We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished, one is a spatially non-splittin...We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished, one is a spatially non-splitting zero bias peak, and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest vortices.Both of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields, implying an important role played by the vortex–vortex interactions. To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K. It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy, and the spatially evolved crossing features are related to the vortex–vortex interaction. The vortex core size under the zero-field limit is determined. These results provide a paradigm for studying the inherent vortex states of type-II superconductors especially based on an isolated vortex.展开更多
A scheme is proposed for preparing a quantum vortex state with a coupled waveguide, in which a single-mode odd cat state with weak intensity and a single-mode coherent state are inserted in the input ports, respective...A scheme is proposed for preparing a quantum vortex state with a coupled waveguide, in which a single-mode odd cat state with weak intensity and a single-mode coherent state are inserted in the input ports, respectively. The analytical wavefunction of the resulting state in the quadrature space is derived, and the vortex structure of the output state is analyzed. It is found that the obtained states, which may carry a vortex with topological charge index one, are entangled and nonclassical, depending only on the scaled propagation time and the weak intensity of the input odd cat state instead of the displacement parameter of the input coherent state. The phase distribution, however, in the quadrature space, depends on the displacement parameter of the input coherent state展开更多
Since the 1990s, the progress of nanofabrication technologies has resulted in increasing interests in the study of superconducting properties of mesoscopic samples. A mesoscopic sample has a size comparable to the coh...Since the 1990s, the progress of nanofabrication technologies has resulted in increasing interests in the study of superconducting properties of mesoscopic samples. A mesoscopic sample has a size comparable to the coherence length ξ and penetration depth λ. Properties of mesoscopic systems are considerably influenced by confinement effects. Therefore, the vortex state depends on the size and geometry of the sample.展开更多
A new kind of quantum non-Gaussian state with a vortex structure, termed a Bessel-Gaussian vortex state, is constructed, which is an eigenstate of the sum of squared annihilation operators a2 ＋ b2. The Wigner functio...A new kind of quantum non-Gaussian state with a vortex structure, termed a Bessel-Gaussian vortex state, is constructed, which is an eigenstate of the sum of squared annihilation operators a2 ＋ b2. The Wigner function of the quantum vortex state is derived and exhibits negativity which is an indication of nonclassicality. It is also found that a quantized vortex state is always in entanglement. And a scheme for generating such quantized vortex states is proposed.展开更多
We have theoretically studied the nucleation of superconductivity in doubly connected superconductors in the form of long superconducting cylinders. The giant vortex states are investigated with the nonlinear Ginzburg...We have theoretically studied the nucleation of superconductivity in doubly connected superconductors in the form of long superconducting cylinders. The giant vortex states are investigated with the nonlinear Ginzburg-Landau theory. The solutions of Ginzburg-Landau equations are solved numerically with relaxation method. The quantum size effect is clearly shown through the calculation of free energy.展开更多
An object or system is said to be chiral if it cannot be superimposed on its mirror reflection.Chirality is ubiquitous in nature,for example,in protein molecules and chiral phonons—acoustic waves carrying angular mom...An object or system is said to be chiral if it cannot be superimposed on its mirror reflection.Chirality is ubiquitous in nature,for example,in protein molecules and chiral phonons—acoustic waves carrying angular momentum—which are usually either intrinsically present or magnetically excited in suitable materials.Here,we report the use of intervortex forward Brillouin scattering to optically excite chiral flexural phonons in a twisted photonic crystal fiber,which is itself a chiral material capable of robustly preserving circularly polarized optical vortex states.The phonons induce a spatiotemporal rotating linear birefringence that acts back on the optical vortex modes,coupling them together.We demonstrate intervortex frequency conversion under the mediation of chiral flexural phonons and show that,for the same phonons,backward and forward intervortex conversion occurs at different wavelengths.The results open up,to our knowledge,new perspectives for Brillouin scattering and the chiral flexural phonons offer new opportunities for vortex-related information processing and multi-dimensional vectorial optical sensing.展开更多
