Fermi surface, surface states, and surface reconstruction in Sr2RuO4

The electronic structure of Sr2RuO4 is investigated by high angular resolution ARPES at several incident photon energies. We address the controversial issues of the Fermi surface (FS) topology and the van Hove singularity at the M point, showing that a surface state and the replica of the primary FS due to sqrt[2]xsqrt[2] surface reconstruction are responsible for previous conflicting interpretations. The FS thus determined by ARPES is consistent with the de Haas-van Alphen results, and it provides additional information on the detailed shape of the alpha, beta, and gamma sheets.     

Pseudogap formation in the intermetallic compounds (Fe1-xVx)3Al

Optical conductivity data of the intermetallic compounds (Fe1-xVx)3Al ( 0相似文献   

Bottom-up fabrication and piezoelectric properties of CaBi<Subscript>4</Subscript>Ti<Subscript>4</Subscript>O<Subscript>15</Subscript> micro-plateaus

CaBi₄Ti₄O₁₅ (CBTi144) micro-plateaus were fabricated on Si wafers and Pt foils using a self-assembled monolayer (SAM) and a complex metal alkoxide solution. The micro-plateaus are delineated by metal masks, which are used for shadowing against the ultraviolet (UV) irradiation for decomposition of SAM to make the surface hydrophilic. The micro-plateaus crystallized to a ferroelectric phase with random orientation. The crystallization depended on the SAM-derived ultra thin layers at the surface of the substrates. The primitive PFM measurements without any top electrodes confirmed that the micro-plateaus exhibited the piezoresponse behaviors. The piezoelectric constant, d₃₃, had some distribution, and the maximum d₃₃ was confirmed as about 45 pm/V, which is identical to the d₃₃ of the polar-axis oriented CBTi144 thin films. PACS 77.84.-s; 81.20.Fw; 77.65.-j     

Raman spectroscopy of SWNTs produced by a XeCl excimer laser ablation at high temperatures

Synthesis of single-wall carbon nanotubes (SWNTs) was carried out by an ablation method using a XeCl excimer laser. It was irradiated onto a graphite target containing Co and Ni at the temperatures of 1073, 1173, 1273, 1373, 1473, 1523 and 1623 K under the atmosphere (0.1 MPa) of Ar gas with the flow rate of 12 ml/min. The measurement by a scanning/transmission electron microscope and Raman spectroscopy found the formation of SWNTs with the diameter of about 1.3 nm and the length of about 2 μm in ablated carbonaceous soot. The ratio of peak intensity of 1590 cm⁻¹ (G band) to that of 1335 cm⁻¹ (D band) in the high frequency Raman spectra increased with increasing the ambient temperature. The radial breathing mode (RBM) in the low frequency Raman spectra shows that the mean diameter of SWNTs increased with increasing the ambient temperature.     

Selective synthesis of poly(p‐oxybenzoyl) by fractional polycondensation: Enhancement of selectivity by shearing

The influence of shear flow, especially the timing for the application of shearing, was examined to enhance the selectivity for the preparation of poly(p‐oxybenzoyl) (Pp‐OB) by using hydrodynamically induced phase separation during polymerization of 4‐(4‐acetoxybenzoyloxy)benzoic acid (p‐ABAD) and m‐acetoxybenzoic acid (m‐ABA). The polymers containing few m‐oxybenzoyl (m‐OB) moieties were obtained as precipitates even at high content of m‐OB moiety in feed (χ_f) under shear flow. The content of m‐OB moiety in the precipitates (χ_p) prepared under shearing throughout the polymerization at the shear rate (γ) of 489 s^?1 was 6.3 mol % even at χ_f of 60 mol %. Especially, the Pp‐OB was obtained as the precipitates at χ_f of less than 50 mol %. The timing of the application of the shearing influenced the selectivity significantly, and the shearing just after the precipitation of the oligomers started was quite efficient to enhance the selectivity more. The χ_p of the precipitates prepared with shearing at γ of 489 s^?1 just after the precipitation was only 3.9 mol % even at χ_f of 60 mol %. The shear flow reduced the difference in the reactivity between p‐ABAD and m‐ABA, resulting in the decrease in the selectivity with regard to the formation of p‐oxybenzoyl homo‐oligomer. However, the shear flow enhanced the difference in the miscibility between homo‐oligomers and co‐oligomers. This change in the miscibility by shear flow brought about the more rapid precipitation of homo‐oligomers, leading to the enhancement of the selectivity. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Preparation of poly(p‐oxybenzoyl) crystals using direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides

Poly(p‐oxybenzoyl) (POB) crystals were prepared by reaction‐induced crystallization during direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides. Polymerizations were carried out at 300 °C in dibenzyltoluene at a concentration of 1% with three kinds of anhydrides of boronic acid such as 3,4,5‐trifluorophenylboronic acid (TFB), 4‐methoxyphenylboronic acid (MPB) and 4‐biphenylboronic acid (BPB). The POB crystals were formed as precipitates in the solution and the morphology was considerably influenced by both the structure of the boronic anhydride and its concentration (c_B). Needle‐like crystals were firmed in the presence of TFB anhydride (TFBA) at c_Bs of 5 and 10 mol % by the spiral growth of lamellae. Spherical aggregates of slab‐like crystals were formed at c_Bs from 50 to 100 mol %. The polymerization with MPB anhydride and BPB anhydride (BPBA) also yielded the needle‐like crystals at c_Bs of 50 and 5 mol %, respectively. The polymerization with TFBA at lower c_B was favorable to prepare the needle‐like crystal. Molecular weight was also influenced by the structure of the boronic anhydride and c_B. M_n increased generally with c_B and BPBA gave the highest M_n of 14.7 × 10³ at c_B of 100 mol %. The loose packing of the molecules in the crystal caused by the bulkiness of the end‐groups made the polymerization in the crystals more efficiently. Morphology and molecular weight of the POB crystals could be controlled by the chemical structure and the content of boronic anhydride. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis of thiophene/phenylene co‐oligomers. II [1]. Block and alternating co‐oligomers

We report the synthesis of block and alternating thiophene/phenylene co‐oligomers that is based either on the Suzuki coupling reaction or on the Grignard reaction. These reaction schemes enable us to obtain the target compounds at reasonably high yields. The resulting materials have been fully characterized through the solid‐state ¹³C nmr and Fourier‐transform ir as well as the ¹H nmr. Of these, the solid‐state ¹³C nmr and ir are particularly useful in characterizing the materials of higher molecular weight, since those materials are difficult to dissolve in organic solvents.