Pub Date : 2024-01-04DOI: 10.1088/2053-1583/ad1ae8
Jakub Jasinski, Joshua Thompson, Swaroop Palai, Maciej Smiertka, M. Dyksik, T. Taniguchi, Kenji Watanabe, Michał Baranowskki, Duncan K. Maude, A. Surrente, E. Malic, P. Płochocka
Intervalley scattering mechanisms strongly affect the dynamics of excitonic complexes in transition metal dichalcogenide monolayers. Here, we investigate the excitation energy dependence of the valley polarization of excitons in a WSe2 monolayer. We observe that the valley polarization drastically decreases when the excitation is resonant with the B1s resonance. This behaviour can be explained by a Dexter-like coupling in the momentum space between exciton states residing in opposite valleys but with the same spin configuration. This induces a net transfer of the exciton population from the optically driven valley towards the opposite, undriven valley. We observe the long-term fingerprints of this population transfer, as a vanishing valley polarization for the neutral exciton, and a negative valley polarization for biexcitonic complexes, in qualitative agreement with theoretical predictions based on a fully microscopic many-particle approach. This, together with a decrease of the PL energy when the excitation is resonant with the B1s state, points to the prominent role of the Dexter-like coupling in the exciton dynamics of atomically thin semiconductors.
{"title":"Control of the valley polarization of monolayer WSe2 by dexter-like coupling","authors":"Jakub Jasinski, Joshua Thompson, Swaroop Palai, Maciej Smiertka, M. Dyksik, T. Taniguchi, Kenji Watanabe, Michał Baranowskki, Duncan K. Maude, A. Surrente, E. Malic, P. Płochocka","doi":"10.1088/2053-1583/ad1ae8","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1ae8","url":null,"abstract":"\u0000 Intervalley scattering mechanisms strongly affect the dynamics of excitonic complexes in transition metal dichalcogenide monolayers. Here, we investigate the excitation energy dependence of the valley polarization of excitons in a WSe2 monolayer. We observe that the valley polarization drastically decreases when the excitation is resonant with the B1s resonance. This behaviour can be explained by a Dexter-like coupling in the momentum space between exciton states residing in opposite valleys but with the same spin configuration. This induces a net transfer of the exciton population from the optically driven valley towards the opposite, undriven valley. We observe the long-term fingerprints of this population transfer, as a vanishing valley polarization for the neutral exciton, and a negative valley polarization for biexcitonic complexes, in qualitative agreement with theoretical predictions based on a fully microscopic many-particle approach. This, together with a decrease of the PL energy when the excitation is resonant with the B1s state, points to the prominent role of the Dexter-like coupling in the exciton dynamics of atomically thin semiconductors.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"34 12","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139385408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-04DOI: 10.1088/2053-1583/ad10bc
E M Agapov, I A Kruglov, A A Katanin
Monolayer Fe2C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe2C within the DFT+DMFT approach. We establish the existence of local magnetic moments μloc=3.3μB in this compound, characterized by sufficiently long lifetime of τ∼350 fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. At low temperatures, we obtain the strongest exchange interaction 11 meV between next nearest neighboring Fe atoms, located above (or below) the carbon plane, and the subleading interaction 6 meV between the next to next nearest neighboring atoms, located across the carbon plane. The resulting dependence of the Berzinskii–Kosterlitz–Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained. The BKT temperature for the pristine Fe2C is TBKT≃300 K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.
