Pub Date : 2023-08-22DOI: 10.1038/s41699-023-00420-1
Frank Volmer, Manfred Ersfeld, Paulo E. Faria Junior, Lutz Waldecker, Bharti Parashar, Lars Rathmann, Sudipta Dubey, Iulia Cojocariu, Vitaliy Feyer, Kenji Watanabe, Takashi Taniguchi, Claus M. Schneider, Lukasz Plucinski, Christoph Stampfer, Jaroslav Fabian, Bernd Beschoten
Transition metal dichalcogenides (TMDs) have attracted much attention in the fields of valley- and spintronics due to their property of forming valley-polarized excitons when illuminated by circularly polarized light. In TMD-heterostructures it was shown that these electron-hole pairs can scatter into valley-polarized interlayer exciton states, which exhibit long lifetimes and a twist-angle dependence. However, the question how to create a valley polarization of free charge carriers in these heterostructures after a valley selective optical excitation is unexplored, despite its relevance for opto-electronic devices. Here, we identify an interlayer transfer mechanism in twisted WSe2/MoSe2 heterobilayers that transfers the valley polarization from excitons in WSe2 to free charge carriers in MoSe2 with valley lifetimes of up to 12 ns. This mechanism is most efficient at large twist angles, whereas the valley lifetimes of free charge carriers are surprisingly short for small twist angles, despite the occurrence of interlayer excitons.
{"title":"Twist angle dependent interlayer transfer of valley polarization from excitons to free charge carriers in WSe2/MoSe2 heterobilayers","authors":"Frank Volmer, Manfred Ersfeld, Paulo E. Faria Junior, Lutz Waldecker, Bharti Parashar, Lars Rathmann, Sudipta Dubey, Iulia Cojocariu, Vitaliy Feyer, Kenji Watanabe, Takashi Taniguchi, Claus M. Schneider, Lukasz Plucinski, Christoph Stampfer, Jaroslav Fabian, Bernd Beschoten","doi":"10.1038/s41699-023-00420-1","DOIUrl":"10.1038/s41699-023-00420-1","url":null,"abstract":"Transition metal dichalcogenides (TMDs) have attracted much attention in the fields of valley- and spintronics due to their property of forming valley-polarized excitons when illuminated by circularly polarized light. In TMD-heterostructures it was shown that these electron-hole pairs can scatter into valley-polarized interlayer exciton states, which exhibit long lifetimes and a twist-angle dependence. However, the question how to create a valley polarization of free charge carriers in these heterostructures after a valley selective optical excitation is unexplored, despite its relevance for opto-electronic devices. Here, we identify an interlayer transfer mechanism in twisted WSe2/MoSe2 heterobilayers that transfers the valley polarization from excitons in WSe2 to free charge carriers in MoSe2 with valley lifetimes of up to 12 ns. This mechanism is most efficient at large twist angles, whereas the valley lifetimes of free charge carriers are surprisingly short for small twist angles, despite the occurrence of interlayer excitons.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-10"},"PeriodicalIF":9.7,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00420-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42744886","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-21DOI: 10.1038/s41699-023-00419-8
R. Muñoz, E. López-Elvira, C. Munuera, F. Carrascoso, Y. Xie, O. Çakıroğlu, T. Pucher, S. Puebla, A. Castellanos-Gomez, M. García-Hernández
We report on outstanding photo-responsivity, R > 103 A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS2 photodetectors. Our devices are based on the deterministic transfer of MoS2 on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C2H2/H2 gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.
