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Monolayer FeSe grown on SrTiO$_3$ (FeSe/STO) is an interfacial high temperature superconductor distinctively different from bulk FeSe. Due to the fragility of this two-dimensional system in the atmosphere, the investigation of its intrinsic superconductivity and intertwined orders has largely been limited to surface-sensitive charge probes compatible with ultra-high vacuum environment. However, the superconducting phase coherence of the interface is challenging to probe. Here, we perform in-situ mutual inductance in ultra-high vacuum on FeSe/STO in combination with band mapping by angle-resolved photoemission spectroscopy (ARPES). We find that even though the monolayer showed a gap-closing temperature above 50 K, surprisingly no diamagnetism is visible down to 5 K. This is the case for few-layer FeSe/STO until it exceeds a critical number of 5 layers where diamagnetism suddenly appears. But the superfluid density does not saturate down to the base temperature in these thick samples. On the other hand, the suppression of diamagnetism in the few-layer FeSe/STO can be lifted by depositing a FeTe layer on top. The superconducting transition is much sharper than that in the thick FeSe/STO. However, Tc and superfluid density both decrease with increasing FeTe thickness. Shining ultraviolet light on the FeTe/FeSe/STO heterostructure enhances Tc similarly independent of the FeSe thickness, showing that the diamagnetism originates at the FeSe/STO interface. Our observation may be understood by a scenario in which interfacial superconducting phase coherence is highly anisotropic.

Vortices are topological defects of type-II superconductors in an external magnetic field. In a similar fashion to a quantum anomalous Hall insulator, quantum anomalous vortex (QAV) spontaneously nucleates due to orbital-and-spin exchange interaction between vortex core states and magnetic impurity moment, breaking time-reversal symmetry (TRS) of the vortex without an external field. Here, we used scanning superconducting quantum interference device microscopy (sSQUID) to search for its signatures in iron-chalcogenide superconductor Fe(Se,Te). Under zero magnetic field, we found a stochastic distribution of isolated anomalous vortices and antivortices with flux quanta $\Phi_0$. By applying a small local magnetic field under the coil of the nano-SQUID device, we observed hysteretic flipping of the vortices reminiscent of the switching of ferromagnetic domains, suggesting locally broken-TRS. We further showed vectorial rotation of a flux line linking a paired vortex-antivortex with the local field. These unique properties of the anomalous vortices satisfied the defining criteria of QAV. Our observation suggests a quantum vortex phase with spontaneous broken-TRS in a high-temperature superconductor.

Monolayers of a prototypical cuprate high transition-temperature ($T_C$) superconductor $Bi_2Sr_2CaCu_2O_{8+\delta}$ (Bi2212) was recently found to show $T_C$ and other electronic properties similar to those of the bulk. The robustness of superconductivity in an ideal two-dimensional (2D) system was an intriguing fact that defied the Mermin-Wagner theorem. Here, we took advantage of the high sensitivity of scanning SQUID susceptometry to image the phase stiffness throughout the phase transition of Bi2212 in the 2D limit. We found susceptibility oscillated with flux between diamagnetism and paramagnetism in a Fraunhofer-like pattern up till $T_C$. The temperature and sample size-dependence of the modulation period agreed well with our Coulomb gas analogy of a finite 2D system based on Berezinskii-Kosterlitz-Thouless (BKT) transition. In the multilayers, the susceptibility oscillation differed in a small temperature regime below $T_C$ in consistent with a dimensional-crossover led by interlayer coupling. Serving as strong evidence of BKT transition in the bulk, there appeared a sharp superfluid density jump at zero-field and paramagnetism at small fields just below $T_C$. These results unified the phase transitions from the monolayer Bi2212 to the bulk as BKT transition with finite interlayer coupling. This elucidating picture favored the pre-formed pairs scenario for the underdoped cuprates regardless of lattice dimensionality.

FeTe, a non-superconducting parent compound in the iron-chalcogenide family, becomes superconducting after annealing in oxygen. Under the presence of magnetism, spin-orbit coupling, inhomogeneity and lattice distortion, the nature of its superconductivity is not well understood. Here, we combined mutual inductance technique with magneto transport to study the magnetization and superconductivity of FeTe thin films. We found that the films with the highest Tc showed non-saturating superfluid density and a strong magnetic hysteresis distinct from that in a homogeneous superconductor. Such hysteresis can be well explained by a two-level critical state model and suggested the importance of granularity to superconductivity in this compound.