{"title":"MXene Fe2C as a promising candidate for the 2D XY ferromagnet","authors":"E M Agapov, I A Kruglov, A A Katanin","doi":"10.1088/2053-1583/ad10bc","DOIUrl":"https://doi.org/10.1088/2053-1583/ad10bc","url":null,"abstract":"Monolayer Fe<sub>2</sub>C is expected to possess strong electronic correlations, which can significantly contribute to electronic and magnetic properties. In this study we consider electronic and magnetic properties of MXene Fe<sub>2</sub>C within the DFT+DMFT approach. We establish the existence of local magnetic moments <inline-formula>\u0000<tex-math><?CDATA $mu_{mathrm{loc}} = 3.3,mu_B$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msub><mml:mi>μ</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">l</mml:mi><mml:mi mathvariant=\"normal\">o</mml:mi><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo>=</mml:mo><mml:mn>3.3</mml:mn><mml:msub><mml:mi>μ</mml:mi><mml:mi>B</mml:mi></mml:msub></mml:math>\u0000<inline-graphic xlink:href=\"tdmad10bcieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> in this compound, characterized by sufficiently long lifetime of <inline-formula>\u0000<tex-math><?CDATA $tausim 350$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mi>τ</mml:mi><mml:mo>∼</mml:mo><mml:mn>350</mml:mn></mml:math>\u0000<inline-graphic xlink:href=\"tdmad10bcieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> fs. We also calculate exchange interaction parameters accounting for electronic correlations using the recently developed approach for paramagnetic phase. At low temperatures, we obtain the strongest exchange interaction 11 meV between next nearest neighboring Fe atoms, located above (or below) the carbon plane, and the subleading interaction 6 meV between the next to next nearest neighboring atoms, located across the carbon plane. The resulting dependence of the Berzinskii–Kosterlitz–Thouless (BKT) and Curie temperatures on magnetic anisotropy is obtained. The BKT temperature for the pristine Fe<sub>2</sub>C is <inline-formula>\u0000<tex-math><?CDATA $T_{mathrm{BKT}}simeq 300$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">B</mml:mi><mml:mi mathvariant=\"normal\">K</mml:mi><mml:mi mathvariant=\"normal\">T</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo>≃</mml:mo><mml:mn>300</mml:mn></mml:math>\u0000<inline-graphic xlink:href=\"tdmad10bcieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> K, which makes this compound a good candidate for the two-dimensional ferromagnet with XY anisotropy.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"29 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139094510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The hybrid-induced photogating effect is considered as an effective way for photoconductance modulating in low-dimensional photodetectors. Besides, through constructing the local photogate vertical heterostructures on 2D SnS2 surface can significantly increase its photoconductive gain. However, the potential of this photogain mechanism for SnS2 films has not yet been revealed in practical photodetection devices. To investigate its special advantages on promoting the optical-sensing activity, the high-quality SnS2 films with discrete, micro-area, and uniform rubrene-nanodots modification have been prepared. Benefit from the local interfacial photogating effect induced by hole trap states by rubrene-nanodots, the light-absorption and carrier-excitation efficiencies were significantly enhanced. Afterwards, the high-performance photodetector was designed based on the photogate vertical heterostructures of rubrene-nanodots/SnS2, which demonstrated an enhanced photoelectric response to 1064 nm light. Note that the maximum photocurrent density, photoresponsivity, and photodetectivity can reach up to 0.389 mA·cm-2, 388.71 mA·W-1, and 1.13×1010 Jones, respectively. Importantly, the optimal band-structure offsets accelerated the localized hole transfer from SnS2 film to rubrene-nanodots. The trapped holes in rubrene-nanodots induced an enhanced interface gating effect, which may help to modulate the number and lifetime of excess electrons under light illuminations. These superior features make the newly-developed photodetector be suitable for future multifunctional photodetection applications.
{"title":"Photogating Enhanced Photodetectors Dominated by Rubrene Nanodots Modified SnS2 Films","authors":"Guoxiang Si, Fangjun Liu, Lizhao Su, Zhaoxuan Wu, Qi Zhang, Shuoqi Sun, Hongbin Zhang","doi":"10.1088/2053-1583/ad1a6d","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6d","url":null,"abstract":"\u0000 The hybrid-induced photogating effect is considered as an effective way for photoconductance modulating in low-dimensional photodetectors. Besides, through constructing the local photogate vertical heterostructures on 2D SnS2 surface can significantly increase its photoconductive gain. However, the potential of this photogain mechanism for SnS2 films has not yet been revealed in practical photodetection devices. To investigate its special advantages on promoting the optical-sensing activity, the high-quality SnS2 films with discrete, micro-area, and uniform rubrene-nanodots modification have been prepared. Benefit from the local interfacial photogating effect induced by hole trap states by rubrene-nanodots, the light-absorption and carrier-excitation efficiencies were significantly enhanced. Afterwards, the high-performance photodetector was designed based on the photogate vertical heterostructures of rubrene-nanodots/SnS2, which demonstrated an enhanced photoelectric response to 1064 nm light. Note that the maximum photocurrent density, photoresponsivity, and photodetectivity can reach up to 0.389 mA·cm-2, 388.71 mA·W-1, and 1.13×1010 Jones, respectively. Importantly, the optimal band-structure offsets accelerated the localized hole transfer from SnS2 film to rubrene-nanodots. The trapped holes in rubrene-nanodots induced an enhanced interface gating effect, which may help to modulate the number and lifetime of excess electrons under light illuminations. These superior features make the newly-developed photodetector be suitable for future multifunctional photodetection applications.