The Experts below are selected from a list of 17868 Experts worldwide ranked by ideXlab platform
A Castro H Neto - One of the best experts on this subject based on the ideXlab platform.
-
photocarrier relaxation pathway in two dimensional semiconducting transition Metal Dichalcogenides
Nature Communications, 2014Co-Authors: Daichi Kozawa, Rajeev Kumar, A Carvalho, Kiran Kumar Amara, Weijie Zhao, Shunfeng Wang, Minglin Toh, R M Ribeiro, A Castro H NetoAbstract:Two-dimensional semiconducting transition Metal Dichalcogenides strongly absorb visible light. Kozawa et al. study the photocarrier relaxation in mono- and bilayer MX2 samples and find that loss of photocarriers by direct recombination becomes a second-order process when excitation is in resonance with band nesting.
-
band nesting and the optical response of two dimensional semiconducting transition Metal Dichalcogenides
Physical Review B, 2013Co-Authors: A Carvalho, R M Ribeiro, A Castro H NetoAbstract:We have studied the optical conductivity of two-dimensional (2D) semiconducting transition Metal Dichalcogenides using ab initio density functional theory. We find that this class of materials presents large optical response due to the phenomenon of band nesting. The tendency towards band nesting is enhanced by the presence of van Hove singularities in the band structure of these materials. Given that 2D crystals are atomically thin and naturally transparent, our results show that it is possible to have strong photon-electron interactions even in 2D.
-
charge density wave superconductivity and anomalous Metallic behavior in 2d transition Metal Dichalcogenides
Physical Review Letters, 2001Co-Authors: A Castro H NetoAbstract:We propose a theory for quasi-two-dimensional transition Metal Dichalcogenides that provides a unified microscopic picture of the charge density wave (CDW) and superconducting phases. We show, based on the electron-phonon coupling and Fermi surface topology, that a CDW order parameter with sixfold symmetry and nodes ( f-wave) gives a consistent description of the available experimental data. The elementary excitations in the CDW phase are Dirac electrons. The superconducting state has its origin on the attractive interaction mediated by phonons. The theory predicts strong deviations from Fermi liquid theory in the CDW phase.
Tony F Heinz - One of the best experts on this subject based on the ideXlab platform.
-
colloquium excitons in atomically thin transition Metal Dichalcogenides
Reviews of Modern Physics, 2018Co-Authors: Gang Wang, Tony F Heinz, Alexey Chernikov, Mikhail Glazov, Thierry Amand, X Marie, Bernhard UrbaszekAbstract:© 2018 American Physical Society. Atomically thin materials such as graphene and monolayer transition Metal Dichalcogenides (TMDs) exhibit remarkable physical properties resulting from their reduced dimensionality and crystal symmetry. The family of semiconducting transition Metal Dichalcogenides is an especially promising platform for fundamental studies of two-dimensional (2D) systems, with potential applications in optoelectronics and valleytronics due to their direct band gap in the monolayer limit and highly efficient light-matter coupling. A crystal lattice with broken inversion symmetry combined with strong spin-orbit interactions leads to a unique combination of the spin and valley degrees of freedom. In addition, the 2D character of the monolayers and weak dielectric screening from the environment yield a significant enhancement of the Coulomb interaction. The resulting formation of bound electron-hole pairs, or excitons, dominates the optical and spin properties of the material. Here recent progress in understanding of the excitonic properties in monolayer TMDs is reviewed and future challenges are laid out. Discussed are the consequences of the strong direct and exchange Coulomb interaction, exciton light-matter coupling, and influence of finite carrier and electron-hole pair densities on the exciton properties in TMDs. Finally, the impact on valley polarization is described and the tuning of the energies and polarization observed in applied electric and magnetic fields is summarized.
-
colloquium excitons in atomically thin transition Metal Dichalcogenides
Reviews of Modern Physics, 2018Co-Authors: Gang Wang, Tony F Heinz, Alexey Chernikov, Mikhail Glazov, Thierry Amand, X Marie, Bernhard UrbaszekAbstract:Atomically thin materials such as graphene and monolayer transition Metal Dichalcogenides (TMDs) exhibit remarkable physical properties resulting from their reduced dimensionality and crystal symmetry. The family of semiconducting transition Metal Dichalcogenides is an especially promising platform for fundamental studies of two-dimensional (2D) systems, with potential applications in optoelectronics and valleytronics due to their direct band gap in the monolayer limit and highly efficient light-matter coupling. A crystal lattice with broken inversion symmetry combined with strong spin-orbit interactions leads to a unique combination of the spin and valley degrees of freedom. In addition, the 2D character of the monolayers and weak dielectric screening from the environment yield a significant enhancement of the Coulomb interaction. The resulting formation of bound electron-hole pairs, or excitons, dominates the optical and spin properties of the material. Here recent progress in understanding of the excitonic properties in monolayer TMDs is reviewed and future challenges are laid out. Discussed are the consequences of the strong direct and exchange Coulomb interaction, exciton light-matter coupling, and influence of finite carrier and electron-hole pair densities on the exciton properties in TMDs. Finally, the impact on valley polarization is described and the tuning of the energies and polarization observed in applied electric and magnetic fields is summarized.
