Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userOrbital-Degenerate Paramagnetic Metal Sr2MoO4: An Electronic Analogue to Sr2RuO4
58
0
0.0
(
0
)
Authors
Shin-Ichi Ikeda
Ask ChatGPT about the research
No Arabic abstract
We present the first systematic study on polycrystalline Sr2MoO4 as an electronic analogue to the spin-triplet superconductor Sr2RuO4. The Pauli paramagnetic susceptibility and metallic behaviors of specific heat and electrical resistivity have been observed. The density of states at the Fermi level D(EF) deduced from the results is about three times smaller than that of Sr2RuO4. Any indication of superconductivity intrinsic to Sr2MoO4 has not been observed down to 25 mK, which may correspond to the smaller D(EF). We discuss the origin of the difference in electronic states between Sr2MoO4 and Sr2RuO4.
rate research
Read More
At a temperature of roughly 1,K, ce{Sr2RuO4} undergoes a transition from a normal Fermi liquid to a superconducting phase. Even while the former is relatively simple and well understood, the superconducting state is not even after 25 years of study. More recently it has been found that critical temperatures can be enhanced by application of uniaxial strain, up to a critical strain, after which it falls off. In this work, we take an `instability approach and seek for divergences in susceptibilities. This provides an unbiased way to distinguish tendencies to competing ground states. We show that in the unstrained compound the singlet and triplet instabilities of the normal Fermi liquid phase are closely spaced. Under uniaxial strain electrons residing on all orbitals contributing to the Fermiology become more coherent while the electrons of Ru-$d_{xy}$ character become heavier and electrons of Ru-$d_{xz,yz}$ characters become lighter. In the process, Im,$chi(mathbf{q},omega)$ increases rapidly around the incommensurate vector $mathbf{q}{=}(0.3,0.3,0)2pi/a$ while it gets suppressed at all other commensurate vectors, in particular at $q{=}0$, which is essential for spin-triplet superconductivity. Thus the triplet superconducting instability remains the lagging instability of the system and the singlet instability enhances under strain, leading to a large energy-scale separation between these competing instabilities. At large strain an instability to a spin density wave overtakes the superconducting one. The analysis relies on a high-fidelity, emph{ab initio} description of the one-particle properties and two-particle susceptibilities, based on the Quasiparticle Self-Consistent emph{GW} approximation augmented by Dynamical Mean Field theory. This approach is described and its high fidelity confirmed by comparing to observed one- and two-particle properties.
In search of the potential realization of novel normal-state phases on the surface of Sr2RuO4 - those stemming from either topological bulk properties or the interplay between spin-orbit coupling (SO) and the broken symmetry of the surface - we revisit the electronic structure of the top-most layers by ARPES with improved data quality as well as ab-initio LDA slab calculations. We find that the current model of a single surface layer (surd2xsurd2)R45{deg} reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with LDA+SO slab calculations based on the LEED-determined surface crystal structure, reveal that (at a minimum) the sub-surface layer also undergoes a similar although weaker reconstruction. This points to a surface-to-bulk progression of the electronic states driven by structural instabilities, with no evidence for Dirac and Rashba-type states or surface magnetism.
A singular evolution toward an insulating phase, shown by 23Na and 13C NMR, has been observed in the superconducting fullerides (NH3)xNaK2C60 for x>1. Unlike most common cases, this insulating phase is non magnetic and 13C spin lattice relaxation shows the presence of a spin gap. These two features suggest that a charge disproportion from C60^(3-) to C60^(2-) and C60^(4-) can drive the system from the metallic to the insulating state. The restoring of the Na+ cation in the center of the octahedral interstice in the insulating phase, as indicated by 23Na and 2H lineshape analysis, confute the current belief that the cation off-centering is effective in quenching the superconductivity.
The electronic states near the Fermi level of recently discovered superconductor Ba$_2$CuO$_{4-delta}$ consist primarily of the Cu $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals. We investigate the electronic correlation effect and the orbital polarization of an effective two-orbital Hubbard model mimicking the low-energy physics of Ba$_2$CuO$_{4-delta}$ in the hole-rich regime by utilizing the dynamical mean-field theory with the Lanczos method as the impurity solver. We find that the hole-overdoped Ba$_2$CuO$_{4-delta}$ with $3d^8$ (Cu$^{3+}$) is in the orbital-selective Mott phase (OSMP) at half-filling, and the typical two-orbital feature remains in Ba$_2$CuO$_{4-delta}$ when the electron filling approaches $n_esim 2.5$, which closely approximates to the experimental hole doping for the emergence of the high-$T_c$ superconductivity. We also obtain that the orbital polarization is very stable in the OSMP, and the multiorbital correlation can drive orbital polarization transitions. These results indicate that in hole-overdoped Ba$_2$CuO$_{4-delta}$ the OSMP physics and orbital polarization, local magnetic moment, and spin or orbital fluctuations still exist. We propose that our present results are also applicable to Sr$_2$CuO$_{4-delta}$ and other two-orbital cuprates, demanding an unconventional multiorbital superconducting scenario in hole-overdoped high-$T_c$ cuprates.
The lattice dynamics in Sr$_2$RuO$_4$ has been studied by inelastic neutron scattering combined with shell-model calculations. The in-plane bond-stretching modes in Sr$_2$RuO$_4$ exhibit a normal dispersion in contrast to all electronically doped perovskites studied so far. Evidence for strong electron phonon coupling is found for c-polarized phonons suggesting a close connection with the anomalous c-axis charge transport in Sr$_2$RuO$_4$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