我们报告了两个终端石墨烯/MoS2 光电探测器出色的光响应率 R > 103 A/W、快速响应（约 0.1 秒）以及从紫外到近红外的宽带灵敏度。我们的器件基于在蓝宝石上直接生长的石墨烯顶部确定性地转移 MoS2，其性能优于以前使用大规模生长的石墨烯的类似光电探测器。在此，我们设计了一套方案，利用等离子体辅助化学气相沉积（CVD）技术和 C2H2/H2 混合气体，在 700 °C 温度下在蓝宝石上直接生长出透明（透光率，Tr > 90%）、高导电性（片状电阻，R□ < 1 kΩ）、均匀且连续的石墨烯薄膜。我们的研究表明，等离子体辅助低温化学气相沉积技术可成功地在绝缘体上直接生长石墨烯，用于光电应用。
{"title":"Low T direct plasma assisted growth of graphene on sapphire and its integration in graphene/MoS2 heterostructure-based photodetectors","authors":"R. Muñoz, E. López-Elvira, C. Munuera, F. Carrascoso, Y. Xie, O. Çakıroğlu, T. Pucher, S. Puebla, A. Castellanos-Gomez, M. García-Hernández","doi":"10.1038/s41699-023-00419-8","DOIUrl":"10.1038/s41699-023-00419-8","url":null,"abstract":"We report on outstanding photo-responsivity, R > 103 A/W, fast response (~0.1 s), and broadband sensitivity ranging from the UV to the NIR in two terminal graphene/MoS2 photodetectors. Our devices are based on the deterministic transfer of MoS2 on top of directly grown graphene on sapphire, and their performance outperforms previous similar photodetectors using large-scale grown graphene. Here we devise a protocol for the direct growth of transparent (transmittance, Tr > 90%), highly conductive (sheet resistance, R□ < 1 kΩ) uniform and continuous graphene films on sapphire at 700 °C by using plasma-assisted chemical vapor deposition (CVD) with C2H2/H2 gas mixtures. Our study demonstrates the successful use of plasma-assisted low-temperature CVD techniques to directly grow graphene on insulators for optoelectronic applications.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-11"},"PeriodicalIF":9.7,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00419-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43494535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-21DOI: 10.1038/s41699-023-00417-w
Hector Iturriaga, Luis M. Martinez, Thuc T. Mai, Adam J. Biacchi, Mathias Augustin, Angela R. Hight Walker, Mohamed Fathi Sanad, Sreeprasad T. Sreenivasan, Yu Liu, Elton J. G. Santos, Cedomir Petrovic, Srinivasa R. Singamaneni
Among several well-known transition metal-based compounds, cleavable van der Waals (vdW) Fe3-xGeTe2 (FGT) magnet is a strong candidate for use in two-dimensional (2D) magnetic devices due to its strong perpendicular magnetic anisotropy, sizeable Curie temperature (TC ~154 K), and versatile magnetic character that is retained in the low-dimensional limit. While the TC remains far too low for practical applications, there has been a successful push toward improving it via external driving forces such as pressure, irradiation, and doping. Here we present experimental evidence of a room temperature (RT) ferromagnetic phase induced by the electrochemical intercalation of common tetrabutylammonium cations (TBA+) into quasi-2D FGT. We obtained Curie temperatures as high as 350 K with chemical and physical stability of the intercalated compound. The temperature-dependent Raman measurements, in combination with vdW-corrected ab initio calculations, suggest that charge transfer (electron doping) upon intercalation could lead to the observation of RT ferromagnetism. This work demonstrates that molecular intercalation is a viable route in realizing high-temperature vdW magnets in an inexpensive and reliable manner, and has the potential to be extended to bilayer and few-layer vdW magnets.
