Toyota Physical and Chemical Research Institute

Various assembly manners of dodecagons composed of triangles and squares have been observed in the transmission electron microscope images of microphase-separated ternary blends of pentablock quarterpolymers of the AB1CB2D type in the bulk. N3/N4 ratios, where N3 and N4 are the numbers of triangles and squares, respectively, in the observed area, are all confirmed to be close enough to the theoretical value of 4/ ≑ 2.31 for the dodecagonal quasicrystalline state irrespective of the dodecagon assembly fashion and also of the number density of dodecagons. The appearance of the hierarchically scaled-up tiles is recognized for several types of assembly, that is, the 2 + ≑ 3.72 times and the (2 + )2 ≑ 11.37 times magnified tiles in their edge lengths are found, where the scale factor of 2 + is associated with the inflation operation. However, the areas in which the self-similarity holds are fairly narrow and limited, whereas their phason strains are reasonably small. Thus, the dodecagon assembly manners of the present sample have turned out to be far from the theoretically ideal tiling, while they rather have the feature of random tilings.

Abstract CO2 capture technology can mitigate greenhouse gas emissions and global warming. CO2 capture driven by electrochemical reactions is attractive because the operation is carried out at normal temperature and pressure and involves a simple input system using electrical energy. Although promising metal complexes with high CO2 fixation performance have been reported, there are few studies on systems that combine electrochemical reactions and metal complexes. Here, we demonstrated stable CO2 fixation‐release cycles using an electrochemical system with trinuclear Zn(II) complex (Zn3L) as the CO2 fixative and an ionic liquid as a supporting electrolyte for the stable operation. This system showed a faster CO2 fixation rate than that of an aqueous alkaline solution at the same concentration. Continuous release and refixation of CO2 were achieved by decomposition and reconstruction of the complex structure induced by H+ and OH− supplied from a bipolar membrane equipped in the electrolytic cell. The CO2 fixation‐release cycle was demonstrated even for dilute CO2 (450 ppm) in air, where the CO2 capture rate reached approximately 46 % of CO2 contained in the air under an air flow condition of 200 mL ⋅ min−1. This case, combining electrochemical drive and metal complexes, will provide a new option for CO2 capture technology.

We study hyperuniform properties for the square-triangle tilings. The tiling is generated by a local growth rule, where squares or triangles are iteratively attached to its boundary. The introduction of the probability $p$ in the growth rule, which controls the expansion of square and triangle domains, enables us to obtain various square-triangle random tilings systematically. We analyze the degree of the regularity of the point configurations, which are defined as the vertices on the square-triangle tilings, in terms of hyperuniformity. It is clarified that for $p<{p}_{c}\phantom{\rule{0.28em}{0ex}}({p}_{c}\ensuremath{\sim}0.5)$, the system can be regarded as a phase separation between square and triangular lattice domains and the variance of the point configurations obeys the scaling law ${\ensuremath{\sigma}}^{2}\ensuremath{\sim}O({R}^{2\ensuremath{-}\ensuremath{\alpha}})$ with $\ensuremath{\alpha}<0$. The configurations are antihyperuniform. On the other hand, for $p>{p}_{c}$, the squares and triangles are spatially well mixed and the point configurations belong to the hyperuniform class III with the exponent $0<\ensuremath{\alpha}<1$. This means the existence of the hyperuniform-antihyperuniform transition at $p={p}_{c}$. We also examine the structure factor of the square-triangle tilings. It is clarified that the peak structures in the large-wave-number regime are mostly common to all square-triangle tilings, while those in the small-wave-number regime strongly depend on whether the point configurations are hyperuniform or antihyperuniform.

We report on measurements of the in-plane magnetic penetration depth (λ_{ab}) in single crystals of Sr_{2}RuO_{4} down to ≃0.015 K by means of muon-spin rotation-relaxation. The linear temperature dependence of λ_{ab}^{-2} for T≲0.7 K suggests the presence of nodes in the superconducting gap. This statement is further substantiated by observation of the Volovik effect, i.e., the reduction of λ_{ab}^{-2} as a function of the applied magnetic field. The experimental zero-field and zero-temperature value of λ_{ab}=124(3) nm agrees with λ_{ab}≃130 nm, calculated based on results of electronic structure measurements reported in A. Tamai et al. [High-resolution photoemission on Sr_{2}RuO_{4} reveals correlation-enhanced effective spin-orbit coupling and dominantly local self-energies, Phys. Rev. X 9, 021048 (2019)PRXHAE2160-330810.1103/PhysRevX.9.021048]. Our analysis reveals that a simple nodal superconducting energy gap, described by the lowest possible harmonic of a gap function, does not capture the dependence of λ_{ab}^{-2} on T, so the higher angular harmonics of the energy gap function need to be introduced.

