics for spin–orbit-driven phenomena. Materials with strong spin–orbit coupling and broken inversion symmetry can host persistent spin textures (PSTs)—unidirectional spin configurations in momentum space, supporting efficient charge-to-spin conversion and extended spin lifetimes. Monolayer WTe2, a topological material crystallizing in a rectangular lattice, is a notable example; its symmetry enforces a canted PST, enabling the quantum spin Hall effect with the nontrivial spin orientation. Here, we use first-principles calculations to explore how these properties are modified when WTe2 is interfaced with graphene. We find that the PST is preserved by the local symmetry present in different regions of the heterostructure, while the system develops extended electron and hole pockets, resulting in semimetallic behavior. Although the bandgap closes and eliminates the quantum spin Hall phase, spin Hall effects remain robust in both conventional and unconventional geometries. The computed spin Hall conductivities are comparable to those of other two-dimensional materials, and the survival of the PST suggests the possibility of long-range spin transport even in the absence of topological edge states. In addition, the graphene layer serves as an oxidation barrier, helping protect the intrinsic properties of WTe2 and supporting the potential of this heterostructure for spintronic applications.
{"title":"Persistent spin texture protected by the approximate symmetry in a weakly interacting graphene/WTe2 heterostructure","authors":"Przemysław Przybysz, Karma Tenzin, Berkay Kilic, Witold Kozłowski, Paweł J. Kowalczyk, Paweł Dabrowski, Jagoda Sławińska","doi":"10.1063/5.0301803","DOIUrl":"https://doi.org/10.1063/5.0301803","url":null,"abstract":"Crystal symmetries in solids give rise to spin–momentum locking, which determines how an electron's spin orientation depends on its momentum. This relationship, often referred to as spin texture, influences both charge-to-spin conversion and spin relaxation, making it one of the essential characteristics for spin–orbit-driven phenomena. Materials with strong spin–orbit coupling and broken inversion symmetry can host persistent spin textures (PSTs)—unidirectional spin configurations in momentum space, supporting efficient charge-to-spin conversion and extended spin lifetimes. Monolayer WTe2, a topological material crystallizing in a rectangular lattice, is a notable example; its symmetry enforces a canted PST, enabling the quantum spin Hall effect with the nontrivial spin orientation. Here, we use first-principles calculations to explore how these properties are modified when WTe2 is interfaced with graphene. We find that the PST is preserved by the local symmetry present in different regions of the heterostructure, while the system develops extended electron and hole pockets, resulting in semimetallic behavior. Although the bandgap closes and eliminates the quantum spin Hall phase, spin Hall effects remain robust in both conventional and unconventional geometries. The computed spin Hall conductivities are comparable to those of other two-dimensional materials, and the survival of the PST suggests the possibility of long-range spin transport even in the absence of topological edge states. In addition, the graphene layer serves as an oxidation barrier, helping protect the intrinsic properties of WTe2 and supporting the potential of this heterostructure for spintronic applications.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"157 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146161045","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Srinivasa Rao Konda, Puspendu Barik, Sushma Kumari, Subhash Singh, Venkatesh Mottamchetty, Amit Srivasthava, Vyacheslav V. Kim, Rashid A. Ganeev, Venugopal Rao Soma, Chunlei Guo, Wei Li
Engineering nonlinear optical responses in two-dimensional materials via heterostructure design is emerging as a powerful approach for next-generation photonic devices. Although perturbative nonlinear effects in these systems are well studied, their connection to nonperturbative processes such as high-harmonic generation (HHG) remains largely unexplored. Here, we investigate the HHG from few-layer MoS2 nanosheets integrated with CdSe and passivated CdSe/V2O5 quantum dots (QDs). The hybrid structures exhibit pronounced enhancement in harmonic intensity and a clear extension of the harmonic cutoff relative to pristine MoS2. We demonstrate that interfacial charge-transfer dynamics—previously associated with the dominant contribution to the third-order susceptibility χ(3)—also govern the efficiency of HHG, thereby establishing a direct link between perturbative and nonperturbative regimes in these 0D–2D hybrids. The carrier injection from the QDs increases the electron–hole population participating in HHG, while the moderated response in passivated QD systems highlights the role of interfacial potential barriers. These results provide a unified physical picture of nonlinear optical processes in hybrid nanostructures and offer design principles for enhancing coherent light generation.