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"20 6","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139388930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a6b
M. Birch, L. Powalla, K. Litzius, V. Nehruji, Ondrej Hovorka, S. Wintz, F. Schulz, D. Mayoh, G. Balakrishnan, Markus Weigand, Marko Burghard, Gisela Schütz
Two-dimensional (2D) van der Waals (vdW) magnets have recently emerged as novel skyrmion hosts. This discovery has opened a new material platform for tuning the properties of topological spin textures, such as by exploiting proximity effects induced by stacking of 2D materials into heterostructures, or by directly manipulating the structural composition of the host material. Previous works have considered the effect of varied composition in the bulk crystals of the vdW magnet Fe3-xGeTe2, but so far the effects on the hosted spin textures have not been thoroughly investigated. In this work, real-space x-ray microscopy is utilized to image magnetic stripe domain, skyrmion and composite skyrmion states in exfoliated flakes of Fe3-xGeTe2 with varying Fe deficiency x. In combination with supporting mean-field and micromagnetic simulations, the significant alterations in the magnetic phase diagrams of the flakes, and thus the stability of the observed spin textures, are revealed. These arise as a result of the varying temperature dependence of the fundamental magnetic properties, which are greater than can be explained by the removal of spins, and are consistent with previously reported changes in the electronic band structure via the Fe deficiency.
二维（2D）范德华（vdW）磁体是最近出现的新型天空离子宿主。这一发现为调整拓扑自旋纹理的特性开辟了一个新的材料平台，例如利用二维材料堆叠成异质结构所引起的邻近效应，或直接操纵宿主材料的结构成分。之前的研究已经考虑了 vdW 磁体 Fe3-xGeTe2 块体晶体中不同成分的影响，但迄今为止尚未深入研究其对宿主自旋纹理的影响。在这项研究中，利用实空间 X 射线显微镜对不同缺铁量 x 的 Fe3-xGeTe2 剥离薄片中的磁条畴、天磁子和复合天磁子态进行了成像。这些变化是基本磁性随温度变化而变化的结果，超出了去除自旋所能解释的范围，并且与之前报道的电子能带结构因铁元素缺乏而发生的变化相一致。
{"title":"Control of stripe, skyrmion and skyrmionium formation in the 2D magnet Fe3−xGeTe2 by varying composition","authors":"M. Birch, L. Powalla, K. Litzius, V. Nehruji, Ondrej Hovorka, S. Wintz, F. Schulz, D. Mayoh, G. Balakrishnan, Markus Weigand, Marko Burghard, Gisela Schütz","doi":"10.1088/2053-1583/ad1a6b","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6b","url":null,"abstract":"\u0000 Two-dimensional (2D) van der Waals (vdW) magnets have recently emerged as novel skyrmion hosts. This discovery has opened a new material platform for tuning the properties of topological spin textures, such as by exploiting proximity effects induced by stacking of 2D materials into heterostructures, or by directly manipulating the structural composition of the host material. Previous works have considered the effect of varied composition in the bulk crystals of the vdW magnet Fe3-xGeTe2, but so far the effects on the hosted spin textures have not been thoroughly investigated. In this work, real-space x-ray microscopy is utilized to image magnetic stripe domain, skyrmion and composite skyrmion states in exfoliated flakes of Fe3-xGeTe2 with varying Fe deficiency x. In combination with supporting mean-field and micromagnetic simulations, the significant alterations in the magnetic phase diagrams of the flakes, and thus the stability of the observed spin textures, are revealed. These arise as a result of the varying temperature dependence of the fundamental magnetic properties, which are greater than can be explained by the removal of spins, and are consistent with previously reported changes in the electronic band structure via the Fe deficiency.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"4 2","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a6f
Siwon Oh, Han-gyu Kim, Jungcheol Kim, Huiseok Jeong, H. Choi, Hyeonsik Cheong
The low-frequency interlayer vibration modes in bilayer-MoS2/monolayer-WSe2 heterostructures were investigated to study the modification of interlayer interactions due to the moiré periodicity. The interplay of the interlayer interaction within bilayer MoS2 and the interfacial interaction between the two materials results in rich features in the phonon spectra. Several shear and breathing modes are observed for samples with small twist angles (<10°), whereas only one shear and two breathing modes are observed for larger twist angles. For larger twist angles, the interfacial interaction between the two materials amounts to ∼75% of the intrinsic interlayer interaction between the MoS2 layers. The phonon spectrum evolves non-monotonically as the twist angle increases, which is explained with the help of atomistic calculations.
