•LTO/STO ME coupling derives from ferroelectric and magnetic domain coupling.•ME coupling arising from Ti-O-Ti explains VO⋅ under tensile strain/ Eext→.•Dielectric constant of multiferroics affected ...by LTO/STO ME coupling and film-substrate mismatch.
This work focuses on LaTiO3 (LTO) thin films synthesized by the polymeric precursor method and deposited onto SrTiO3 (STO) substrates via spin coating. The results show interesting coexisting ferromagnetic (Mr≈2.85 emu/g) - ferroelectric (Pr≈18.5 μC/cm2) responses at room temperature. Magnetoelectric coupling can be observed under DC bias magnetic field (14 V/cm.Oe), and its dielectric constant is affected by the coupling between magnetic and electric dipoles at room temperature as well as oxygen octahedra distortion along direction a. Little film-substrate mismatch significantly influences the system dielectric properties. Our results suggest the possibility to induce ferromagnetic/ferroelectric phases in the LTO/STO heterojunctions using an electric/magnetic field, respectively, due to the magnetoelectric coupling. This study also helps comprehend oxygen vacancy dynamics when applying a tensile strain or an external electric field, which is fundamental for actuators, switches, magnetic field sensors, and new types of electronic memory devices.
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•New synthetic strategies to realize unusual Pd(III) state.•The weak ligand field and the triple hydrogen bond approaches.•Pd(III) appears in the halogen-bridged metal complexes.•Pd(III) state is ...realized even above room temperature.
The development of new halogen-bridged Pd chain complexes with molecular precision offers a promising strategy to stabilize Pd(III) ions, which are being considered as future optical, magnetic, dielectric, and conducting materials. More recently, uncommon and rare electronic states of Pd(III) ions in halogen-bridged chain complexes have been reported. In these systems, four different designed strategies have been adopted to stabilize Pd(III) oxidation states to date. This review focuses on the new strategies for the realization of Pd(III) halogen-bridged metal complexes (MX-Chains) using (1) weak ligand field and (2) triple hydrogen bond approaches. The resulting MX-Chains show clear evidence of the Pd(III) averaged-valence (AV) state rather than the conventional Pd(II)/Pd(IV) mixed-valence (MV) state. The relationships between the molecular structures, electronic states, and properties of these MX-Chains strongly depend on the in-plane ligands, counteranions and their surrounding environments. Furthermore, Pd(III) states have been found in the MX-Chains even above room temperature. Understanding and controlling the Pd(III) states in halogen-bridged chain complexes is a critical issue for development of next-generation devices, such as molecular electrical nano-wires. Overall, this review establishes halogen-bridged Pd(III) complexes as highly effective solid-state materials and provides detailed insight into their structure–property relationships, laying the groundwork for future developments in this new class of advanced materials.
Abstract
We investigated the superfluid Mott-insulator phase transition within an open coupled cavity optomagnonic array system. Based on the quasibosonic approach and employing perturbation ...approximation and mean-field theory, we obtain the time-dependent analytical superfluid order parameter. Our analysis revealed that dissipation induces decoherence within the system, while a strong magnon-cavity coupling enhances coherence significantly. Moreover, we explored the mechanisms by which increasing the magnon-cavity coupling strength drives the system towards the superfluid phase. The work holds significant guidance for the study of superfluidMott insulator phase transition under dissipative conditions, and providing a reliable reference for experimental implementation in open quantum systems.
Using ab initio calculations we reveal the nature of the insulating phase recently found experimentally in monolayer 1T-NbSe2. We find soft phonon modes in a large part of the Brillouin zone ...indicating the strong-coupling nature of a charge-density-wave instability. Structural relaxation of a supercell reveals a Star-of-David reconstruction with an energy gain of 60 meV per primitive unit cell. The band structure of the distorted phase exhibits a half-filled flat band which is associated with orbitals that are delocalized over several atoms in each Star of David. By including many-body corrections through a combined GW, hybrid-functional, and DMFT treatment, we find the flat band to split into narrow Hubbard bands. The lowest energy excitation across the gap turns out to be between itinerant Se-p states and the upper Hubbard band, determining the system to be a charge-transfer insulator. Combined hybrid-functional and GW calculations show that long-range interactions shift the Se-p states to lower energies. Thus, a delicate interplay of local and long-range correlations determines the gap nature and its size in this distorted phase of the monolayer 1T-NbSe2.
Effective nonmagnetic control of the spin structure is at the forefront of the study for functional quantum materials. This study demonstrates that, by applying anisotropic strain up to only 0.05%, ...the metamagnetic transition field of spin-orbit-coupled Mott insulator Sr2IrO4 can be in-situ modulated by almost 300%. Simultaneous measurements of resonant x-ray scattering and transport reveal that this drastic response originates from the complete strain-tuning of the transition between the spin-flop and spin-flip limits, and is always accompanied by large elasto- and magneto-conductance. This enables electrically controllable and electronically detectable metamagnetic switching, despite the antiferromagnetic insulating state. The obtained strain-magnetic field phase diagram reveals that C4-symmetry-breaking anisotropy is introduced by strain via pseudospin-lattice coupling, directly demonstrating the pseudo-Jahn-Teller effect of spin-orbit-coupled complex oxides. The extracted coupling strength is much weaker than the superexchange interactions, yet crucial for the spontaneous symmetry-breaking, affording the remarkably efficient strain-control.
