初中物理实验器材替代及实验改进点滴

现行的初中物理教材中已编入了大量的实验,有演示实验,有学生分组实验,有课后小实验、小制作等,从我们这几年的教学实践中对该教材的使用来看,其中还存在许多不足,例如,有些实验因为自身设计、器材或实际教学条件的局限,效果还不够理想;据我们多年实践,做了如下一些改进,效果良好,     

Growth of high-quality perovskite (110)-SrIrO_3 thin films using reactive molecular beam epitaxy

Recently, 5d transition metal iridates have been reported as promising materials for the manufacture of exotic quantum states. Apart from the semimetallic ground states that have been observed, perovskite SrIrO_3 is also predicted to have a lattice-symmetrically protected topological state in the(110) plane due to its strong spin–orbit coupling and electron correlation. Compared with non-polar(001)-SrIrO_3, the especial polarity of(110)-SrIrO_3 undoubtedly adds the difficulty of fabrication and largely impedes the research on its surface states. Here, we have successfully synthesized high-quality(110)-SrIrO_3 thin films on(110)-SrTiO_3 substrates by reactive molecular beam epitaxy for the first time. Both reflection high-energy electron diffraction patterns and x-ray diffraction measurements suggest the expected orientation and outstanding crystallinity. A(1 × 2) surface reconstruction driven from the surface instability, the same as that reported in(110)-SrTiO_3, is observed. The electric transport measurements uncover that(110)-SrIrO_3 exhibits a more prominent semimetallic property in comparison to(001)-SrIrO_3.     

Two Gaps in Semiconducting EuSbTe_3 Studied by Angle-Resolved Photoemission Spectroscopy

Using angle-resolved photoemission spectroscopy, we study the low-energy electronic structure of a layered ternary telluride EuSbTe_3 semiconductor. It is found that the photoemission constant energy contours can be well described by the simple two-parameter(t_(perp) and t_(para)) tight-binding model based on the Te orbitals in square-net planes of EuSbTe_3, suggesting its Te 5p orbitals dominated low-lying electronic structure, which is reminiscent of other rare-earth tritellurides. However, a possible charge-density-wave gap of 80 meV is found to persist in 300 K,which renders the unexpected semiconducting properties in EuSbTe_3. Moreover, we reveal an extra band gap occurring around 200 meV below the Fermi level at low temperatures, which can be attributed to the interaction between the main and folded bands due to lattice scatterings. Our findings provide the first comprehensive understanding of the electronic structure of layered ternary tellurides, which lays the basis for future research on these compounds.