The Editorial Board invites you to submit your letters to EPL EPL is a leading international jour... more The Editorial Board invites you to submit your letters to EPL EPL is a leading international journal publishing original, innovative Letters in all areas of physics, ranging from condensed matter topics and interdisciplinary research to astrophysics, geophysics, plasma and fusion sciences, including those with application potential. The high profile of the journal combined with the excellent scientific quality of the articles ensures that EPL is an essential resource for its worldwide audience. EPL offers authors global visibility and a great opportunity to share their work with others across the whole of the physics community.
The transport properties of MAPbI3 are analyzed within a tight-binding model. We find a strong Fr... more The transport properties of MAPbI3 are analyzed within a tight-binding model. We find a strong Fröhlich interaction of electron and holes with the electrostatic potential induced by the longitudinal optical phonon modes. This potential induces a strong scattering and limits the electronic mobilities at room temperature to about 200 cm 2 =V s. With additional extrinsic disorder, a large fraction of the electrons and holes are localized, but they can diffuse by following nearly adiabatically the evolution of the electrostatic potential. This process of diffusion, at a rate which is given by the lattice dynamics, contributes to the unique electronic properties of this material.
Stacking layered materials revealed to be a very powerful method to tailor their electronic prope... more Stacking layered materials revealed to be a very powerful method to tailor their electronic properties. It has indeed been theoretically and experimentally shown that twisted bilayers of graphene (tBLG) with a rotation angle θ, forming a Moiré pattern, confine electrons in a tunable way as a function of θ. Here, we study electronic structure and transport in tBLG using tight-binding numerical calculations in commensurate twisted bilayer structures and a pertubative continuous theory, which is valid for not-too-small angles (θ >∼ 2 •). These two approaches allow us to understand the effect of θ on the local density of states, the electron lifetime due to disorder, the DC conductivity, and the conductivity quantum correction due to multiple scattering effects. We distinguish the cases where disorder is equally distributed over two layers or only one layer. When only one layer is disordered, diffusion properties depend strongly on θ, thus showing the effect of Moiré electronic localization at intermediate angles θ , ∼2 • < θ <∼ 20 • .
Organic semi-conductors have unique electronic properties and are important systems both at the f... more Organic semi-conductors have unique electronic properties and are important systems both at the fundamental level and also for their applications in electronic devices. In this article we focus on the particular case of rubrene which has one of the best electronic transport properties for application purposes. We show that this system can be well simulated by simple tight-binding systems representing one-dimensional (1D) chains that are weakly coupled to their neighboring chains in the same plane. This makes in principle this rubrene system somehow intermediate between 1D and isotropic 2D models. We analyse in detail the dc-transport and terahertz conductivity in the 1D and in the anisotropic 2D models. The transient localisation scenario allows us to reproduce satisfactorily some basics results such as mobility anisotropy and orders of magnitude as well as ac-conductivity in the terahertz range. This model shows in particular that even a weak inter-chain coupling is able to improve...
Using a low temperature Scanning Tunneling Microscope and a break-junction tunneling technique, t... more Using a low temperature Scanning Tunneling Microscope and a break-junction tunneling technique, the tunneling density of states (DOS) measurements on oxidized and bare surfaces of quasicrystalline icosahedral i-AlPdRe and i-AlCuFe, and of the approximant α-AlMnSi, as well as crystalline non-approximant ω-AlCuFe phase were performed. A narrow pseudogap at the Fermi level of about 50 meV width was found in tunneling spectra of icosahedral and approximant phases. For higher energies, the DOS exhibits a square root energy dependence attributed to electron–electron interaction effects. The tunneling DOS differs from the LMTO calculated DOS. The possible role of the electron scattering and the non-homogeneous electronic structure close to the surface are discussed.
We present a quantum formalism that provides a quantitative picture of the fundamental processes ... more We present a quantum formalism that provides a quantitative picture of the fundamental processes of charge separation that follow an absorption event. We apply the formalism to two-level photovoltaic cells and our purpose is to pedagogically explain the main aspects of the model. The formalism is developed in the energy domain and provides detailed knowledge about existence or absence of localized states and their effects on electronic structure and photovoltaic yield.
We present a generalization of a real-space method for solving the self-consistent field equation... more We present a generalization of a real-space method for solving the self-consistent field equations of the coherent potential approximation ͑CPA͒ for the case of multiplicative off-diagonal disorder originally proposed by Shiba. This generalization allows us to account for the difference in the bandwidths of the alloy-pure components in the study of the electronic properties of disordered alloys. The coherent potential and the Green function of the effective medium are expanded as continued fractions. It is shown that, contrary to the standard CPA method, the effective Hamiltonian is energy independent but acts in an augmented space, so that the recursion technique is directly applicable. This real-space approach opens up the possibility of studying the electronic structure properties of both chemically and topologically disordered alloys. Applications to the calculation of the density of states as well as to the study of stability of models and more realistic tight-binding Hamiltonians for binary transition-metal alloys are discussed.
