Strain-engineering Mott-insulating La2CuO4

Ivashko, Oleh; Horio, M.; Wan, Wenjie; Christensen, Niels Bech; McNally, Daniel; Paris, E.; Tseng, Yi; Shaik, N. E.; Rønnow, Henrik M.; Wei, Haofei I.; Adamo, Carolina; Lichtensteiger, Céline; Gibert, Marta; Beasley, M. R.; Shen, Kyle; Tomczak, Jan M.; Schmitt, Thorsten; Chang, J.

doi:10.1038/s41467-019-08664-6

Cited by 46 publications

(32 citation statements)

References 51 publications

(72 reference statements)

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“…An anisotropic response of the magnetic excitations is reminiscent of electron doping, affecting mainly the [h,h] direction in La-doped Sr 2 IrO 4 (38,40,46) and Sr 3 Ir 2 O 7 (45,47). It is worth noting that the present anisotropic evolution is dissimilar to the case of a Mott insulator such as La 2 CuO 4 , in which epitaxial strain affects the magnetic dispersion in a similar way along the nodal and antinodal directions (51). As summarized in Fig.…”

Section: Resultsmentioning

confidence: 76%

Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄

Paris

Tseng

Pärschke

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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In the high spin–orbit-coupled Sr2IrO4, the high sensitivity of the ground state to the details of the local lattice structure shows a large potential for the manipulation of the functional properties by inducing local lattice distortions. We use epitaxial strain to modify the Ir–O bond geometry in Sr2IrO4 and perform momentum-dependent resonant inelastic X-ray scattering (RIXS) at the metal and at the ligand sites to unveil the response of the low-energy elementary excitations. We observe that the pseudospin-wave dispersion for tensile-strained Sr2IrO4 films displays large softening along the [h,0] direction, while along the [h,h] direction it shows hardening. This evolution reveals a renormalization of the magnetic interactions caused by a strain-driven cross-over from anisotropic to isotropic interactions between the magnetic moments. Moreover, we detect dispersive electron–hole pair excitations which shift to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. This behavior shows an intimate coupling between charge excitations and lattice distortions in Sr2IrO4, originating from the modified hopping elements between the t2g orbitals. Our work highlights the central role played by the lattice degrees of freedom in determining both the pseudospin and charge excitations of Sr2IrO4 and provides valuable information toward the control of the ground state of complex oxides in the presence of high spin–orbit coupling.

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Section: Resultsmentioning

confidence: 76%

Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄

Paris

Tseng

Pärschke

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…Indeed, (ii) a somewhat smaller ratio U/t would imply a larger T c at fixed t [33]. Since the interaction U is local, it typically varies much more slowly when, for example, applying compressive strain or pressure and can be assumed to be constant as a first approximation (for secondary effects, see [81,82]). Thus, compressive strain or pressure enhance (i) t and reduce (ii) U/t.…”

Section: Non-local Correlations and Superconducting Phase Diagrammentioning

confidence: 99%

Phase Diagram of Nickelate Superconductors Calculated by Dynamical Vertex Approximation

Held

Worm

et al. 2022

Front. Phys.

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We review the electronic structure of nickelate superconductors with and without effects of electronic correlations. As a minimal model, we identify the one-band Hubbard model for the Ni 3dx2−y2 orbital plus a pocket around the A-momentum. The latter, however, merely acts as a decoupled electron reservoir. This reservoir makes a careful translation from nominal Sr-doping to the doping of the one-band Hubbard model mandatory. Our dynamical mean-field theory calculations, in part already supported by the experiment, indicate that the Γ pocket, Nd 4f orbitals, oxygen 2p, and the other Ni 3d orbitals are not relevant in the superconducting doping regime. The physics is completely different if topotactic hydrogen is present or the oxygen reduction is incomplete. Then, a two-band physics hosted by the Ni 3dx2−y2 and 3d3z2−r2orbitals emerges. Based on our minimal modeling, we calculated the superconducting Tc vs. Sr-doping x phase diagram prior to the experiment using the dynamical vertex approximation. For such a notoriously difficult to determine quantity as Tc, the agreement with the experiment is astonishingly good. The prediction that Tc is enhanced with pressure or compressive strain has been confirmed experimentally as well. This supports that the one-band Hubbard model plus an electron reservoir is the appropriate minimal model.

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“…We note that in the data presented here, the mild tensile strain is playing only a secondary role in the determination of the thickness dependence of the crystal field and spin excitation energy. In other cases, e.g., for CaCuO 2 [26] and La 2 CuO 4 grown on different substrates [27], the larger strain leads to sizable changes of the hopping integrals that govern the 3d orbital energy splitting and the superexchange parameter J . On the contrary, here the dominant effect is the oxygen deficiency and correspondingly lower doping level of the ultrathin films, which leads to modifications of the RIXS spectra similar to those observed in bulk crystals, i.e., the broadening of the magnetic peak, with no or little variation of its energy position as a function of doping [28].…”

Section: Resultsmentioning

confidence: 99%

Structural, Electronic and Magnetic Properties of a Few Nanometer-Thick Superconducting NdBa2Cu3O7 Films

et al. 2020

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Epitaxial films of high critical temperature ( T c ) cuprate superconductors preserve their transport properties even when their thickness is reduced to a few nanometers. However, when approaching the single crystalline unit cell (u.c.) of thickness, T c decreases and eventually, superconductivity is lost. Strain originating from the mismatch with the substrate, electronic reconstruction at the interface and alteration of the chemical composition and of doping can be the cause of such changes. Here, we use resonant inelastic x-ray scattering at the Cu L 3 edge to study the crystal field and spin excitations of NdBa 2 Cu 3 O 7 − x ultrathin films grown on SrTiO 3 , comparing 1, 2 and 80 u.c.-thick samples. We find that even at extremely low thicknesses, the strength of the in-plane superexchange interaction is mostly preserved, with just a slight decrease in the 1 u.c. with respect to the 80 u.c.-thick sample. We also observe spectroscopic signatures for a decrease of the hole-doping at low thickness, consistent with the expansion of the c-axis lattice parameter and oxygen deficiency in the chains of the first unit cell, determined by high-resolution transmission microscopy and x-ray diffraction.

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Strain-engineering Mott-insulating La2CuO4

Cited by 46 publications

References 51 publications

Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄

Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄

Phase Diagram of Nickelate Superconductors Calculated by Dynamical Vertex Approximation

Structural, Electronic and Magnetic Properties of a Few Nanometer-Thick Superconducting NdBa2Cu3O7 Films

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Strain-engineering Mott-insulating La2CuO4

Cited by 46 publications

References 51 publications

Strain engineering of the charge and spin-orbital interactions in Sr 2 IrO 4

Strain engineering of the charge and spin-orbital interactions in Sr 2 IrO 4

Phase Diagram of Nickelate Superconductors Calculated by Dynamical Vertex Approximation

Structural, Electronic and Magnetic Properties of a Few Nanometer-Thick Superconducting NdBa2Cu3O7 Films

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Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄

Strain engineering of the charge and spin-orbital interactions in Sr ₂ IrO ₄