-
excitonic linewidth and coherence lifetime in monolayer transition Metal Dichalcogenides
Proceedings of SPIE, 2017Co-Authors: Malte Selig, Gunnar Berghäuser, Tony F Heinz, Alexey Chernikov, Ermin Malic, Archana Raja, Philipp Nagler, Christian Schuller, Tobias Korn, Andreas KnorrAbstract:Monolayers of transition Metal Dichalcogenides are direct gap semiconductors, which have attracted much attention in the recent past. Due to a strong Coulomb interaction, they possess strongly bound electron-hole pairs, with binding energies of hundreds of meV which is an order of magnitude larger than in conventional materials. Here, we investigate the microscopic origin of the homogeneous linewidth and coherence lifetime of excitonic resonances in monolayer molybdenum disulfide, taking exciton phonon scattering and radiative recombination into account. We find a superlinear increasing homogeneous linewidth from 2 meV at 5K to 14 meV at room temperature corresponding to a coherence lifetime of 160 fs and 25 fs.
-
spin and pseudospins in layered transition Metal Dichalcogenides
Nature Physics, 2014Co-Authors: Wang Yao, Di Xiao, Tony F HeinzAbstract:Understanding the physics of two-dimensional materials beyond graphene is of both fundamental and practical interest. Recent theoretical and experimental advances uncover the interplay between real spin and pseudospins in layered transition Metal Dichalcogenides.
-
spin and pseudospins in layered transition Metal Dichalcogenides
Nature Physics, 2014Co-Authors: Wang Yao, Di Xiao, Tony F HeinzAbstract:The recent emergence of two-dimensional layered materials — in particular the transition Metal Dichalcogenides — provides a new laboratory for exploring the internal quantum degrees of freedom of electrons and their potential for new electronics. These degrees of freedom are the real electron spin, the layer pseudospin, and the valley pseudospin. New methods for the quantum control of the spin and these pseudospins arise from the existence of Berry phase-related physical properties and strong spin–orbit coupling. The former leads to the versatile control of the valley pseudospin, whereas the latter gives rise to an interplay between the spin and the pseudospins. Here, we provide a brief review of both theoretical and experimental advances in this field. Understanding the physics of two-dimensional materials beyond graphene is of both fundamental and practical interest. Recent theoretical and experimental advances uncover the interplay between real spin and pseudospins in layered transition Metal Dichalcogenides.
Bernhard Urbaszek - One of the best experts on this subject based on the ideXlab platform.
-
colloquium excitons in atomically thin transition Metal Dichalcogenides
Reviews of Modern Physics, 2018Co-Authors: Gang Wang, Tony F Heinz, Alexey Chernikov, Mikhail Glazov, Thierry Amand, X Marie, Bernhard UrbaszekAbstract:© 2018 American Physical Society. Atomically thin materials such as graphene and monolayer transition Metal Dichalcogenides (TMDs) exhibit remarkable physical properties resulting from their reduced dimensionality and crystal symmetry. The family of semiconducting transition Metal Dichalcogenides is an especially promising platform for fundamental studies of two-dimensional (2D) systems, with potential applications in optoelectronics and valleytronics due to their direct band gap in the monolayer limit and highly efficient light-matter coupling. A crystal lattice with broken inversion symmetry combined with strong spin-orbit interactions leads to a unique combination of the spin and valley degrees of freedom. In addition, the 2D character of the monolayers and weak dielectric screening from the environment yield a significant enhancement of the Coulomb interaction. The resulting formation of bound electron-hole pairs, or excitons, dominates the optical and spin properties of the material. Here recent progress in understanding of the excitonic properties in monolayer TMDs is reviewed and future challenges are laid out. Discussed are the consequences of the strong direct and exchange Coulomb interaction, exciton light-matter coupling, and influence of finite carrier and electron-hole pair densities on the exciton properties in TMDs. Finally, the impact on valley polarization is described and the tuning of the energies and polarization observed in applied electric and magnetic fields is summarized.
