We suggest, and demonstrate, a systematic approach to the study of cuprate superconductors, namely, progressive change of ion size in order to systematically alter the interaction strength and other key parameters. R(Ba,Sr)2Cu3Oy (R={La, . . . Lu,Y}) is such a system where potentially obscuring structural changes are minimal. We thereby systematically alter both dielectric and magnetic properties. Dielectric fluctuation is characterized by ionic polarizability while magnetic fluctuation is characterized by exchange interactions measurable by Raman scattering. The range of transition temperatures is 70 to 107 K and we find that these correlate only with the dielectric properties, a behavior which persists with external pressure. The ultimate significance may remain to be proven but it highlights the role of dielectric screening in the cuprates and adds support to a previously proposed novel pairing mechanism involving exchange of quantized waves of electronic polarization.The physical mechanism for electron pairing in cuprate superconductors remains uncertain. While there may be a broad consensus that it is probably magnetic in origin [1] a continuing challenge was the apparent low spectral weight of associated spin fluctuations, as measured by inelastic neutron scattering [2]. Recent studies using resonant inelastic x-ray scattering (RIXS) seem to locate the missing weight by identifying intense paramagnon excitations across the entire superconducting phase diagram [3]. However, there are major material-dependent variations in superconducting properties, as summarized in Fig. 1 (see also [4]), that remain unexplained and any successful theory must account for these. The basic Hubbard model can account for the observed generic phase behavior as a function of interaction strength and doping [5] but not for these material-dependent systematics. The problem is exacerbated by the complex and variable structure of the cuprates where some of the behavior may be systematic while some may be attributable to disorder [6], or uncontrolled structural variation in terms of e.g. buckling angles and apical oxygen bond lengths.We propose an approach to resolving this impasse by developing a suite of experiments that explore the effects of external pressure and changing ion size (internal pressure) on all the key energy scales using a model system in which structural variables remain essentially unchanged. In this way the true underlying material-dependent variation might be exposed and at the same time be used to test competing theoretical models. At the very least this offers a way to systematically vary the interaction strength, a probe which has hitherto been missing in experimental studies. We illustrate the approach in the model system R(Ba,Sr) 2 Cu 3 O y by studying the system- atic variation in the nearest-neighbor exchange interaction J, as measurable by Raman two-magnon scattering under changing external and internal pressure. In R(Ba,Sr) 2 Cu 3 O y the change in buckling angle is less than 2 • for a given doping [8, ...

This work presents the successful noncovalent attachment of ∼5 nm diameter cadmium-sulfur-selenium (CdSSe) quantum dots on strips of anatase TiO 2 nanobelts. The TiO 2 nanobelts were hydrothermally synthesized from a strong alkaline solution and subsequently heat-treated to achieve the anatase phase. The self-assembledmonolayer (SAM) technique was employed to attach the quantum dots onto the nanobelts. Due to the hydrophobic nature of the quantum dots, the surface of the nanobelts was first self-assembled with a layer of hydrophobic organic layer before both mixtures were added together. The resulting nanostructure assembly and composition was confirmed via transmission-electron-microscopy (TEM) imaging, Raman spectroscopy, UV-visible absorption spectroscopy (UV-vis), and X-ray photoelectron spectroscopy (XPS). Both Raman and UV-vis spectroscopies indicate evidence of interactions between the quantum dots and nanobelts. The visible-light sensitizing effect of the quantum dots was demonstrated in photocurrent experiments.

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