... For the configuration entropy SCv(.x; a) per atom, we use the expression given by Kikuchi (1 ... more ... For the configuration entropy SCv(.x; a) per atom, we use the expression given by Kikuchi (1 974) in the pair approximation ... Anip is the charge relative to the pure material carried by the number of electrons in orbital p and site i. In the alloy, the number of electrons in orbital p and ...
A real-space approach based on the tight-binding approximation for studying electronic structure ... more A real-space approach based on the tight-binding approximation for studying electronic structure properties and stability and order in substitutional multicomponent alloys is presented. First, for a chemically random alloy based on a periodic lattice, we show that the coherent potential approximation equations can be solved self-consistently in real space with the same accuracy currently achieved in reciprocal space. The resulting one-electron Green function is given by a continued fraction expansion, and this analytic form can be conveniently used to determine alloy properties, and in particular the energetics. Second, combined with an orbitalpeeling technique, this method allows in a very efficient way the calculation of the effective cluster interactions which enter the expression of the configurational part of the total energy for describing order-disorder phenomena in alloys. Finally, we present some applications and briefly discuss the possible extensions of this approach. ͓S0163-1829͑97͒07028-8͔
Les effets d'hybridation sur la structure électronique des alliages métaux de transition-métaux p... more Les effets d'hybridation sur la structure électronique des alliages métaux de transition-métaux polyvalents sont étudiés à partir de la Cluster Bethe Lattice Méthode. Nous montrons que la densité d'états de ces alliages est caractérisée par la présence d'un pseudogap au sommet de la bande d. Leurs propriétés physiques sont discutées en relation avec l'existence de ce pseudogap.
... of energy. I Zm.) is centered at site R with angular momentum (L=l,m) and has its greatest co... more ... of energy. I Zm.) is centered at site R with angular momentum (L=l,m) and has its greatest contribution in sphere IL In this basis set, the Hamiltonian can he written as: -- ww ~ ~ t # --/2-#,-- Hgj.j L = CRL 01tL.RL + ARI. 31U.~ L ...
We study the electronic structure of two Dirac electron gazes coupled by a periodic Hamiltonian s... more We study the electronic structure of two Dirac electron gazes coupled by a periodic Hamiltonian such as it appears in rotated graphene bilayers. Ab initio and tight-binding approaches are combined and show that the spatially periodic coupling between the two Dirac electron gazes can renormalize strongly their velocity. We investigate in particular small angles of rotation and show that the velocity tends to zero in this limit. The localization is confirmed by an analysis of the eigenstates which are localized essentially in the AA zones of the Moire patterns.
The Editorial Board invites you to submit your letters to EPL EPL is a leading international jour... more The Editorial Board invites you to submit your letters to EPL EPL is a leading international journal publishing original, innovative Letters in all areas of physics, ranging from condensed matter topics and interdisciplinary research to astrophysics, geophysics, plasma and fusion sciences, including those with application potential. The high profile of the journal combined with the excellent scientific quality of the articles ensures that EPL is an essential resource for its worldwide audience. EPL offers authors global visibility and a great opportunity to share their work with others across the whole of the physics community.
The transport properties of MAPbI3 are analyzed within a tight-binding model. We find a strong Fr... more The transport properties of MAPbI3 are analyzed within a tight-binding model. We find a strong Fröhlich interaction of electron and holes with the electrostatic potential induced by the longitudinal optical phonon modes. This potential induces a strong scattering and limits the electronic mobilities at room temperature to about 200 cm 2 =V s. With additional extrinsic disorder, a large fraction of the electrons and holes are localized, but they can diffuse by following nearly adiabatically the evolution of the electrostatic potential. This process of diffusion, at a rate which is given by the lattice dynamics, contributes to the unique electronic properties of this material.
Stacking layered materials revealed to be a very powerful method to tailor their electronic prope... more Stacking layered materials revealed to be a very powerful method to tailor their electronic properties. It has indeed been theoretically and experimentally shown that twisted bilayers of graphene (tBLG) with a rotation angle θ, forming a Moiré pattern, confine electrons in a tunable way as a function of θ. Here, we study electronic structure and transport in tBLG using tight-binding numerical calculations in commensurate twisted bilayer structures and a pertubative continuous theory, which is valid for not-too-small angles (θ >∼ 2 •). These two approaches allow us to understand the effect of θ on the local density of states, the electron lifetime due to disorder, the DC conductivity, and the conductivity quantum correction due to multiple scattering effects. We distinguish the cases where disorder is equally distributed over two layers or only one layer. When only one layer is disordered, diffusion properties depend strongly on θ, thus showing the effect of Moiré electronic localization at intermediate angles θ , ∼2 • < θ <∼ 20 • .
Organic semi-conductors have unique electronic properties and are important systems both at the f... more Organic semi-conductors have unique electronic properties and are important systems both at the fundamental level and also for their applications in electronic devices. In this article we focus on the particular case of rubrene which has one of the best electronic transport properties for application purposes. We show that this system can be well simulated by simple tight-binding systems representing one-dimensional (1D) chains that are weakly coupled to their neighboring chains in the same plane. This makes in principle this rubrene system somehow intermediate between 1D and isotropic 2D models. We analyse in detail the dc-transport and terahertz conductivity in the 1D and in the anisotropic 2D models. The transient localisation scenario allows us to reproduce satisfactorily some basics results such as mobility anisotropy and orders of magnitude as well as ac-conductivity in the terahertz range. This model shows in particular that even a weak inter-chain coupling is able to improve...