在几种众所周知的过渡金属基化合物中，可裂解范德华（vdW）Fe3-xGeTe2（FGT）磁体因其强大的垂直磁各向异性、可观的居里温度（TC ~154 K）以及在低维极限下保持的多功能磁性，成为二维（2D）磁性器件的有力候选材料。虽然居里温度对于实际应用来说仍然太低，但人们已经成功地通过压力、辐照和掺杂等外部驱动力来提高居里温度。在此，我们通过实验证明了普通四丁基铵阳离子（TBA+）电化学插层诱导的室温（RT）铁磁相进入准二维 FGT。我们获得了高达 350 K 的居里温度，并且插层化合物具有化学和物理稳定性。随温度变化的拉曼测量结果与 vdW 校正的 ab initio 计算相结合，表明插层时的电荷转移（电子掺杂）可导致 RT 铁磁性的观察。这项研究表明，分子插层是以廉价和可靠的方式实现高温 vdW 磁体的可行途径，并有可能扩展到双层和少层 vdW 磁体。
{"title":"Magnetic properties of intercalated quasi-2D Fe3-xGeTe2 van der Waals magnet","authors":"Hector Iturriaga, Luis M. Martinez, Thuc T. Mai, Adam J. Biacchi, Mathias Augustin, Angela R. Hight Walker, Mohamed Fathi Sanad, Sreeprasad T. Sreenivasan, Yu Liu, Elton J. G. Santos, Cedomir Petrovic, Srinivasa R. Singamaneni","doi":"10.1038/s41699-023-00417-w","DOIUrl":"10.1038/s41699-023-00417-w","url":null,"abstract":"Among several well-known transition metal-based compounds, cleavable van der Waals (vdW) Fe3-xGeTe2 (FGT) magnet is a strong candidate for use in two-dimensional (2D) magnetic devices due to its strong perpendicular magnetic anisotropy, sizeable Curie temperature (TC ~154 K), and versatile magnetic character that is retained in the low-dimensional limit. While the TC remains far too low for practical applications, there has been a successful push toward improving it via external driving forces such as pressure, irradiation, and doping. Here we present experimental evidence of a room temperature (RT) ferromagnetic phase induced by the electrochemical intercalation of common tetrabutylammonium cations (TBA+) into quasi-2D FGT. We obtained Curie temperatures as high as 350 K with chemical and physical stability of the intercalated compound. The temperature-dependent Raman measurements, in combination with vdW-corrected ab initio calculations, suggest that charge transfer (electron doping) upon intercalation could lead to the observation of RT ferromagnetism. This work demonstrates that molecular intercalation is a viable route in realizing high-temperature vdW magnets in an inexpensive and reliable manner, and has the potential to be extended to bilayer and few-layer vdW magnets.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-8"},"PeriodicalIF":9.7,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00417-w.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"57548917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
After the discovery of sp2-hybridized graphene and even lighter borophene, the scientific quest for the thinnest metallic sheets prompts the discovery of beryllene. As beryllium lacks p-electrons, the hybridization and structural evolution of beryllene in determining electronic/excitonic behaviors are scientifically interesting. Herein, we report the experimental realization of freestanding flat beryllene sheets with a lateral dimension of ~0.2–4 μm via sonochemical exfoliation. High-resolution transmission electron microscopy establishes the existence of hexagonal, square and stripe crystallographic phases. While characteristic Raman fingerprints ~451 and ~614 cm−1, and experimentally observed electrically metallic nature of beryllene (vindicated by density-functional-theory band structure calculations) establish beryllene synthesis. Room temperature magnetism in Be-G and Be-CNT hybrids (established by Raman mapping and magnetic force microscopic imaging) is an interesting finding. Beryllene was explored as a surface-enhanced Raman spectroscopy (SERS) anchor in molecular sensing, oxidation-resistant, and fire-resistant laminates. It is believed that the discovery of beryllene will lead to novel functionalities and emerging applications.