The valley degree of freedom(DoF)plays a crucial role in valleytronics,paralleling the spin DoF in spintronics,and serves as a novel conduit for information and energy.In momentum space,valley DoF is characterized by ...The valley degree of freedom(DoF)plays a crucial role in valleytronics,paralleling the spin DoF in spintronics,and serves as a novel conduit for information and energy.In momentum space,valley DoF is characterized by discrete energy extremal states,which are present in conventional semiconductors and twodimensional(2D)crystal materials.Analogous wave behaviors in periodic structures allow for the application of valley dispersion relations to wave systems,including optics[1],acoustics[2,3],and water waves[4].When the wavelength is comparable to the period of an artificial crystal structure,classical waves experience strong Bragg scattering,resulting in a band gap and new propagation properties.Due to their macroscopic features and controllable geometric symmetry,these classical wave systems have become an ideal platform for studying topological physics.Although progress has been made in classical wave systems,conclusive evidence of topological valley states in water waves—a typical classical wave system—has not yet been obtained.展开更多
The evolution of a system state is derived based on the nonresonant interaction of a three-level ＂Λ＂ type atom with two cavity modes at a pair coherent state and two classic fields,and a cavity field state is analy...The evolution of a system state is derived based on the nonresonant interaction of a three-level ＂Λ＂ type atom with two cavity modes at a pair coherent state and two classic fields,and a cavity field state is analyzed in detail under conditional detecting.It is found that the quantized modified Bessel-Gaussian states as well as the superposition states consisting of the quantized vortex states with different weighted coefficients may be prepared through carefully preparing an initial atomic state and appropriately adjusting the interaction time.The scheme provides an additional choice to realize the two-mode quantized vortex state within the context of cavity quantum electrodynamics（QED）.展开更多
The Majorana fermions/quasi-particles obey non-Abelian statistics and play an essential role in topological quantum computing.Theoretically,they can be realized as a zero-energy excitation in the vortex core of topolo...The Majorana fermions/quasi-particles obey non-Abelian statistics and play an essential role in topological quantum computing.Theoretically,they can be realized as a zero-energy excitation in the vortex core of topological superconductors,called Majorana zero mode(MZM).However,the coexisting low-energy bound states in vortex cores often bring difficulties for identifying MZM.In this review,we summarized recent STM studies on the vortex states of electron-doped FeSe-based superconductors such as(Li,Fe)OHFeSe and single-layer FeSe/SrTiO_(3).Zero-bias conductance peaks(ZBCP)are observed in the unpinned vortex cores of(Li,Fe)OHFeSe.It displays nearly quantized conductance and distinct spatial distributions with respect to nonzero bound states,which indicates their nontrivial origin.Meanwhile,single-layer FeSe/SrTiO_(3)film only has conventional Caroli-de Gennes-Matricon(CdGM)bound states without zero-energy mode,reflecting the characteristics of s-wave superconductor.These results not only provide strong evidence of MZM,but also shed light on its origin in FeSe-based superconductors.展开更多
To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - t...To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - the Whirling Beam. The test results showed some unsteady aerodynamic behavior of the model rotor operating in the vortex-ring state. A very irregular variation of the rotortorque at low rate-of-descent was observed here for the first time. We considered it to be the start of the 'power settling' and determined the critical descent velocity according to this observation. A previous criterion for the vortex-ring state was modified to give a semi-empirical method for predicting the entire vortex-ring state boundary. The computed boundary shows a good correlation with the model test results and the flight experiences.展开更多
A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS ...A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.展开更多
基金Project supported by the National Key R&D Program of China (Grant No. 2022YFA1403203)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302802)+3 种基金the National Natural Science Foundation of China (Grant Nos. 12074002, 12374133, and 11804379)the Major Basic Program of Natural Science Foundation of Shandong Province (Grant No. ZR2021ZD01)the supports of the National Natural Science Foundation of China (Grant No. 12274001)the Natural Science Foundation of Anhui Province (Grant No. 2208085MA09)。
文摘We revisited the vortex states of 2H-NbSe_(2) towards zero fields by a low-temperature scanning tunneling microscope.Fine structures of the anisotropic vortex states were distinguished, one is a spatially non-splitting zero bias peak, and the other is an in-gap conductance anomaly resembling evolved crossing features around the center of the three nearest vortices.Both of them distribute solely along the next nearest neighboring direction of the vortex lattice and become unresolved in much higher magnetic fields, implying an important role played by the vortex–vortex interactions. To clarify these issues,we have studied the intrinsic vortex states of the isolated trapped vortex in zero fields at 0.45 K. It is concluded that the anisotropic zero bias peak is attributed to the superconducting gap anisotropy, and the spatially evolved crossing features are related to the vortex–vortex interaction. The vortex core size under the zero-field limit is determined. These results provide a paradigm for studying the inherent vortex states of type-II superconductors especially based on an isolated vortex.