We study the many-body instabilities of correlated electrons on the half-filled honeycomb lattice with enhanced exchange coupling. The system is described by an extended Hubbard model including the ...next-nearest-neighbor Coulomb repulsion (V2) and the nearest-neighbor exchange interaction (J). We use the truncated unity functional renormalization group approach to determine a schematic ground-state phase diagram with higher resolution in the parameter space of V2 and J. In the absence of the on-site repulsion and presence of sizable next-nearest-neighbor repulsion and enhanced nearest-neighbor exchange interaction, we encounter the quantum spin Hall phase, the spin-Kekulé phase, and the three-sublattice and the incommensurate charge-density-wave phases. We propose a scheme for combining consistently the truncated unity functional renormalization group and the mean-field approximation, which is distinct from the conventional one that directly uses the renormalization-group results as an input for the mean-field calculation. This scheme is used to study in detail the quantum spin Hall phase, presenting some characteristics like the bulk gap, the Chern number and the helical edge states.
•A Phase diagram of half-filled honeycomb lattice is presented with higher resolution.•Novel scheme for linking the truncated unity FRG with the mean-field theory is proposed.•Quantitative analysis of quantum spin Hall phase induced by exchange interaction is provided.•Induced QSH phase may have a bulk gap much larger than those of typical 2D topological insulators.
Members of a recently discovered class of two-dimensional materials based on transition metal phosphorous trichalcogenides exhibit an antiferromagnetic ground state and they have potential ...applications in spintronics. In particular, FePS3 is a Mott insulator with a band gap of ∼ 1.5 eV. In this study, we used Raman spectroscopy and first-principles density functional theoretical analysis to examine the stability of the structure and electronic properties of FePS3 under pressure. Raman spectroscopy detected two phase transitions at 4.6 GPa and 12 GPa, which were characterized by changes in the pressure coefficients of the mode frequencies and the number of symmetry allowed modes. FePS3 transformed from the ambient monoclinic C2/m phase with a band gap of 1.54 eV to another monoclinic C2/m (band gap of 0.1 eV) phase at 4.6 GPa, which was followed by another transition to the metallic trigonal P-31m phase at 12 GPa. Our findings complement those obtained recently in high pressure X-ray diffraction studies. The calculated elastic properties indicated increases in the bulk, shear, and Young's moduli, as well as a significant reduction in the universal elastic anisotropy index as the crystal changed from the ambient monoclinic C2/m phase to the high pressure trigonal P-31m phase.
•In-situ Raman spectroscopy conducted for bulk FePS3 for pressures up to 19 GPa.•Two structural transitions observed at 4.6 GPa and 12 GPa.•Calculations indicated a significant band gap reduction across the first transition.•Second transition indicated the appearance of a metallic trigonal phase.•Raman mode near 379 cm−1 exhibited anomalous peak sharpening.
We study the single-band one-dimensional Hubbard model in an arbitrary magnetic field using the cumulant Green's functions method (CGFM) with clusters containing 5, 6, 7, and 8 sites. We calculate ...the occupation numbers as functions of the chemical potential in a positive magnetic field and identify a partially filled region with negative magnetization. We obtain the ground-state phase diagram in chemical potential vs. magnetic field coordinates. We include a straightforward application of the CGFM by using a cluster as a correlated quantum dot connected to correlated leads to construct a single-electron transistor that presents a spin-polarised conductance.
•We implement the cumulant Green's functions method for nonzero magnetic field.•We find a small-size effect (negative magnetization in low positive magnetic fields).•We recover the phase diagram of the 1D Hubbard model in a positive magnetic field.•We calculate the transport through a quantum wire and obtain spin-polarised currents.
Microscopically visualizing the evolution of electronic structures at the interface between two electron-correlated domains shows fundamental importance in both material science and physics. Here, we ...report scanning tunneling microscopy and spectroscopy studies of the interfacial electronic structures evolution in a phase-engineered monolayer NbSe2 heterostructure. The H-NbSe2 metallic state penetrates the Mott insulating T-NbSe2 at the H/T phase interface, with a prominent 2D charge density wave (CDW) proximity effect. Moreover, an insulating Mott gap collapse with the disappearance of the upper Hubbard band is detected at the electronic phase transition region. Theoretical calculations reveal that such insulating Mott gap collapse can be attributed to the electron doping effect induced by the interface. Our findings promote a microscopical understanding of the interactions between different electron-correlated systems and provide an effective method for controlling the Mott insulating states with phase engineering.
Due to the coexistence of spin-orbital coupling (SOC) and electron correlation interactions, double perovskite iridates are considered ideal material to investigate the Mott insulating states and ...Kitaev interactions. In this work, we studied the spin-orbital coupling (SOC), spin-phonon coupling (SPC), and Kitaev magnetism in antiferromagnetic La2ZnIrO6 single crystal by magnetometer and Raman scattering spectroscopy measurements. Based on the temperature dependence of the magnetization under different magnetic fields, we found that all the initial temperatures of the paramagnetic-ferromagnetic transition were basically concentrated around 8.8 K, while the temperature of ferromagnetic-antiferromagnetic transition continued to decrease from 7 K to 2 K. Anomalous modes of frequency softening at magnetic-order temperature were detected from the polarized Raman scattering spectra, indicating the presence of strong spin-phonon coupling and Kitaev interaction in La2ZnIrO6.
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