{"title":"Beryllene, the lightest Xene","authors":"Sumit Chahal, Arkamita Bandyopadhyay, Chan-Shan Yang, Prashant Kumar","doi":"10.1038/s41699-023-00415-y","DOIUrl":"10.1038/s41699-023-00415-y","url":null,"abstract":"After the discovery of sp2-hybridized graphene and even lighter borophene, the scientific quest for the thinnest metallic sheets prompts the discovery of beryllene. As beryllium lacks p-electrons, the hybridization and structural evolution of beryllene in determining electronic/excitonic behaviors are scientifically interesting. Herein, we report the experimental realization of freestanding flat beryllene sheets with a lateral dimension of ~0.2–4 μm via sonochemical exfoliation. High-resolution transmission electron microscopy establishes the existence of hexagonal, square and stripe crystallographic phases. While characteristic Raman fingerprints ~451 and ~614 cm−1, and experimentally observed electrically metallic nature of beryllene (vindicated by density-functional-theory band structure calculations) establish beryllene synthesis. Room temperature magnetism in Be-G and Be-CNT hybrids (established by Raman mapping and magnetic force microscopic imaging) is an interesting finding. Beryllene was explored as a surface-enhanced Raman spectroscopy (SERS) anchor in molecular sensing, oxidation-resistant, and fire-resistant laminates. It is believed that the discovery of beryllene will lead to novel functionalities and emerging applications.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-13"},"PeriodicalIF":9.7,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00415-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45800774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-17DOI: 10.1038/s41699-023-00416-x
G. Cardenas-Chirivi, K. Vega-Bustos, H. Rojas-Páez, D. Silvera-Vega, J. Pazos, O. Herrera, M. A. Macías, C. Espejo, W. López-Pérez, J. A. Galvis, P. Giraldo-Gallo
The coexistence of multiple ferroic orders, i.e., multiferroicity, is a scarce property to be found in materials. Historically, this state has been found mainly in 3-dimensional complex oxides, but so far, this state has still been elusive for the most widely studied and characterized family of 2-dimensional compounds, the transition metal dichalcogenides. In this study, we report the experimental realization of multiferroic states in this family of materials, at room temperature, in bulk single crystals of Te-doped WSe2. We observe the coexistence of ferromagnetism and ferroelectricity, evidenced in the presence of magnetization and piezoresponse force microscopy hysteresis loops. These findings open the possibility of widening the use and study of van der Waals-based multifunctional devices for nanoelectronics and spintronics applications.
多种铁阶共存，即多铁性，是材料中的稀缺特性。从历史上看，这种状态主要出现在三维复合氧化物中，但迄今为止，对于研究最广泛、特征最明显的二维化合物家族--过渡金属二钙化物--来说，这种状态仍然难以捉摸。在本研究中，我们报告了在室温下，在掺杂了 Te 的 WSe2 体单晶中，通过实验实现了该系列材料中的多铁态。我们观察到铁磁性和铁电性共存，磁化和压电响应力显微镜滞后环的存在证明了这一点。这些发现为扩大基于范德华的多功能器件在纳米电子学和自旋电子学应用中的使用和研究提供了可能性。
{"title":"Room temperature multiferroicity in a transition metal dichalcogenide","authors":"G. Cardenas-Chirivi, K. Vega-Bustos, H. Rojas-Páez, D. Silvera-Vega, J. Pazos, O. Herrera, M. A. Macías, C. Espejo, W. López-Pérez, J. A. Galvis, P. Giraldo-Gallo","doi":"10.1038/s41699-023-00416-x","DOIUrl":"10.1038/s41699-023-00416-x","url":null,"abstract":"The coexistence of multiple ferroic orders, i.e., multiferroicity, is a scarce property to be found in materials. Historically, this state has been found mainly in 3-dimensional complex oxides, but so far, this state has still been elusive for the most widely studied and characterized family of 2-dimensional compounds, the transition metal dichalcogenides. In this study, we report the experimental realization of multiferroic states in this family of materials, at room temperature, in bulk single crystals of Te-doped WSe2. We observe the coexistence of ferromagnetism and ferroelectricity, evidenced in the presence of magnetization and piezoresponse force microscopy hysteresis loops. These findings open the possibility of widening the use and study of van der Waals-based multifunctional devices for nanoelectronics and spintronics applications.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-10"},"PeriodicalIF":9.7,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00416-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46561929","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-11DOI: 10.1038/s41699-023-00418-9
