In this paper, we study the quasiparticle scattering interference phenomenon in the presence of a single impurity within the renormalized Hubbard model. By calculating the energy and momentum dependence of the Fourier...In this paper, we study the quasiparticle scattering interference phenomenon in the presence of a single impurity within the renormalized Hubbard model. By calculating the energy and momentum dependence of the Fourier-transformed local density of states in the full Brillouin zone, we can qualitatively describe the main features of the quasiparticle scattering interference phenomenon in cuprate superconductors using a single point-like impurity. In particular, we show that with increasing energy, the position of the peak along the nodal （[0, 0] → [π, π]） direction moves steadily to a large momentum region, while the position of the peak along the antinodal （[0, 0] → [π, 0]） direction moves toward the center of the Brillouin zone.展开更多
We introduce local density of states in normal-conductor-superconductor compound systems and injectivity, emissivity to describe the transmission properties in these systems. Then we study the admittance of a one-chan...We introduce local density of states in normal-conductor-superconductor compound systems and injectivity, emissivity to describe the transmission properties in these systems. Then we study the admittance of a one-channel conductor which contains a scattering region and Andreev reflection with the discrete potential model and effective scattering approach.展开更多
The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. ...The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. The calculation of the local density of states shows that new states will emerge between the resonant Wannier-Stark states as a result of the intervention of time-dependent impurity potential, and the increase in electric field strength of impurity will result in the growing of the number of new states between the gaps of neighbouring Stark ladders.展开更多
We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light s...We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.展开更多
We study the local density of states （LDOS） for electrons scattering off the line edge of an atomic step defect on the surface of a three-dimensional （3D） topological insulator （TI） and the line edge of a finite...We study the local density of states （LDOS） for electrons scattering off the line edge of an atomic step defect on the surface of a three-dimensional （3D） topological insulator （TI） and the line edge of a finite 3D TI, where the front surface and side surface meet with different Fermi velocities, respectively. By using a S-function potential to model the edges, we find that the bound states existed along the step line edge significantly contribute to the LDOS near the edge, but do not modify the exponential behavior away from it. In addition, the power-law decaying behavior for LDOS oscillation away from the step is understood from the spin rotation for surface states scattering off the step defect with magnitude depending on the strength of the potential. Furthermore, the electron refraction and total reflection analogous to optics occurred at the line edge where two surfaces meet with different Fermi velocities, which leads to the LDOS decaying behavior in the greater Fermi velocity side similar to that for a step line edge. However, in the smaller velocity side the LDOS shows a different decaying behavior as x-1/2, and the wavevector of LDOS oscillation is no longer equal to the diameter of the constant energy contour of surface band, but is sensitively dependent on the ratio of the two Fermi velocities. These effects may be verified by STM measurement with high precision.展开更多
The local density of states （LDOS） of two-dimensional square lattice photonic crystal （PhC） defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point of...The local density of states （LDOS） of two-dimensional square lattice photonic crystal （PhC） defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point off the centre （for example, at the point （0.3a, 0.4a）, where a is the lattice constant） is extremely enhanced. Further, the disordered radii are introduced to imitate the real devices fabricated in our experiment, and then we study the LDOS of PhC cavity with configurations of different disordered radii. The results show that in the disordered cavity, the LDOS in the centre is still greatly reduced, while the LDOS at the point （0.3a, 0.4a） is still extremely enhanced. It shows that the LDOS analysis is useful. When a laser is designed on the basis of the square lattice PhC rod cavity, in order to enhance the spontaneous emission, the active materials should not be inserted in the centre of the cavity, but located at positions off the centre. So LDOS method gives a guide to design the positions of the active materials （quantum dots） in the lasers.展开更多
基金supported by the National Natural Science Foundation of China(20903075,21273172)Program of Introducing Talents of Discipline to Universities,China(111 Project)(B08040)Northwestern Polytechnical University Foundation for Fundamental Research,China(JC20100226)~~
基金supported by National Key R&D Program of China(Grant No.2022YFA1403201)National Natural Science Foundation of China(Grant No.12274205 and No.11874205).
基金This work was supported by the National Natural Science Foundation of China under Grant No. 10774082.