In this manuscript we present a computational study on the photoluminescence properties of several heteroleptic [Ru(H)(CO)(N^N)(tpp)2]+ complexes (tpp = triphenylphosphine). A special focus is set on disentangling the temperature-dependent emissive properties. Experimentally, when cooling a solution of [Ru(H)(CO)(dmphen)(tpp)2]+ (dmphen = 5,6-dimethyl-1,10-phenanthroline) from room to cryogenic temperature, a partial emission switch from metal-to-ligand charge transfer (3MLCT) to ligand-centered (3LC) phosphorescence is observed, resulting in dual photoluminescence. Two different origins of the anomalous emissions are possible, i.e., thermal equilibration between electronically excited states or different excited state solvent relaxation effects. Our calculations are in favor of the thermally equilibrated scenario. This computational investigation highlights the importance of controlling the temperature-dependent emissive behavior for optoelectronic applications.

Ruthenium thin films can serve as protective caps for multi-layer extreme ultraviolet mirrors exposed to atomic hydrogen. Hydrogen permeation through ruthenium is problematic as it leads to blisters on the mirrors. H has been shown to exhibit low solubility in bulk Ru, and rapidly diffuses in and out of Ru. Therefore, the underlying mechanisms of the blistering effect remains unknown. This work makes use of reactive molecular dynamics simulations to study the influence of imperfections in a Ru film on the behaviour of H. For the Ru/H system, a ReaxFF force field was parametrised which reproduces structures and energies obtained from quantum-mechanical calculations. Molecular dynamics simulations have been performed with the newly-developed force field, to study the effect of tilt and twist grain boundaries on the overall diffusion behaviour of H in Ru. Our simulations show the tilt and twist grain boundaries provide energetically favourable sites for hydrogen atoms and act as sinks and highways for H. They therefore block H transport across their planes, and favour diffusion along their planes. This results in the accumulation of hydrogen at the grain boundaries. The strong effect of the grain boundaries on the hydrogen diffusion suggests tailoring the morphology of ruthenium thin films as a means to curb the rate of hydrogen permeation.

Chapter 8 of the book "Command in NATO After the Cold War: Alliance, National, & Multinational Consideration" is presented. It explores the necessary steps that Italy should take to modernize its command and operational control structures and organizations. The main factor for bringing the reforms is the influence of consolidated conservative lobbies inside the government. It explains the inability of Italian political observers to establish a strong government to bring major reforms.

Discusses the political and economic outlook of Malaysia for 2002-2003. Threat to the political stability of the country; Prices of commodities; Economic policy; Economic forecasting.

Provides an outlook for the economy of Taiwan for 2003. Domestic politics; International relations; Policy trends; Economic policy; Gross domestic product by expenditure.

Describes the economic policy of Turkey as of July 2002. Impact of the International Monetary Fund's approval of credit for the country's economic reform program on the economic status of the nation; Factors that contribute to the improving economic condition of the country.

Discusses the political and economic outlook of Singapore for 2002-2003. Leadership of prime minister Goh Chok Tong; Foreign relations with Malaysia; Fiscal and monetary policy; Economic forecasting.

Reports on developments in the economic situation of China, as of June 2002. Growth in the gross domestic product of the country in the first quarter of 2002; Participation of China in the general data dissemination system of the International Monetary Fund; Growth in exports and investments; Increase in private consumption; Decrease in consumer prices; Growth in industrial output.

Discusses the political and economic outlook of Hungary for 2002-2003. Outcome of the election held in April 2002; Foreign policy; Fiscal and monetary policy; Economic forecasting.

Discusses the domestic economy of Brazil for 2002-2003. Growth of gross domestic product; Employment; Wages; Inflation.

Forecasts the economic condition of Brazil for 2002-2003. Gross domestic product; Foreign exchange rates; Inflation; Exports and imports.

Forecasts the politics, government and economy of Hong Kong, China, from 2002 to 2003. Coalition of major political parties; Reluctance to take major revenue-boosting or expenditure-capping measures; Increase in exports of goods and services. INSET: Hong Kong at a glance: 2002-03.