So-Yeon Yoo, Haena Yim, Ahrom Ryu, Chansoo Yoon, Bae Ho Park, Sahn Nahm, Ji-Won Choi
Solution-based processable high-k 2-dimensional (2D) ferroelectrics have attracted significant interest for use in next-generation nanoelectronics. Although few studies on potential 2D ferroelectric nanosheets in local areas have been conducted, reports on the thin-film characteristics applicable to the device are insufficient. In this study, we successfully synthesize high-k 2D Sr1.8Bi0.2Nan-3NbnO3n+1 (octahedral units, n = 3–5) nanosheets by the engineering of the n of NbO6 octahedral layers with A-site modification, and realized ferroelectric characteristics in ultrathin films (below 10 nm). The nanosheets are synthesized by a solution-based cation exchange process and deposited using the Langmuir-Blodgett (LB) method. As increasing the NbO6 octahedral layer, the thickness of the nanosheets increased and the band gaps are tuned to 3.80 eV (n = 3), 3.76 eV (n = 4), and 3.70 eV (n = 5). In addition, the dielectric permittivity of the 5-layer stacked nanofilm increase to 26 (n = 3), 33 (n = 4), and 62 (n = 5). In particular, the increased perovskite layer exhibits large distortions due to the size mismatch of Sr/Bi/Na ions at the A-site and promotes local ferroelectric instability due to its spontaneous polarization along the c-axis caused by an odd n number. We investigate the stable ferroelectricity in Pt/ 5-layer Sr1.8Bi0.2Na2Nb5O16 / Nb:STO capacitor by polarization-electric field (P-E) hysteresis; the coercive electric field (Ec) was 338 kV cm−1 and the remnant polarization (Pr) 2.36 μC cm−2. The ferroelectric properties of ultrathin 2D materials could drive interesting innovations in next-generation electronics.
基于溶液的可加工高 K 二维 (2D) 铁电材料在下一代纳米电子学中的应用引起了人们的极大兴趣。虽然对局部地区潜在的二维铁电纳米片进行了少量研究，但有关适用于该器件的薄膜特性的报道还不够充分。在本研究中，我们通过对 NbO6 八面体层的 n 进行 A 位修饰工程，成功合成了高 k 2D Sr1.8Bi0.2Nan-3NbnO3n+1（八面体单元，n = 3-5）纳米片，并在超薄薄膜（10 nm 以下）中实现了铁电特性。这种纳米片是通过基于溶液的阳离子交换工艺合成的，并采用 Langmuir-Blodgett (LB) 法沉积。随着 NbO6 八面体层的增加，纳米片的厚度也随之增加，带隙分别调谐到 3.80 eV（n = 3）、3.76 eV（n = 4）和 3.70 eV（n = 5）。此外，5 层堆叠纳米薄膜的介电常数分别增加到 26（n = 3）、33（n = 4）和 62（n = 5）。特别是，由于 A 位的 Sr/Bi/Na 离子尺寸不匹配，增加的包晶层表现出较大的畸变，并且由于奇数 n 数导致沿 c 轴的自发极化，从而促进了局部铁电不稳定性。我们通过极化-电场（P-E）滞后研究了 Pt/ 5 层 Sr1.8Bi0.2Na2Nb5O16 / Nb:STO 电容器的稳定铁电性；矫顽力电场（Ec）为 338 kV cm-1，残余极化（Pr）为 2.36 μC cm-2。超薄二维材料的铁电特性可推动下一代电子学的有趣创新。
{"title":"Layer control of Sr1.8Bi0.2Nan-3NbnO3n+1 (n = 3–5) perovskite nanosheets: dielectric to ferroelectric transition of film deposited by Langmuir Blodgett method","authors":"So-Yeon Yoo, Haena Yim, Ahrom Ryu, Chansoo Yoon, Bae Ho Park, Sahn Nahm, Ji-Won Choi","doi":"10.1038/s41699-023-00418-9","DOIUrl":"10.1038/s41699-023-00418-9","url":null,"abstract":"Solution-based processable high-k 2-dimensional (2D) ferroelectrics have attracted significant interest for use in next-generation nanoelectronics. Although few studies on potential 2D ferroelectric nanosheets in local areas have been conducted, reports on the thin-film characteristics applicable to the device are insufficient. In this study, we successfully synthesize high-k 2D Sr1.8Bi0.2Nan-3NbnO3n+1 (octahedral units, n = 3–5) nanosheets by the engineering of the n of NbO6 octahedral layers with A-site modification, and realized ferroelectric characteristics in ultrathin films (below 10 nm). The nanosheets are synthesized by a solution-based cation exchange process and deposited using the Langmuir-Blodgett (LB) method. As increasing the NbO6 octahedral layer, the thickness of the nanosheets increased and the band gaps are tuned to 3.80 eV (n = 3), 3.76 eV (n = 4), and 3.70 eV (n = 5). In addition, the dielectric permittivity of the 5-layer stacked nanofilm increase to 26 (n = 3), 33 (n = 4), and 62 (n = 5). In particular, the increased perovskite layer exhibits large distortions due to the size mismatch of Sr/Bi/Na ions at the A-site and promotes local ferroelectric instability due to its spontaneous polarization along the c-axis caused by an odd n number. We investigate the stable ferroelectricity in Pt/ 5-layer Sr1.8Bi0.2Na2Nb5O16 / Nb:STO capacitor by polarization-electric field (P-E) hysteresis; the coercive electric field (Ec) was 338 kV cm−1 and the remnant polarization (Pr) 2.36 μC cm−2. The ferroelectric properties of ultrathin 2D materials could drive interesting innovations in next-generation electronics.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-7"},"PeriodicalIF":9.7,"publicationDate":"2023-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00418-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45652312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-08-07DOI: 10.1038/s41699-023-00413-0