文摘In this paper, we study the quasiparticle scattering interference phenomenon in the presence of a single impurity within the renormalized Hubbard model. By calculating the energy and momentum dependence of the Fourier-transformed local density of states in the full Brillouin zone, we can qualitatively describe the main features of the quasiparticle scattering interference phenomenon in cuprate superconductors using a single point-like impurity. In particular, we show that with increasing energy, the position of the peak along the nodal （[0, 0] → [π, π]） direction moves steadily to a large momentum region, while the position of the peak along the antinodal （[0, 0] → [π, 0]） direction moves toward the center of the Brillouin zone.
文摘We introduce local density of states in normal-conductor-superconductor compound systems and injectivity, emissivity to describe the transmission properties in these systems. Then we study the admittance of a one-channel conductor which contains a scattering region and Andreev reflection with the discrete potential model and effective scattering approach.
基金Project supported by the Natural Science Foundation of Shanxi Province （Grant No 20031006）.
文摘The single-particle Green＇s function for a dc-biased superlattices with single impurity potential varying harmonically with time has been obtained in the framework of U（t,t＇） method and Floquet-Green＇s function. The calculation of the local density of states shows that new states will emerge between the resonant Wannier-Stark states as a result of the intervention of time-dependent impurity potential, and the increase in electric field strength of impurity will result in the growing of the number of new states between the gaps of neighbouring Stark ladders.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10674051 and 10811120010)the Program for Innovative Research Team of the Higher Education of Guangdong, China (Grant No 06CXTD005)
文摘We investigate numerically and experimentally the modification of the spontaneous emission rate for micrometersized light sources embedded in a hollow-core photonic crystal fiber （HCPCF）. The diameter of the light source is deliberately chosen such that they could be easily introduced into the central hole of the hollow-core photonic crystal fiber by capillary force. The photoluminescence from the microparticles is measured by using an inverted microscope in combination with a spectrometer. The modification of the spontaneous emission rate is observed in a wavelength region where there is no band gap. The experimental observations are consistent with the simulation results obtained by the plane wave expansion and finite-difference time-domain techniques.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274108)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20114306110008)the Hunan Provincial Innovation Foundation for Postgraduates(Grant No.CX2012B204)
文摘We study the local density of states （LDOS） for electrons scattering off the line edge of an atomic step defect on the surface of a three-dimensional （3D） topological insulator （TI） and the line edge of a finite 3D TI, where the front surface and side surface meet with different Fermi velocities, respectively. By using a S-function potential to model the edges, we find that the bound states existed along the step line edge significantly contribute to the LDOS near the edge, but do not modify the exponential behavior away from it. In addition, the power-law decaying behavior for LDOS oscillation away from the step is understood from the spin rotation for surface states scattering off the step defect with magnitude depending on the strength of the potential. Furthermore, the electron refraction and total reflection analogous to optics occurred at the line edge where two surfaces meet with different Fermi velocities, which leads to the LDOS decaying behavior in the greater Fermi velocity side similar to that for a step line edge. However, in the smaller velocity side the LDOS shows a different decaying behavior as x-1/2, and the wavevector of LDOS oscillation is no longer equal to the diameter of the constant energy contour of surface band, but is sensitively dependent on the ratio of the two Fermi velocities. These effects may be verified by STM measurement with high precision.
基金supported by the National Basic Research Program of China (Grant No. 2006CB921705)the National Natural Science Foundation of China (Grant Nos. 10634080,60677046 and 60838003)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z410 and 2007AA03Z408)
文摘The local density of states （LDOS） of two-dimensional square lattice photonic crystal （PhC） defect cavity is studied. The results show that the LDOS in the centre is greatly reduced, while the LDOS at the point off the centre （for example, at the point （0.3a, 0.4a）, where a is the lattice constant） is extremely enhanced. Further, the disordered radii are introduced to imitate the real devices fabricated in our experiment, and then we study the LDOS of PhC cavity with configurations of different disordered radii. The results show that in the disordered cavity, the LDOS in the centre is still greatly reduced, while the LDOS at the point （0.3a, 0.4a） is still extremely enhanced. It shows that the LDOS analysis is useful. When a laser is designed on the basis of the square lattice PhC rod cavity, in order to enhance the spontaneous emission, the active materials should not be inserted in the centre of the cavity, but located at positions off the centre. So LDOS method gives a guide to design the positions of the active materials （quantum dots） in the lasers.