文摘A scheme is proposed for preparing a quantum vortex state with a coupled waveguide, in which a single-mode odd cat state with weak intensity and a single-mode coherent state are inserted in the input ports, respectively. The analytical wavefunction of the resulting state in the quadrature space is derived, and the vortex structure of the output state is analyzed. It is found that the obtained states, which may carry a vortex with topological charge index one, are entangled and nonclassical, depending only on the scaled propagation time and the weak intensity of the input odd cat state instead of the displacement parameter of the input coherent state. The phase distribution, however, in the quadrature space, depends on the displacement parameter of the input coherent state
文摘Since the 1990s, the progress of nanofabrication technologies has resulted in increasing interests in the study of superconducting properties of mesoscopic samples. A mesoscopic sample has a size comparable to the coherence length ξ and penetration depth λ. Properties of mesoscopic systems are considerably influenced by confinement effects. Therefore, the vortex state depends on the size and geometry of the sample.
文摘A new kind of quantum non-Gaussian state with a vortex structure, termed a Bessel-Gaussian vortex state, is constructed, which is an eigenstate of the sum of squared annihilation operators a2 ＋ b2. The Wigner function of the quantum vortex state is derived and exhibits negativity which is an indication of nonclassicality. It is also found that a quantized vortex state is always in entanglement. And a scheme for generating such quantized vortex states is proposed.
基金The project supported by Natural Science Foundation from Beijing Normal University.Acknowledgments H. Zhao wishes to thank Profs. Fang-Lin Peng, Jue- Lian Shen, and Jia-Cai Nie for helpful discussions
文摘We have theoretically studied the nucleation of superconductivity in doubly connected superconductors in the form of long superconducting cylinders. The giant vortex states are investigated with the nonlinear Ginzburg-Landau theory. The solutions of Ginzburg-Landau equations are solved numerically with relaxation method. The quantum size effect is clearly shown through the calculation of free energy.
文摘An object or system is said to be chiral if it cannot be superimposed on its mirror reflection.Chirality is ubiquitous in nature,for example,in protein molecules and chiral phonons—acoustic waves carrying angular momentum—which are usually either intrinsically present or magnetically excited in suitable materials.Here,we report the use of intervortex forward Brillouin scattering to optically excite chiral flexural phonons in a twisted photonic crystal fiber,which is itself a chiral material capable of robustly preserving circularly polarized optical vortex states.The phonons induce a spatiotemporal rotating linear birefringence that acts back on the optical vortex modes,coupling them together.We demonstrate intervortex frequency conversion under the mediation of chiral flexural phonons and show that,for the same phonons,backward and forward intervortex conversion occurs at different wavelengths.The results open up,to our knowledge,new perspectives for Brillouin scattering and the chiral flexural phonons offer new opportunities for vortex-related information processing and multi-dimensional vectorial optical sensing.