Danis I. Badrtdinov, Georgy V. Pushkarev, Mikhail I. Katsnelson, Alexander N. Rudenko
We study intrinsic charge-carrier scattering mechanisms and determine their contribution to the transport properties of the two-dimensional ferromagnet Fe3GeTe2. We use state-of-the-art first-principles calculations combined with the model approaches to elucidate the role of the electron-phonon and electron-magnon interactions in the electronic transport. Our findings show that the charge carrier scattering in Fe3GeTe2 is dominated by the electron-phonon interaction, while the role of magnetic excitations is marginal. At the same time, the magnetic ordering is shown to effect essentially on the electron-phonon coupling and its temperature dependence. This leads to a sublinear temperature dependence of the electrical resistivity near the Curie temperature, which is in line with experimental observations. The room temperature resistivity is estimated to be ~ 35 μΩ ⋅ cm which may be considered as a lower intrinsic limit for monolayer Fe3GeTe2.
{"title":"Electron transport and scattering mechanisms in ferromagnetic monolayer Fe3GeTe2","authors":"Danis I. Badrtdinov, Georgy V. Pushkarev, Mikhail I. Katsnelson, Alexander N. Rudenko","doi":"10.1038/s41699-023-00413-0","DOIUrl":"10.1038/s41699-023-00413-0","url":null,"abstract":"We study intrinsic charge-carrier scattering mechanisms and determine their contribution to the transport properties of the two-dimensional ferromagnet Fe3GeTe2. We use state-of-the-art first-principles calculations combined with the model approaches to elucidate the role of the electron-phonon and electron-magnon interactions in the electronic transport. Our findings show that the charge carrier scattering in Fe3GeTe2 is dominated by the electron-phonon interaction, while the role of magnetic excitations is marginal. At the same time, the magnetic ordering is shown to effect essentially on the electron-phonon coupling and its temperature dependence. This leads to a sublinear temperature dependence of the electrical resistivity near the Curie temperature, which is in line with experimental observations. The room temperature resistivity is estimated to be ~ 35 μΩ ⋅ cm which may be considered as a lower intrinsic limit for monolayer Fe3GeTe2.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-7"},"PeriodicalIF":9.7,"publicationDate":"2023-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00413-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41695444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a theoretical investigation of exciton-mediated Förster resonant energy transfers (FRET’s) from photoexcited quantum dots (QD’s) to transition-metal dichalcogenide monolayers (TMD-ML’s), implemented by the quantum theory of FRET on the base of first-principles-calculated exciton fine structures. With the enhanced electron-hole Coulomb interactions, atomically thin TMD-MLs are shown to serve as an exceptional platform for FRET that are mediated purely by excitons and take full advantage of the superior excitonic properties. Remarkably, the energy-transfer responses of atomically thin TMD-ML’s are shown to be dictated by the momentum-forbidden dark excitons rather than the commonly recognized bright ones. Specifically, the longitudinal dark exciton states following the exchange-driven light-like linear band dispersion play a key role in grading up the efficiency and robustness of FRET of TMD-ML against the inhomogeneity of QD-donor ensembles. With the essential involvement of dark excitons, the FRET responses of TMD-ML’s no longer follow the distance power law as classically predicted and, notably, cannot manifest the dimensionality of the donor-acceptor system.
