It is well-known that in bulk, the solution of the Bogoliubov-de Gennes equations is the same whe... more It is well-known that in bulk, the solution of the Bogoliubov-de Gennes equations is the same whether or not the Hartree-Fock term is included. In this case the Hartree-Fock potential is position independent and, so, gives the same contribution to both the single-electron energies and the Fermi level (the chemical potential). Thus, the single-electron energy measured from the Fermi level (it controls the solution) stays the same. It is not the case for nanostructured superconductors, where quantum confinement breaks the translational symmetry and results in a position dependent Hartree-Fock potential. Now the contribution of the Hartree-Fock mean field to the single-electron energies depends on the relevant quantum numbers. Moreover, the single-electron wave functions can be influenced by the presence of this additional spatially dependent field. We numerically solved the Bogoliubov-de Gennes equations with the Hartree-Fock term for a clean metallic nanocylinder and found a shift of...
Abstract By numerically solving the Bogoliubov-de Gennes equations, Friedel oscillations of singl... more Abstract By numerically solving the Bogoliubov-de Gennes equations, Friedel oscillations of single quasiparticles in nanoscale superconducting square disks are systematically studied. We find that Anderson's approximation, which assumes the electron- and hole-like wave functions of a quasiparticle are proportional to a certain single-electron wave function, breaks down under strong quantum confinement, i.e. the electron- and hole-like components of single quasiparticles may show Friedel oscillations with different amplitude and normalized profile, especially when the corresponding single-electron energy moves away from the Fermi level. Such oscillation behavior is referred as dual Friedel oscillations of single quasiparticles, and is expected to be observed the local density of states spectrum. The resulting density of states (DOS) becomes asymmetric and shows significant oscillations with respect to the applied bias.
In this paper, we introduce a small molecule-acetylacetone into perovskite precursor to adjust th... more In this paper, we introduce a small molecule-acetylacetone into perovskite precursor to adjust the crystallinity of the perovskite film. Through experiments, we found that acetylacetone not only effectively increase the coverage of perovskite films, but also significantly increase the crystallinity of perovskite crystals and reduce the residual of the solvent in the process of preparing perovskite crystals. As a result, the performance of device treated by the 28 ul ml−1 acetylacetone achieved a summit PCE of 15.29%, which demonstrated a 17.43% increase compared with the PCE of 13.02% of the original device.
Journal of physics. Condensed matter : an Institute of Physics journal, 2015
Since the 1960's it has been well known that the basic superconductive quantities can exhibit... more Since the 1960's it has been well known that the basic superconductive quantities can exhibit oscillations as functions of the thickness (diameter) in superconducting nanofilms (nanowires) due to the size quantization of the electronic spectrum. However, very little is known about the effects of quantum confinement on the microscopic properties of vortices. Based on a numerical solution to the Bogoliubov-de Gennes equations, we study the quantum-size oscillations of the vortex core resulting from the sequential interchange of the Kramer-Pesch and anti-Kramer-Pesch regimes with changing nanocylinder radius. The physics behind the anti-Kramer-Pesch anomaly is displayed by utilizing a semi-analytical Anderson approximate solution. We also demonstrate that the anti-Kramer-Pesch vortex core is robust against thermal smearing and results in a distinctive two-maxima structure in the local density of states, which can be used to identify the existence of the anti-Kramer-Pesch vortex.
It is well-known that in bulk, the solution of the Bogoliubov-de Gennes equations is the same whe... more It is well-known that in bulk, the solution of the Bogoliubov-de Gennes equations is the same whether or not the Hartree-Fock term is included. In this case the Hartree-Fock potential is position independent and, so, gives the same contribution to both the single-electron energies and the Fermi level (the chemical potential). Thus, the single-electron energy measured from the Fermi level (it controls the solution) stays the same. It is not the case for nanostructured superconductors, where quantum confinement breaks the translational symmetry and results in a position dependent Hartree-Fock potential. Now the contribution of the Hartree-Fock mean field to the single-electron energies depends on the relevant quantum numbers. Moreover, the single-electron wave functions can be influenced by the presence of this additional spatially dependent field. We numerically solved the Bogoliubov-de Gennes equations with the Hartree-Fock term for a clean metallic nanocylinder and found a shift of...
Abstract By numerically solving the Bogoliubov-de Gennes equations, Friedel oscillations of singl... more Abstract By numerically solving the Bogoliubov-de Gennes equations, Friedel oscillations of single quasiparticles in nanoscale superconducting square disks are systematically studied. We find that Anderson's approximation, which assumes the electron- and hole-like wave functions of a quasiparticle are proportional to a certain single-electron wave function, breaks down under strong quantum confinement, i.e. the electron- and hole-like components of single quasiparticles may show Friedel oscillations with different amplitude and normalized profile, especially when the corresponding single-electron energy moves away from the Fermi level. Such oscillation behavior is referred as dual Friedel oscillations of single quasiparticles, and is expected to be observed the local density of states spectrum. The resulting density of states (DOS) becomes asymmetric and shows significant oscillations with respect to the applied bias.
In this paper, we introduce a small molecule-acetylacetone into perovskite precursor to adjust th... more In this paper, we introduce a small molecule-acetylacetone into perovskite precursor to adjust the crystallinity of the perovskite film. Through experiments, we found that acetylacetone not only effectively increase the coverage of perovskite films, but also significantly increase the crystallinity of perovskite crystals and reduce the residual of the solvent in the process of preparing perovskite crystals. As a result, the performance of device treated by the 28 ul ml−1 acetylacetone achieved a summit PCE of 15.29%, which demonstrated a 17.43% increase compared with the PCE of 13.02% of the original device.
Journal of physics. Condensed matter : an Institute of Physics journal, 2015
Since the 1960's it has been well known that the basic superconductive quantities can exhibit... more Since the 1960's it has been well known that the basic superconductive quantities can exhibit oscillations as functions of the thickness (diameter) in superconducting nanofilms (nanowires) due to the size quantization of the electronic spectrum. However, very little is known about the effects of quantum confinement on the microscopic properties of vortices. Based on a numerical solution to the Bogoliubov-de Gennes equations, we study the quantum-size oscillations of the vortex core resulting from the sequential interchange of the Kramer-Pesch and anti-Kramer-Pesch regimes with changing nanocylinder radius. The physics behind the anti-Kramer-Pesch anomaly is displayed by utilizing a semi-analytical Anderson approximate solution. We also demonstrate that the anti-Kramer-Pesch vortex core is robust against thermal smearing and results in a distinctive two-maxima structure in the local density of states, which can be used to identify the existence of the anti-Kramer-Pesch vortex.
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Papers by Yajiang Chen