Intuitive entropic interpretations of the thermoelectric effect in metals predict an isotropic Seebeck coefficient at high temperatures in the incoherent regime even in anisotropic metals since entropy is not directional. $\mathrm{Sr}_2\mathrm{Ru}\mathrm{O}_4$ is an enigmatic material known for a well characterised anisotropic normal state and unconventional superconductivity. Recent ab-initio transport calculations of $\mathrm{Sr}_2\mathrm{Ru}\mathrm{O}_4$ that include the effect of strong electronic correlations predicted an enhanced high-temperature anisotropy of the Seebeck coefficient at temperatures above 300 K, but experimental evidence is missing. From measurements on clean $\mathrm{Sr}_2\mathrm{Ru}\mathrm{O}_4$ single crystals along both crystallographic directions, we find that the Seebeck coefficient becomes increasingly isotropic upon heating towards room temperature as generally expected. Above 300 K, however, $S$ acquires a new anisotropy which rises up to the highest temperatures measured (750 K), in qualitative agreement with calculations. This is a challenge to entropic interpretations and highlights the lack of an intuitive framework to understand the anisotropy of thermopower at high temperatures.

The reason for the absence of superconductivity in Sr2IrO4 was estimated by photoelectron spectra and photoelectron holograms. The analysis of the La photoelectron hologram concluded that La atoms are substituted to Sr sites. Two O 1s peaks were observed and were identified as the oxygens in the IrO2 and SrO planes by photoelectron holography and density functional theory (DFT) calculations. In the Ir 4f spectrum of Sr2IrO4, an unexpected Ir3+ peak was observed as much as 50% of all of the Ir. The photoelectron hologram of Ir3+ showed a displacement of about 0.15 Å. This displacement is thought to be due to the oxygen vacancies in the IrO2 plane. These oxygen vacancies and the associated local displacement of the atoms might inhibit superconductivity in spite of sufficient electron doping.

Metallic states near the Mott insulator show a variety of quantum phases including various magnetic, charge ordered states and high-temperature superconductivity in various transition metal oxides and organic solids. The emergence of a variety of phases and their competitions are likely intimately associated with quantum transitions between the electron-correlation driven Mott insulator and metals characterized by its criticality, and is related to many central questions of condensed matter. The quantum criticality is, however, not well understood when the transition is controlled by the bandwidth through physical parameters such as pressure. Here, we quantitatively estimate the universality class of the transition characterized by a comprehensive set of critical exponents by using a variational Monte Carlo method implemented as an open-source innovated quantum many-body solver, with the help of established scaling laws at a typical bandwidth-controlled Mott transition. The criticality indicates a weaker charge and density instability in contrast to the filling-controlled transition realized by carrier doping, implying a weaker instability to superconductivity as well. The present comprehensive clarification opens up a number of routes for quantitative experimental studies for complete understanding of elusive quantum Mott transition and nearby strange metal that cultivate future design of functionality.

We derive $ab$ $initio$ low-energy effective Hamiltonians (LEH) for high-temperature superconducting (SC) copper oxides Bi$_2$Sr$_2$CuO$_6$ (Bi2201, $N_{\ell}=1$, $T_c^{\rm exp} \sim 10$ K), Bi$_2$Sr$_2$CaCu$_2$O$_8$ (Bi2212, $N_{\ell}=2$, $T_c^{\rm exp} \sim 84$ K), HgBa$_2$CuO$_4$ (Hg1201, $N_{\ell}=1$, $T_c^{\rm exp} \sim 90$ K) and CaCuO$_2$ (Ca11, $N_{\ell}=\infty$, $T_c^{\rm exp} \sim 110$ K), with different experimental optimal SC transition temperature $T_c^{\rm exp}$ and number $N_{\ell}$ of laminated CuO$_2$ planes between the two neighboring block layers. We apply the latest methodology of the multiscale $ab$ $initio$ scheme for correlated electron systems (MACE), and focus on the LEH consisting of one antibonding (AB) Cu$3d_{x^2-y^2}$/O$2p_{\sigma}$ orbital centered on each Cu atom. We discuss prominent features of this LEH: (1) The ratio $U/|t_1|$ between the onsite effective Coulomb repulsion (ECR) $U$ and amplitude of nearest neighbour hopping $t_1$ increases with $T^{\rm exp}_c$ and $N_{\ell}$, consistently with the expected increase in $d$-wave SC correlation function $P_{dd}$ with $U/|t_1|$. One possible cause of the increase of $U/|t_1|$ is the replacement of apical O atoms by Cu atoms from neighbouring CuO$_2$ planes when $N_{\ell}$ increases. Furthermore, we show that the increase in distance between Cu and apical O atoms decreases the effective screening (ES) by electrons outside of the LEH and increases $U/|t_1|$. (2) For Hg1201 and Ca11, we show that $U/|t_1|$ decreases when hole doping per AB orbital $\delta$ increases, which may partly account for the disappearance of SC when $\delta$ exceeds the optimal value in experiment. (3) For $N_{\ell} \geq 2$, off-site inter-CuO$_2$ plane ECR is comparable to off-site intra-CuO$_2$ plane ECR. We discuss contributions of inter-CuO$_2$ plane ECR to both $P_{dd}$ and the stability of the SC state.