{"title":"Modification of interlayer interaction in bilayer MoS2 due to monolayer WSe2 in heterostructures","authors":"Siwon Oh, Han-gyu Kim, Jungcheol Kim, Huiseok Jeong, H. Choi, Hyeonsik Cheong","doi":"10.1088/2053-1583/ad1a6f","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6f","url":null,"abstract":"The low-frequency interlayer vibration modes in bilayer-MoS2/monolayer-WSe2 heterostructures were investigated to study the modification of interlayer interactions due to the moiré periodicity. The interplay of the interlayer interaction within bilayer MoS2 and the interfacial interaction between the two materials results in rich features in the phonon spectra. Several shear and breathing modes are observed for samples with small twist angles (<10°), whereas only one shear and two breathing modes are observed for larger twist angles. For larger twist angles, the interfacial interaction between the two materials amounts to ∼75% of the intrinsic interlayer interaction between the MoS2 layers. The phonon spectrum evolves non-monotonically as the twist angle increases, which is explained with the help of atomistic calculations.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"53 19","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a6a
A. Cadore, B. L. T. Rosa, I. Paradisanos, S. Mignuzzi, D. De Fazio, Eugene Alexeev, A. Dagkli, J. Muench, Georgios Kakavelakis, Sachin M. Schinde, D. Yoon, S. Tongay, Kenji Watanabe, T. Taniguchi, E. Lidorikis, I. Goykhman, G. Soavi, A. C. Ferrari
Layered material heterostructures (LMHs) can be used to fabricate electroluminescent devices operating in the visible spectral region. A major advantage of LMH-light emitting diodes (LEDs) is that electroluminescence (EL) emission can be tuned across that of different exciton complexes (e.g. biexcitons, trions, quintons) by controlling the charge density. However, these devices have an EL quantum efficiency as low as~10−4%. Here, we show that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of monolayer WS2-LEDs boosts EL quantum efficiency by over one order of magnitude at room temperature. Non-treated devices emit light mainly from negatively charged excitons, while the emission in treated ones predominantly involves radiative recombination of neutral excitons. This paves the way to tunable and efficient LMH-LEDs.
层状材料异质结构（LMH）可用于制造在可见光谱区工作的电致发光器件。层状材料异质结构发光二极管（LED）的一个主要优点是可以通过控制电荷密度来调节不同激子复合物（如双激子、三激子、五激子）的电致发光（EL）发射。然而，这些器件的电致发光量子效率低至~10-4%。在这里，我们展示了对单层 WS2-LED 进行超酸性双（三氟甲烷）磺酰亚胺（TFSI）处理后，在室温下可将 EL 量子效率提高一个数量级以上。未经处理的器件主要通过带负电荷的激子发光，而经过处理的器件则主要通过中性激子的辐射重组发光。这为实现可调且高效的 LMH-LED 铺平了道路。
{"title":"Monolayer WS2 electro- and photo-luminescence enhancement by TFSI treatment","authors":"A. Cadore, B. L. T. Rosa, I. Paradisanos, S. Mignuzzi, D. De Fazio, Eugene Alexeev, A. Dagkli, J. Muench, Georgios Kakavelakis, Sachin M. Schinde, D. Yoon, S. Tongay, Kenji Watanabe, T. Taniguchi, E. Lidorikis, I. Goykhman, G. Soavi, A. C. Ferrari","doi":"10.1088/2053-1583/ad1a6a","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6a","url":null,"abstract":"\u0000 Layered material heterostructures (LMHs) can be used to fabricate electroluminescent devices operating in the visible spectral region. A major advantage of LMH-light emitting diodes (LEDs) is that electroluminescence (EL) emission can be tuned across that of different exciton complexes (e.g. biexcitons, trions, quintons) by controlling the charge density. However, these devices have an EL quantum efficiency as low as~10−4%. Here, we show that the superacid bis-(triuoromethane)sulfonimide (TFSI) treatment of monolayer WS2-LEDs boosts EL quantum efficiency by over one order of magnitude at room temperature. Non-treated devices emit light mainly from negatively charged excitons, while the emission in treated ones predominantly involves radiative recombination of neutral excitons. This paves the way to tunable and efficient LMH-LEDs.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"55 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139450854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a71
Junwei Huang, Caorong Zhang, K. Zhai, Feng Qin, Lingyi Ao, Zeya Li, Ling Zhou, Ming Tang, Xueting Dai, Caiyu Qiu, Yi Zhang, F. Wen, Zhongyuan Liu, Hongtao Yuan