Using a low temperature Scanning Tunneling Microscope and a break-junction tunneling technique, t... more Using a low temperature Scanning Tunneling Microscope and a break-junction tunneling technique, the tunneling density of states (DOS) measurements on oxidized and bare surfaces of quasicrystalline icosahedral i-AlPdRe and i-AlCuFe, and of the approximant α-AlMnSi, as well as crystalline non-approximant ω-AlCuFe phase were performed. A narrow pseudogap at the Fermi level of about 50 meV width was found in tunneling spectra of icosahedral and approximant phases. For higher energies, the DOS exhibits a square root energy dependence attributed to electron–electron interaction effects. The tunneling DOS differs from the LMTO calculated DOS. The possible role of the electron scattering and the non-homogeneous electronic structure close to the surface are discussed.
We present a quantum formalism that provides a quantitative picture of the fundamental processes ... more We present a quantum formalism that provides a quantitative picture of the fundamental processes of charge separation that follow an absorption event. We apply the formalism to two-level photovoltaic cells and our purpose is to pedagogically explain the main aspects of the model. The formalism is developed in the energy domain and provides detailed knowledge about existence or absence of localized states and their effects on electronic structure and photovoltaic yield.
We present a generalization of a real-space method for solving the self-consistent field equation... more We present a generalization of a real-space method for solving the self-consistent field equations of the coherent potential approximation ͑CPA͒ for the case of multiplicative off-diagonal disorder originally proposed by Shiba. This generalization allows us to account for the difference in the bandwidths of the alloy-pure components in the study of the electronic properties of disordered alloys. The coherent potential and the Green function of the effective medium are expanded as continued fractions. It is shown that, contrary to the standard CPA method, the effective Hamiltonian is energy independent but acts in an augmented space, so that the recursion technique is directly applicable. This real-space approach opens up the possibility of studying the electronic structure properties of both chemically and topologically disordered alloys. Applications to the calculation of the density of states as well as to the study of stability of models and more realistic tight-binding Hamiltonians for binary transition-metal alloys are discussed.
... For the configuration entropy SCv(.x; a) per atom, we use the expression given by Kikuchi (1 ... more ... For the configuration entropy SCv(.x; a) per atom, we use the expression given by Kikuchi (1 974) in the pair approximation ... Anip is the charge relative to the pure material carried by the number of electrons in orbital p and site i. In the alloy, the number of electrons in orbital p and ...
A real-space approach based on the tight-binding approximation for studying electronic structure ... more A real-space approach based on the tight-binding approximation for studying electronic structure properties and stability and order in substitutional multicomponent alloys is presented. First, for a chemically random alloy based on a periodic lattice, we show that the coherent potential approximation equations can be solved self-consistently in real space with the same accuracy currently achieved in reciprocal space. The resulting one-electron Green function is given by a continued fraction expansion, and this analytic form can be conveniently used to determine alloy properties, and in particular the energetics. Second, combined with an orbitalpeeling technique, this method allows in a very efficient way the calculation of the effective cluster interactions which enter the expression of the configurational part of the total energy for describing order-disorder phenomena in alloys. Finally, we present some applications and briefly discuss the possible extensions of this approach. ͓S0163-1829͑97͒07028-8͔
Les effets d'hybridation sur la structure électronique des alliages métaux de transition-métaux p... more Les effets d'hybridation sur la structure électronique des alliages métaux de transition-métaux polyvalents sont étudiés à partir de la Cluster Bethe Lattice Méthode. Nous montrons que la densité d'états de ces alliages est caractérisée par la présence d'un pseudogap au sommet de la bande d. Leurs propriétés physiques sont discutées en relation avec l'existence de ce pseudogap.
... of energy. I Zm.) is centered at site R with angular momentum (L=l,m) and has its greatest co... more ... of energy. I Zm.) is centered at site R with angular momentum (L=l,m) and has its greatest contribution in sphere IL In this basis set, the Hamiltonian can he written as: -- ww ~ ~ t # --/2-#,-- Hgj.j L = CRL 01tL.RL + ARI. 31U.~ L ...
We study the electronic structure of two Dirac electron gazes coupled by a periodic Hamiltonian s... more We study the electronic structure of two Dirac electron gazes coupled by a periodic Hamiltonian such as it appears in rotated graphene bilayers. Ab initio and tight-binding approaches are combined and show that the spatially periodic coupling between the two Dirac electron gazes can renormalize strongly their velocity. We investigate in particular small angles of rotation and show that the velocity tends to zero in this limit. The localization is confirmed by an analysis of the eigenstates which are localized essentially in the AA zones of the Moire patterns.
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Papers by Didier Mayou