Imaging the atomic-scale electronic states induced by a pair of hole dopants in Ca2CuO2Cl2 Mott insulator

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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 use scanning tunneling microscopy to probe the atomic scale electronic structure of the spin-orbit-coupling assisted Mott insulator Sr3Ir2O7. We find that the tunneling spectra exhibit a homogeneous Mott gap in defect-free regions, but near the oxygen vacancy in the rotated IrO2 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.

contrasting

confidence: 79%

Tuning the Mottness in Sr₃Ir₂O₇ via Bridging Oxygen Vacancies

Zou

Gong

et al. 2023

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“…In contrast, the decrease of the spectrum weight is observed at the Ca vacancy with hole doping, which is consistent with a previous report. [46] Therefore, we conclude that the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. We believe the electron doping will systematically change the spectral function and the superexchange 𝐽 values, thus leading to a complex modification of the whole electronic state.…”

mentioning

confidence: 76%

“…As a matter of fact, the feature of the unconventional in-gap state induced by Ca vacancy is quite similar with the previous report. [46] We note that there is a theoretical calculation concerning repulsive impurity potential that try to explain this unconventional in-gap state. [34] However, to unravel the origin of the Ca vacancy induced in-gap state may require further theoretical studies.…”

mentioning

confidence: 98%

Mott Gap Filling by Doping Electrons through Depositing One Sub-Monolayer Thin Film of Rb on Ca₂CuO₂Cl₂

Li 李,

Wang 王,

Fan 范

et al. 2024

Understanding the doping evolution from a Mott insulator to a superconductor probably holds the key to resolve the mystery of unconventional superconductivity in copper oxides. To elucidate the evolution of the electronic state starting from the Mott insulator, we dose the surface of the parent phase Ca2CuO2Cl2 by depositing Rb atoms, which are supposed to donate electrons to the CuO2 planes underneath. We successfully achieved the Rb sub-monolayer thin films in forming the square lattice. The scanning tunneling microscopy or spectroscopy measurements on the surface show that the Fermi energy is pinned within the Mott gap but close to the edge of the charge transfer band. In addition, an in-gap state appears at the bottom of the upper Hubbard band (UHB), and the Mott gap will be significantly diminished. Combined with the Cl defect and the Rb adatom/cluster results, the electron doping is likely to increase the spectra weight of the UHB for the double occupancy. Our results provide information to understand the electron doping to the parent compound of cuprates.

“…2(a). It can be seen that the spectral lineshapes are highly analogous to each other, but the positions of the two band edges fluctuate slightly in space due to the unavoidable defects that are several lattice constants away [22] or even in the underneath layers. To determine the size of the CTG, we extract the UHB and CTB band edge energies for each 𝑑𝐼/𝑑𝑉 spectrum, as illustrated in Fig.…”

mentioning

confidence: 95%

Temperature Dependence of the Electronic Structure of Ca₃Cu₂O₄Cl₂ Mott Insulator

Li¹,

Ye²,

Zhao³

et al. 2022

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We use scanning tunneling microscopy to study the temperature evolution of electronic structure in Ca3Cu2O4Cl2 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.