The discovery of superconductivity and its modulation are long-standing cutting-edge research topics in condensed matter physics. As a powerful tool, the high-pressure technique can be used to achieve novel superconductors and tune their physical properties. One typical example is binary germanium phosphides with different stoichiometries, which exhibit abundant physical properties with layered lattice structures similar to blue phosphorus. The detailed phase diagrams of the Ge–P systems are important for understanding the influence of stoichiometry on pressure-driven superconductivity, but it remains unexplored. Here, we measured and compared the detailed superconducting phase diagrams of the Ge–P systems of layered isostructural germanium phosphides GeP3 and GeP5 under pressure. Even though these two binary phosphides exhibit obviously different atomic occupations in the crystal structure due to their distinct stoichiometric ratios, the onset superconducting transition temperatures Tc of GeP3 and GeP5 both show dramatic enhancements from ∼2.5 K at 12.0 GPa to the maximum values of ∼9.0 K at 28.0 GPa, which are higher than those of other binary metal phosphides. Such pressure-enhanced superconductivity therein is accompanied by significant pressure-induced phonon mode softening, which is confirmed via in situ high-pressure Raman measurements. Our observations deepen the physical understanding of pressure-driven superconductivity in phosphorous-rich layered compounds and pave the way for potential applications in microsuperconducting devices.
{"title":"Pressure-driven superconductivity in layered isostructural germanium phosphides","authors":"Junwei Huang, Caorong Zhang, K. Zhai, Feng Qin, Lingyi Ao, Zeya Li, Ling Zhou, Ming Tang, Xueting Dai, Caiyu Qiu, Yi Zhang, F. Wen, Zhongyuan Liu, Hongtao Yuan","doi":"10.1088/2053-1583/ad1a71","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a71","url":null,"abstract":"The discovery of superconductivity and its modulation are long-standing cutting-edge research topics in condensed matter physics. As a powerful tool, the high-pressure technique can be used to achieve novel superconductors and tune their physical properties. One typical example is binary germanium phosphides with different stoichiometries, which exhibit abundant physical properties with layered lattice structures similar to blue phosphorus. The detailed phase diagrams of the Ge–P systems are important for understanding the influence of stoichiometry on pressure-driven superconductivity, but it remains unexplored. Here, we measured and compared the detailed superconducting phase diagrams of the Ge–P systems of layered isostructural germanium phosphides GeP3 and GeP5 under pressure. Even though these two binary phosphides exhibit obviously different atomic occupations in the crystal structure due to their distinct stoichiometric ratios, the onset superconducting transition temperatures Tc of GeP3 and GeP5 both show dramatic enhancements from ∼2.5 K at 12.0 GPa to the maximum values of ∼9.0 K at 28.0 GPa, which are higher than those of other binary metal phosphides. Such pressure-enhanced superconductivity therein is accompanied by significant pressure-induced phonon mode softening, which is confirmed via in situ high-pressure Raman measurements. Our observations deepen the physical understanding of pressure-driven superconductivity in phosphorous-rich layered compounds and pave the way for potential applications in microsuperconducting devices.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"38 1","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a6c
Valeria Maslova, Nina Voronova
Interlayer excitons in transition-metal dichalcogenide (TMD) bilayers, alongside their interplay with direct excitonic species, are supposed to offer a pathway towards robust nonlinearity, enabling the exploration of many-body quantum effects. We present a theoretical investigation of interaction among various exciton species within these structures where Coulomb attraction and repulsion are subject to reduced screening. For a homobilayer MoS2, we examine both direct, spatially-indirect, and hybridised excitons, considering the effects of direct and exchange interaction of electrons and holes distributed across one or different layers. Similar physics arises in perfectly aligned twisted TMD heterobilayers which support the direct-to-indirect exciton hybridisation. Deriving the exciton-exciton interaction matrix elements, we unveil a distinct non-monotonic dependence of the interaction on transferred momentum, changing sign from repulsive to attractive even for ground-state excitons, and compare our results with existing calculations for monolayers. Our findings demonstrate that for large momenta involved in high-density effects (strongly correlated phases), the interaction is chiefly governed by the prevailing attractive exchange component. At the same time, at small momenta that are more relevant for rarefied systems, we find that the enhancement of the interaction constant for dipolar species compared to intralayer non-dipolar excitons may be hindered by the surrounding medium. We draw comparisons with existing experiments and discuss the implications of our findings on the collective effects in TMD-based systems of excitons and exciton-polaritons.