基金sponsored by the National Natural Science Foundation of China(62475228 and 62275231)the Key Research and Development Program of the Ministry of Science and Technology(2022YFA1404704,2022YFA1405200 and 2022YFA1404902)+1 种基金the Key Research and Development Program of Zhejiang Province(2022C01036)the Fundamental Research Funds for the Central Universities。
文摘The valley degree of freedom(DoF)plays a crucial role in valleytronics,paralleling the spin DoF in spintronics,and serves as a novel conduit for information and energy.In momentum space,valley DoF is characterized by discrete energy extremal states,which are present in conventional semiconductors and twodimensional(2D)crystal materials.Analogous wave behaviors in periodic structures allow for the application of valley dispersion relations to wave systems,including optics[1],acoustics[2,3],and water waves[4].When the wavelength is comparable to the period of an artificial crystal structure,classical waves experience strong Bragg scattering,resulting in a band gap and new propagation properties.Due to their macroscopic features and controllable geometric symmetry,these classical wave systems have become an ideal platform for studying topological physics.Although progress has been made in classical wave systems,conclusive evidence of topological valley states in water waves—a typical classical wave system—has not yet been obtained.
文摘The evolution of a system state is derived based on the nonresonant interaction of a three-level ＂Λ＂ type atom with two cavity modes at a pair coherent state and two classic fields,and a cavity field state is analyzed in detail under conditional detecting.It is found that the quantized modified Bessel-Gaussian states as well as the superposition states consisting of the quantized vortex states with different weighted coefficients may be prepared through carefully preparing an initial atomic state and appropriately adjusting the interaction time.The scheme provides an additional choice to realize the two-mode quantized vortex state within the context of cavity quantum electrodynamics（QED）.
基金supported by the Innovation Program for Quantum Science and Technology(Grant no.2021ZD0302800)National Natural Science Foundation of China(Grants Nos.92065202,11888101,11790312,11961160717,12225403,12104094)+2 种基金Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01)Science and Technology Commission of Shanghai Municipality,China(Grant Nos.19JC1412702,21TQ1400100)the China Postdoctoral Science Foundation(Grant Nos.BX20200097,2020M681137).
文摘The Majorana fermions/quasi-particles obey non-Abelian statistics and play an essential role in topological quantum computing.Theoretically,they can be realized as a zero-energy excitation in the vortex core of topological superconductors,called Majorana zero mode(MZM).However,the coexisting low-energy bound states in vortex cores often bring difficulties for identifying MZM.In this review,we summarized recent STM studies on the vortex states of electron-doped FeSe-based superconductors such as(Li,Fe)OHFeSe and single-layer FeSe/SrTiO_(3).Zero-bias conductance peaks(ZBCP)are observed in the unpinned vortex cores of(Li,Fe)OHFeSe.It displays nearly quantized conductance and distinct spatial distributions with respect to nonzero bound states,which indicates their nontrivial origin.Meanwhile,single-layer FeSe/SrTiO_(3)film only has conventional Caroli-de Gennes-Matricon(CdGM)bound states without zero-energy mode,reflecting the characteristics of s-wave superconductor.These results not only provide strong evidence of MZM,but also shed light on its origin in FeSe-based superconductors.
文摘To understand the vortex-ring state and to develop an approach for predicting its boundary, a series of model rotor tests of vertical descent and oblique descent have been conducted on a newly-built test apparatus - the Whirling Beam. The test results showed some unsteady aerodynamic behavior of the model rotor operating in the vortex-ring state. A very irregular variation of the rotortorque at low rate-of-descent was observed here for the first time. We considered it to be the start of the 'power settling' and determined the critical descent velocity according to this observation. A previous criterion for the vortex-ring state was modified to give a semi-empirical method for predicting the entire vortex-ring state boundary. The computed boundary shows a good correlation with the model test results and the flight experiences.
基金the National Natural Science Foundation of China (Grant No. 11804154)the Scientific Research Foundation of NJIT (Grant Nos. YKJ201853 and CKJA201807)。
文摘A theoretical study on discrete vortex bound states is carried out near a vortex core in the presence of a van Hove singularity(VHS) near the Fermi level by solving Bogoliubov–de Gennes(Bd G) equations. When the VHS lies exactly at the Fermi level and also at the middle of the band, a zero-energy state and other higher-energy states whose energy ratios follow integer numbers emerge. These discrete vortex bound state peaks undergo a splitting behavior when the VHS or Fermi level moves away from the middle of the band. Such splitting behavior will eventually lead to a new arrangement of quantized vortex core states whose energy ratios follow half-odd-integer numbers.