{"title":"High-order harmonics generation in MoS2 nanosheets in the presence of CdSe and CdSe/V2O5 quantum dots","authors":"Srinivasa Rao Konda, Puspendu Barik, Sushma Kumari, Subhash Singh, Venkatesh Mottamchetty, Amit Srivasthava, Vyacheslav V. Kim, Rashid A. Ganeev, Venugopal Rao Soma, Chunlei Guo, Wei Li","doi":"10.1063/5.0313492","DOIUrl":"https://doi.org/10.1063/5.0313492","url":null,"abstract":"Engineering nonlinear optical responses in two-dimensional materials via heterostructure design is emerging as a powerful approach for next-generation photonic devices. Although perturbative nonlinear effects in these systems are well studied, their connection to nonperturbative processes such as high-harmonic generation (HHG) remains largely unexplored. Here, we investigate the HHG from few-layer MoS2 nanosheets integrated with CdSe and passivated CdSe/V2O5 quantum dots (QDs). The hybrid structures exhibit pronounced enhancement in harmonic intensity and a clear extension of the harmonic cutoff relative to pristine MoS2. We demonstrate that interfacial charge-transfer dynamics—previously associated with the dominant contribution to the third-order susceptibility χ(3)—also govern the efficiency of HHG, thereby establishing a direct link between perturbative and nonperturbative regimes in these 0D–2D hybrids. The carrier injection from the QDs increases the electron–hole population participating in HHG, while the moderated response in passivated QD systems highlights the role of interfacial potential barriers. These results provide a unified physical picture of nonlinear optical processes in hybrid nanostructures and offer design principles for enhancing coherent light generation.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"15 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146161115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anda Cheng, Haoxuan Yang, Lujing Wang, Changzheng Sun, Zhibiao Hao, Bing Xiong, Yanjun Han, Jian Wang, Hongtao Li, Lin Gan, Yi Luo, Lai Wang
InGaN red light-emitting diode (LED) has attracted increasing interest in recent years due to its important role in full-color micro-LED displays. Covering an AlGaN capping layer on top of a high-indium-composition InGaN quantum well can improve the performance of an InGaN red LED, which is considered to compensate for stress and suppress the decomposition of InN. However, the AlGaN capping layer can also cause changes in the polarization electric field, which have been almost overlooked in previous studies. In this work, theoretical simulations reveal that the polarization effect of the AlGaN capping layer necessitates a trade-off between the long wavelength and high luminous intensity of InGaN red LEDs, thereby yielding an optimal Al composition of 0.4. Meanwhile, experimental results demonstrate that the micro-LED with an Al composition of 0.4 in the capping layer exhibits the most uniform luminescence. The underlying reason for this optimal luminous uniformity is elucidated by stress engineering via time-of-flight secondary ion mass spectrometry characterization, which verifies the in-plane uniformity of the indium composition within the quantum wells—a feature not addressed in previous research. The 30 × 30 μm2 micro-scale light-emitting diode achieves the longest emission wavelength of ∼650 nm and the highest on-wafer external quantum efficiency of 1.8%, which further corroborates the theoretical simulation results.
{"title":"Achieving high-efficiency, long-wavelength, and high-uniformity InGaN red micro-LEDs through polarization effect and stress engineering of the AlGaN capping layer","authors":"Anda Cheng, Haoxuan Yang, Lujing Wang, Changzheng Sun, Zhibiao Hao, Bing Xiong, Yanjun Han, Jian Wang, Hongtao Li, Lin Gan, Yi Luo, Lai Wang","doi":"10.1063/5.0312640","DOIUrl":"https://doi.org/10.1063/5.0312640","url":null,"abstract":"InGaN red light-emitting diode (LED) has attracted increasing interest in recent years due to its important role in full-color micro-LED displays. Covering an AlGaN capping layer on top of a high-indium-composition InGaN quantum well can improve the performance of an InGaN red LED, which is considered to compensate for stress and suppress the decomposition of InN. However, the AlGaN capping layer can also cause changes in the polarization electric field, which have been almost overlooked in previous studies. In this work, theoretical simulations reveal that the polarization effect of the AlGaN capping layer necessitates a trade-off between the long wavelength and high luminous intensity of InGaN red LEDs, thereby yielding an optimal Al composition of 0.4. Meanwhile, experimental results demonstrate that the micro-LED with an Al composition of 0.4 in the capping layer exhibits the most uniform luminescence. The underlying reason for this optimal luminous uniformity is elucidated by stress engineering via time-of-flight secondary ion mass spectrometry characterization, which verifies the in-plane uniformity of the indium composition within the quantum wells—a feature not addressed in previous research. The 30 × 30 μm2 micro-scale light-emitting diode achieves the longest emission wavelength of ∼650 nm and the highest on-wafer external quantum efficiency of 1.8%, which further corroborates the theoretical simulation results.","PeriodicalId":8094,"journal":{"name":"Applied Physics Letters","volume":"98 1","pages":""},"PeriodicalIF":4.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146160123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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