{"title":"Essential role of momentum-forbidden dark excitons in the energy transfer responses of monolayer transition-metal dichalcogenides","authors":"Jhen-Dong Lin, Ping-Yuan Lo, Guan-Hao Peng, Wei-Hua Li, Shiang-Yu Huang, Guang-Yin Chen, Shun-Jen Cheng","doi":"10.1038/s41699-023-00414-z","DOIUrl":"10.1038/s41699-023-00414-z","url":null,"abstract":"We present a theoretical investigation of exciton-mediated Förster resonant energy transfers (FRET’s) from photoexcited quantum dots (QD’s) to transition-metal dichalcogenide monolayers (TMD-ML’s), implemented by the quantum theory of FRET on the base of first-principles-calculated exciton fine structures. With the enhanced electron-hole Coulomb interactions, atomically thin TMD-MLs are shown to serve as an exceptional platform for FRET that are mediated purely by excitons and take full advantage of the superior excitonic properties. Remarkably, the energy-transfer responses of atomically thin TMD-ML’s are shown to be dictated by the momentum-forbidden dark excitons rather than the commonly recognized bright ones. Specifically, the longitudinal dark exciton states following the exchange-driven light-like linear band dispersion play a key role in grading up the efficiency and robustness of FRET of TMD-ML against the inhomogeneity of QD-donor ensembles. With the essential involvement of dark excitons, the FRET responses of TMD-ML’s no longer follow the distance power law as classically predicted and, notably, cannot manifest the dimensionality of the donor-acceptor system.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-11"},"PeriodicalIF":9.7,"publicationDate":"2023-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00414-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47548456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-15DOI: 10.1038/s41699-023-00407-y
Justin Boddison-Chouinard, Alex Bogan, Pedro Barrios, Jean Lapointe, Kenji Watanabe, Takashi Taniguchi, Jarosław Pawłowski, Daniel Miravet, Maciej Bieniek, Pawel Hawrylak, Adina Luican-Mayer, Louis Gaudreau
Among quantum devices based on 2D materials, gate-defined quantum confined 1D channels are much less explored, especially in the high-mobility regime where many-body interactions play an important role. We present the results of measurements and theory of conductance quantization in a gate-defined one-dimensional channel in a single layer of transition metal dichalcogenide material WSe2. In the quasi-ballistic regime of our high-mobility sample, we report conductance quantization steps in units of e2/h for a wide range of carrier concentrations. Magnetic field measurements show that as the field is raised, higher conductance plateaus move to accurate quantized values and then shift to lower conductance values while the e2/h plateau remains locked. Based on microscopic atomistic tight-binding theory, we show that in this material, valley and spin degeneracies result in 2 e2/h conductance steps for noninteracting holes, suggesting that symmetry-breaking mechanisms such as valley polarization dominate the transport properties of such quantum structures.