-
colloquium excitons in atomically thin transition Metal Dichalcogenides
Reviews of Modern Physics, 2018Co-Authors: Gang Wang, Tony F Heinz, Alexey Chernikov, Mikhail Glazov, Thierry Amand, X Marie, Bernhard UrbaszekAbstract:Atomically thin materials such as graphene and monolayer transition Metal Dichalcogenides (TMDs) exhibit remarkable physical properties resulting from their reduced dimensionality and crystal symmetry. The family of semiconducting transition Metal Dichalcogenides is an especially promising platform for fundamental studies of two-dimensional (2D) systems, with potential applications in optoelectronics and valleytronics due to their direct band gap in the monolayer limit and highly efficient light-matter coupling. A crystal lattice with broken inversion symmetry combined with strong spin-orbit interactions leads to a unique combination of the spin and valley degrees of freedom. In addition, the 2D character of the monolayers and weak dielectric screening from the environment yield a significant enhancement of the Coulomb interaction. The resulting formation of bound electron-hole pairs, or excitons, dominates the optical and spin properties of the material. Here recent progress in understanding of the excitonic properties in monolayer TMDs is reviewed and future challenges are laid out. Discussed are the consequences of the strong direct and exchange Coulomb interaction, exciton light-matter coupling, and influence of finite carrier and electron-hole pair densities on the exciton properties in TMDs. Finally, the impact on valley polarization is described and the tuning of the energies and polarization observed in applied electric and magnetic fields is summarized.
-
exciton fine structure and spin decoherence in monolayers of transition Metal Dichalcogenides
Physical Review B, 2014Co-Authors: Mikhail Glazov, Thierry Amand, X Marie, D Lagarde, L Bouet, Bernhard UrbaszekAbstract:We study the neutral exciton energy spectrum fine structure and its spin dephasing in transition Metal Dichalcogenides such as ${\mathrm{MoS}}_{2}$. The interaction of the mechanical exciton with its macroscopic longitudinal electric field is taken into account. The splitting between the longitudinal and transverse excitons is calculated by means of the both electrodynamical approach and $\mathbit{k}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbit{p}$ perturbation theory. This long-range exciton exchange interaction can induce valley polarization decay. The estimated exciton spin dephasing time is in the picosecond range, in agreement with available experimental data.
E Bucher - One of the best experts on this subject based on the ideXlab platform.
-
high mobility field effect transistors based on transition Metal Dichalcogenides
Applied Physics Letters, 2004Co-Authors: Vitaly Podzorov, M E Gershenson, Ch Kloc, Roswitha Zeis, E BucherAbstract:We report on fabrication of field-effect transistors (FETs) based on transition Metal Dichalcogenides. The unique structure of single crystals of these layered inorganic semiconductors enables fabrication of FETs with intrinsically low field-effect threshold and high charge carrier mobility, comparable to that in the best single-crystal Si FETs (up to 500 cm2/V s for the p-type conductivity in the WSe2-based FETs at room temperature). These FETs demonstrate ambipolar operation. Owing to mechanical flexibility, they hold potential for applications in “flexible” electronics.
-
novel high mobility field effect transistors based on transition Metal Dichalcogenides
arXiv: Materials Science, 2004Co-Authors: Vitaly Podzorov, M E Gershenson, Ch Kloc, Roswitha Zeis, E BucherAbstract:We report on fabrication of novel field-effect transistors (FETs) based on transition Metal Dichalcogenides. The unique structure of single crystals of these layered inorganic semiconductors enables fabrication of FETs with intrinsically low field-effect threshold and high charge carrier mobility, comparable to that in the best single-crystal Si FETs (up to 500 cm2/Vs for the p-type conductivity in the WSe2-based FETs at room temperature). These novel FETs demonstrate ambipolar operation. Owing to mechanical flexibility, they hold potential for applications in "flexible" electronics.
R M Ribeiro - One of the best experts on this subject based on the ideXlab platform.
-
photocarrier relaxation pathway in two dimensional semiconducting transition Metal Dichalcogenides
Nature Communications, 2014Co-Authors: Daichi Kozawa, Rajeev Kumar, A Carvalho, Kiran Kumar Amara, Weijie Zhao, Shunfeng Wang, Minglin Toh, R M Ribeiro, A Castro H NetoAbstract:Two-dimensional semiconducting transition Metal Dichalcogenides strongly absorb visible light. Kozawa et al. study the photocarrier relaxation in mono- and bilayer MX2 samples and find that loss of photocarriers by direct recombination becomes a second-order process when excitation is in resonance with band nesting.
-
band nesting and the optical response of two dimensional semiconducting transition Metal Dichalcogenides
Physical Review B, 2013Co-Authors: A Carvalho, R M Ribeiro, A Castro H NetoAbstract:We have studied the optical conductivity of two-dimensional (2D) semiconducting transition Metal Dichalcogenides using ab initio density functional theory. We find that this class of materials presents large optical response due to the phenomenon of band nesting. The tendency towards band nesting is enhanced by the presence of van Hove singularities in the band structure of these materials. Given that 2D crystals are atomically thin and naturally transparent, our results show that it is possible to have strong photon-electron interactions even in 2D.