The electronic evolution of Mott insulators into exotic correlated phases remains puzzling,because of electron interaction and inhomogeneity.Introduction of individual imperfections in Mott insulators could help captu...The electronic evolution of Mott insulators into exotic correlated phases remains puzzling,because of electron interaction and inhomogeneity.Introduction of individual imperfections in Mott insulators could help capture the main mechanism and serve as a basis to understand the evolution.Here we utilize scanning tunneling microscopy to probe the atomic scale electronic structure of the spin-orbit-coupling assisted Mott insulator Sr_(3)Ir_(2)O_(7).It is found that the tunneling spectra exhibit a homogeneous Mott gap in defect-free regions,but near the oxygen vacancy in the rotated Ir O_(2)plane the local Mott gap size is significantly enhanced.We attribute the enhanced gap to the locally reduced hopping integral between the 5d electrons of neighboring Ir sites via the bridging planar oxygen p orbitals.Such bridging defects have a dramatic influence on local bandwidth,thus provide a new way to manipulate the strength of Mottness in a Mott insulator.展开更多
We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the F...We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the Fermi energy with increasing temperature, while the charge transfer band remains basically unchanged. This leads to a reduction of the charge transfer gap size at high temperatures, and the rate of reduction is much faster than that of conventional semiconductors. Across the Neel temperature for antiferromagnetic order, there is no sudden change in the electronic structure. These results shed new light on the theoretical models about the parent Mott insulator of cuprates.展开更多
We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach...We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach each other,the transfer of spectral weight from high energy Hubbard band to low energy ingap state creates a broad peak and nearly V-shaped gap around the Fermi level.The peak position shows a sudden drop at distance around 4 a_(0)and then remains almost constant.The in-gap states exhibit peculiar spatial distributions depending on the configuration of the two dopants relative to the underlying Cu lattice.These results shed important new lights on the evolution of low energy electronic states when a few holes are doped into parent cuprates.展开更多
Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the pla...Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent dI/dV spectroscopy measurements on 2H-NbSe_(2) under different field orientations.We observe characteristic kink features for weak in-plane magnetic fields,but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values.Especially,the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe_(2) in the presence of magnetic field.展开更多
基金the National Key R&D Program of China(Grant No.2017YFA0302900)the Basic Science Center Project of National Natural Science Foundation of China(Grant No.51788104)+4 种基金supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC)Open Research Fund Program of the State Key Laboratory of Low-Dimensional Quantum Physicssupported by the National Natural Science Foundation of China(Grant No.12074424)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China。
文摘The electronic evolution of Mott insulators into exotic correlated phases remains puzzling,because of electron interaction and inhomogeneity.Introduction of individual imperfections in Mott insulators could help capture the main mechanism and serve as a basis to understand the evolution.Here we utilize scanning tunneling microscopy to probe the atomic scale electronic structure of the spin-orbit-coupling assisted Mott insulator Sr_(3)Ir_(2)O_(7).It is found that the tunneling spectra exhibit a homogeneous Mott gap in defect-free regions,but near the oxygen vacancy in the rotated Ir O_(2)plane the local Mott gap size is significantly enhanced.We attribute the enhanced gap to the locally reduced hopping integral between the 5d electrons of neighboring Ir sites via the bridging planar oxygen p orbitals.Such bridging defects have a dramatic influence on local bandwidth,thus provide a new way to manipulate the strength of Mottness in a Mott insulator.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0302900)the Basic Science Center Project of the National Natural Science Foundation of China (Grant No. 51788104)supported in part by the Beijing Advanced Innovation Center for Future Chip (ICFC)。
文摘We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca_(3)Cu_(2)O_(4)Cl_(2) parent Mott insulator of cuprates. It is found that the upper Hubbard band moves towards the Fermi energy with increasing temperature, while the charge transfer band remains basically unchanged. This leads to a reduction of the charge transfer gap size at high temperatures, and the rate of reduction is much faster than that of conventional semiconductors. Across the Neel temperature for antiferromagnetic order, there is no sudden change in the electronic structure. These results shed new light on the theoretical models about the parent Mott insulator of cuprates.
基金the National Program on Key Basic Research Project of China(973 Program)(2017YFA0302900)the Basic Science Center Project of the National Natural Science Foundation of China(51788104)supported in part by the Beijing Advanced Innovation Center for Future Chip(ICFC)。
文摘We use scanning tunneling microscopy to visualize the atomic-scale electronic states induced by a pair of hole dopants in Ca_(2)CuO_(2)Cl_(2)parent Mott insulator of cuprates.We find that when the two dopants approach each other,the transfer of spectral weight from high energy Hubbard band to low energy ingap state creates a broad peak and nearly V-shaped gap around the Fermi level.The peak position shows a sudden drop at distance around 4 a_(0)and then remains almost constant.The in-gap states exhibit peculiar spatial distributions depending on the configuration of the two dopants relative to the underlying Cu lattice.These results shed important new lights on the evolution of low energy electronic states when a few holes are doped into parent cuprates.
基金supported by the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302502)funding provided by Shanghai Jiao Tong University.
文摘Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations,due to their distinct vortex structures and upper critical field values.Here,we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent dI/dV spectroscopy measurements on 2H-NbSe_(2) under different field orientations.We observe characteristic kink features for weak in-plane magnetic fields,but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values.Especially,the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe_(2) in the presence of magnetic field.