{"title":"Spatially-indirect and hybrid exciton-exciton interaction in MoS2 homobilayers","authors":"Valeria Maslova, Nina Voronova","doi":"10.1088/2053-1583/ad1a6c","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6c","url":null,"abstract":"\u0000 Interlayer excitons in transition-metal dichalcogenide (TMD) bilayers, alongside their interplay with direct excitonic species, are supposed to offer a pathway towards robust nonlinearity, enabling the exploration of many-body quantum effects. We present a theoretical investigation of interaction among various exciton species within these structures where Coulomb attraction and repulsion are subject to reduced screening. For a homobilayer MoS2, we examine both direct, spatially-indirect, and hybridised excitons, considering the effects of direct and exchange interaction of electrons and holes distributed across one or different layers. Similar physics arises in perfectly aligned twisted TMD heterobilayers which support the direct-to-indirect exciton hybridisation. Deriving the exciton-exciton interaction matrix elements, we unveil a distinct non-monotonic dependence of the interaction on transferred momentum, changing sign from repulsive to attractive even for ground-state excitons, and compare our results with existing calculations for monolayers. Our findings demonstrate that for large momenta involved in high-density effects (strongly correlated phases), the interaction is chiefly governed by the prevailing attractive exchange component. At the same time, at small momenta that are more relevant for rarefied systems, we find that the enhancement of the interaction constant for dipolar species compared to intralayer non-dipolar excitons may be hindered by the surrounding medium. We draw comparisons with existing experiments and discuss the implications of our findings on the collective effects in TMD-based systems of excitons and exciton-polaritons.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"112 4","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a6e
Jaekwang Song, Jong-Hwan Lee, Seoungwoong Park, Yunseok Lee, Chan-Jin Kim, Minchul Ahn, Byung Hee Hong
Area-selection reactions have been extensively investigated to control or change physicochemical properties of substances with micro- or nanoscale precision. Several polymeric materials called photoresists have been used to mask and pattern the specific region, which can block chemical reactions or deposition. However, they are not suitable for certain chemical reaction since they are vulnerable to high temperature. Here, we report the graphene mask to achieve area-selective chalcogenization, which is performed at high temperature by chemical vapor deposition method. Due to its physicochemical properties, graphene does not allow chalcogen precursor gases to penetrate into metal films. Several characterizations are performed to prove the successful sulfurization and selenization of molybdenum and tungsten films. As an application, WS2 field-effect transistors with graphene mask are fabricated, and they show the typical characteristics of transistors successfully. Therefore, we expect that graphene-assisted area-selective reaction can be utilized for various fields such as semiconductors, sensors, and etc.