{"title":"Anomalous conductance quantization of a one-dimensional channel in monolayer WSe2","authors":"Justin Boddison-Chouinard, Alex Bogan, Pedro Barrios, Jean Lapointe, Kenji Watanabe, Takashi Taniguchi, Jarosław Pawłowski, Daniel Miravet, Maciej Bieniek, Pawel Hawrylak, Adina Luican-Mayer, Louis Gaudreau","doi":"10.1038/s41699-023-00407-y","DOIUrl":"10.1038/s41699-023-00407-y","url":null,"abstract":"Among quantum devices based on 2D materials, gate-defined quantum confined 1D channels are much less explored, especially in the high-mobility regime where many-body interactions play an important role. We present the results of measurements and theory of conductance quantization in a gate-defined one-dimensional channel in a single layer of transition metal dichalcogenide material WSe2. In the quasi-ballistic regime of our high-mobility sample, we report conductance quantization steps in units of e2/h for a wide range of carrier concentrations. Magnetic field measurements show that as the field is raised, higher conductance plateaus move to accurate quantized values and then shift to lower conductance values while the e2/h plateau remains locked. Based on microscopic atomistic tight-binding theory, we show that in this material, valley and spin degeneracies result in 2 e2/h conductance steps for noninteracting holes, suggesting that symmetry-breaking mechanisms such as valley polarization dominate the transport properties of such quantum structures.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-7"},"PeriodicalIF":9.7,"publicationDate":"2023-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00407-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138506608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-07-10DOI: 10.1038/s41699-023-00403-2
Muhammad Sufyan Ramzan, Zachary A. H. Goodwin, Arash A. Mostofi, Agnieszka Kuc, Johannes Lischner
In graphene, charged defects break the electron-hole symmetry and can even give rise to exotic collapse states when the defect charge exceeds a critical value which is proportional to the Fermi velocity. In this work, we investigate the electronic properties of twisted bilayer graphene (tBLG) with charged defects using tight-binding calculations. Like monolayer graphene, tBLG exhibits linear bands near the Fermi level but with a dramatically reduced Fermi velocity near the magic angle (approximately 1.1°). This suggests that the critical value of the defect charge in magic-angle tBLG should also be very small. We find that charged defects give rise to significant changes in the low-energy electronic structure of tBLG. Depending on the defect position in the moiré unit cell, it is possible to open a band gap or to induce an additional flattening of the low-energy valence and conduction bands. Our calculations suggest that the collapse states of the two monolayers hybridize in the twisted bilayer. However, their in-plane localization remains largely unaffected by the presence of the additional twisted layer because of the different length scales of the moiré lattice and the monolayer collapse state wavefunctions. These predictions can be tested in scanning tunneling spectroscopy experiments.
{"title":"Effect of Coulomb impurities on the electronic structure of magic angle twisted bilayer graphene","authors":"Muhammad Sufyan Ramzan, Zachary A. H. Goodwin, Arash A. Mostofi, Agnieszka Kuc, Johannes Lischner","doi":"10.1038/s41699-023-00403-2","DOIUrl":"10.1038/s41699-023-00403-2","url":null,"abstract":"In graphene, charged defects break the electron-hole symmetry and can even give rise to exotic collapse states when the defect charge exceeds a critical value which is proportional to the Fermi velocity. In this work, we investigate the electronic properties of twisted bilayer graphene (tBLG) with charged defects using tight-binding calculations. Like monolayer graphene, tBLG exhibits linear bands near the Fermi level but with a dramatically reduced Fermi velocity near the magic angle (approximately 1.1°). This suggests that the critical value of the defect charge in magic-angle tBLG should also be very small. We find that charged defects give rise to significant changes in the low-energy electronic structure of tBLG. Depending on the defect position in the moiré unit cell, it is possible to open a band gap or to induce an additional flattening of the low-energy valence and conduction bands. Our calculations suggest that the collapse states of the two monolayers hybridize in the twisted bilayer. However, their in-plane localization remains largely unaffected by the presence of the additional twisted layer because of the different length scales of the moiré lattice and the monolayer collapse state wavefunctions. These predictions can be tested in scanning tunneling spectroscopy experiments.","PeriodicalId":19227,"journal":{"name":"npj 2D Materials and Applications","volume":" ","pages":"1-8"},"PeriodicalIF":9.7,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.nature.com/articles/s41699-023-00403-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47769892","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：