Entanglement of charge orderings and other electronic orders such as superconductivity is in the core of challenging physics issues of complex materials including high temperature superconductivity. ...Here, we report on the observation of a unique nanometer scale honeycomb charge ordering of the cleaved IrTe2 surface, which hosts a superconducting state. IrTe2 was recently established to exhibit an intriguing cascade of stripe charge orders. The stripe phases coexist with a hexagonal phase, which is formed locally and falls into a superconducting state below 3 K. The atomic and electronic structures of the honeycomb and hexagon pattern of this phase are consistent with the charge order nature, but the superconductivity does not survive on neighboring stripe charge order domains. The present work provides an intriguing physics issue and a new direction of functionalization for two-dimensional materials.
Charge ordering in superconducting copper oxides Frano, Alex; Blanco-Canosa, Santiago; Keimer, Bernhard ...
Journal of physics. Condensed matter,
2020-Jun-18, Volume:
32, Issue:
37
Journal Article
Peer reviewed
Open access
Charge order has recently been identified as a leading competitor of high-temperature superconductivity in moderately doped cuprates. We provide a survey of universal and materials-specific aspects ...of this phenomenon, with emphasis on results obtained by scattering methods. In particular, we discuss the structure, periodicity, and stability range of the charge-ordered state, its response to various external perturbations, the influence of disorder, the coexistence and competition with superconductivity, as well as collective charge dynamics. In the context of this journal issue which honors Roger Cowley's legacy, we also discuss the connection of charge ordering with lattice vibrations and the central-peak phenomenon. We end the review with an outlook on research opportunities offered by new synthesis methods and experimental platforms, including cuprate thin films and superlattices.
X-ray techniques have been used for more than a century to study the atomic and electronic structure in practically any type of material. The advent of correlated electron systems, in particular ...complex oxides, brought about new scientific challenges and opportunities for the advancement of conventional X-ray methods. In this context, the need for new approaches capable of selectively sensing new forms of orders involving all degrees of freedom-charge, orbital, spin, and lattice-paved the way for the emergence and success of resonant X-ray scattering, which has become an increasingly popular and powerful tool for the study of electronic ordering phenomena in solids. We review the recent resonant X-ray scattering breakthroughs in the copper oxide high-temperature superconductors, in particular regarding the phenomenon of charge order, a broken-symmetry state occurring when valence electrons self-organize into periodic structures. After a brief historical perspective on charge order, we outline the milestones in the development of resonant X-ray scattering as well as the basic theoretical formalism underlying its unique capabilities. The rest of the review focuses on the recent contributions of resonant scattering to the advancements in our description and understanding of charge order. To conclude, we propose a series of present and upcoming challenges and discuss the future outlook for this technique.
We investigate the effect of uniaxial heterostrain on the interacting phase diagram of magic-angle twisted bilayer graphene. Using both self-consistent Hartree-Fock and density-matrix renormalization ...group calculations, we find that small strain values (ε ∼ 0.1 % – 0.2 %) drive a zero-temperature phase transition between the symmetry-broken "Kramers intervalley-coherent" insulator and a nematic semimetal. The critical strain lies within the range of experimentally observed strain values, and we therefore predict that strain is at least partly responsible for the sample-dependent experimental observations.
In the work, we investigated a generalized model of the fermionic lattice gas in the form of the extended Hubbard model with intersite Ising-like interactions (between nearest neighbors, both ...antiferromagnetic and ferromagnetic) at the atomic limit on the triangular lattice. In the ground state, we find the exact phase diagram as a function of μ. Within the mean-field decoupling of the intersite term and exact treatment of onsite interaction, we found also the diagrams for T≥0 including metastable phases. For antiferromagnetic coupling, we find that nontrival ordered phase can exist with coexistence of charge and metamagnetic ordering. The transition between the ordered phase and the nonordered phase can be discontinuous as well continuous depending on the model parameters. Moreover, the ordered phase can coexist with the nonordered phase in phase separated states for fixed electron concentration. Additionally, the ranges of phases metastability are determined in the neighborhood of the discontinuous transitions.
•The extended Hubbard model with intersite Ising-like interactions is investigated.•Orderings on the triangular lattice with geometrical frustration are analyzed.•The exact ground state for fixed chemical potential is determined.•Mean-field field solutions of the model for finite temperatures are found and discussed.•Complex phase diagrams for both signs of magnetic interactions are determined.
The Fe intercalated transition metal dichalcogenide (TMD), Fe1/3NbS2, exhibits remarkable resistance switching properties and highly tunable spin ordering phases due to magnetic defects. We conduct ...synchrotron x-ray scattering measurements on both underintercalated ( x = 0.32 ) and overintercalated ( x = 0.35 ) samples. We discover a new charge order phase in the overintercalated sample, where the excess Fe atoms lead to a zigzag antiferromagnetic order. The agreement between the charge and magnetic ordering temperatures, as well as their intensity relationship, suggests a strong magnetoelastic coupling as the mechanism for the charge ordering. In conclusion, our results reveal the first example of a charge order phase among the intercalated TMD family and demonstrate the ability to stabilize charge modulation by introducing electronic correlations, where the charge order is absent in bulk 2H - NbS2 compared to other pristine TMDs.
In this paper, the structure and properties of the $1{\mathbin:}1$ superlattice of ${\mathrm{LaVO}}_{3}$ and ${\mathrm{SrVO}}_{3}$ are investigated with a first-principles ...density-functional-theory-plus-$U$ ($\mathrm{DFT}+U$) method. The lowest energy states are antiferromagnetic charge-ordered Mott-insulating phases. In one of these insulating phases, layered charge ordering combines with the layered La/Sr cation ordering to produce a polar structure with a large nonzero spontaneous polarization normal to the interfaces. This polarization, comparable to that of conventional ferroelectrics, is produced by electron transfer between the ${\mathrm{V}}^{3+}$ and ${\mathrm{V}}^{4+}$ layers. The energy of this normal-polarization state relative to the ground state is only 3 meV per vanadium. Under tensile strain, this energy difference can be further reduced, suggesting that the normal-polarization state can be induced by an electric field applied normal to the superlattice layers, yielding an antiferroelectric double-hysteresis loop. Finally, if the system does not switch back to the ground state on removal of the field, a ferroelectric-type hysteresis loop could be observed.
PDF