{"title":"Area-selective chalcogenization of transition metals through graphene mask","authors":"Jaekwang Song, Jong-Hwan Lee, Seoungwoong Park, Yunseok Lee, Chan-Jin Kim, Minchul Ahn, Byung Hee Hong","doi":"10.1088/2053-1583/ad1a6e","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a6e","url":null,"abstract":"Area-selection reactions have been extensively investigated to control or change physicochemical properties of substances with micro- or nanoscale precision. Several polymeric materials called photoresists have been used to mask and pattern the specific region, which can block chemical reactions or deposition. However, they are not suitable for certain chemical reaction since they are vulnerable to high temperature. Here, we report the graphene mask to achieve area-selective chalcogenization, which is performed at high temperature by chemical vapor deposition method. Due to its physicochemical properties, graphene does not allow chalcogen precursor gases to penetrate into metal films. Several characterizations are performed to prove the successful sulfurization and selenization of molybdenum and tungsten films. As an application, WS2 field-effect transistors with graphene mask are fabricated, and they show the typical characteristics of transistors successfully. Therefore, we expect that graphene-assisted area-selective reaction can be utilized for various fields such as semiconductors, sensors, and etc.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"53 15","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451826","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-01-03DOI: 10.1088/2053-1583/ad1a70
Zamin Mamiyev, C. Tegenkamp
Graphene plasmons, including those in intercalated graphene, are an important research focus, with the promise of enabling light manipulation and providing a unique platform for gaining fundamental insights into many-body electronic interactions. In the present work, we discuss the results of low-energy plasmonic excitations in epitaxial quasi-free monolayer graphene formed by intercalation of Sn beneath the buffer layer on 4H-SiC(0001). The quantitative analysis of the sheet plasmon dispersion revealed that the Sn-induced ($1times1$) interface is metallic and results in formation of charge-neutral graphene. A redshift of the 2D plasmon was found, but only after doping with potassium. The Sn-diluted interface, revealing a ($sqrt{3}timessqrt{3}$) reconstruction and resulting in intrinsically n-type doped graphene, behaves comparably to the buffer layer for epitaxial monolayer graphene. Furthermore, it seems that a dipolar coupling of the longitudinal charge density fluctuations in graphene to the interface layer triggers the formation and the loss energy of a plasmonic multipole component, which therefore makes it suitable for studying proximity effects of excitations in electronically weakly coupled 2D heterosystems.
石墨烯等离子体，包括插层石墨烯中的等离子体，是一个重要的研究焦点，有望实现光操纵，并为从根本上了解多体电子相互作用提供了一个独特的平台。在本研究中，我们讨论了在 4H-SiC(0001) 缓冲层下插层锡形成的外延准无单层石墨烯中的低能质子激发结果。对片状等离子体色散的定量分析显示，锡诱导的（1times1$）界面是金属性的，并导致形成电荷中性的石墨烯。发现了二维等离子体的红移，但只有在掺入钾之后才会出现。锡稀释界面显示了（$sqrt{3}timessqrt{3}$）重构，并导致了本质上的 n 型掺杂石墨烯，其表现与外延单层石墨烯的缓冲层类似。此外，石墨烯中纵向电荷密度波动与界面层的双极耦合似乎引发了质子多极分量的形成和损耗能量，因此它适合研究电子弱耦合二维异质系统中激发的邻近效应。
{"title":"Exploring graphene-substrate interactions: Plasmonic excitation in Sn-intercalated epitaxial graphene","authors":"Zamin Mamiyev, C. Tegenkamp","doi":"10.1088/2053-1583/ad1a70","DOIUrl":"https://doi.org/10.1088/2053-1583/ad1a70","url":null,"abstract":"\u0000 Graphene plasmons, including those in intercalated graphene, are an important research focus, with the promise of enabling light manipulation and providing a unique platform for gaining fundamental insights into many-body electronic interactions. In the present work, we discuss the results of low-energy plasmonic excitations in epitaxial quasi-free monolayer graphene formed by intercalation of Sn beneath the buffer layer on 4H-SiC(0001). The quantitative analysis of the sheet plasmon dispersion revealed that the Sn-induced ($1times1$) interface is metallic and results in formation of charge-neutral graphene. A redshift of the 2D plasmon was found, but only after doping with potassium. The Sn-diluted interface, revealing a ($sqrt{3}timessqrt{3}$) reconstruction and resulting in intrinsically n-type doped graphene, behaves comparably to the buffer layer for epitaxial monolayer graphene. Furthermore, it seems that a dipolar coupling of the longitudinal charge density fluctuations in graphene to the interface layer triggers the formation and the loss energy of a plasmonic multipole component, which therefore makes it suitable for studying proximity effects of excitations in electronically weakly coupled 2D heterosystems.","PeriodicalId":6812,"journal":{"name":"2D Materials","volume":"4 8","pages":""},"PeriodicalIF":5.5,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139450931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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