Full-range Gate-controlled Terahertz Phase Modulations with Graphene Metasurfaces

Local phase control of electromagnetic wave, the basis of a diverse set of applications such as hologram imaging, polarization and wave-front manipulation, is of fundamental importance in photonic research. However, the bulky, passive phase modulators currently available remain a hurdle for photonic integration. Here we demonstrate full-range active phase modulations in the Tera-Hertz (THz) regime, realized by gate-tuned ultra-thin reflective metasurfaces based on graphene. A one-port resonator model, backed by our full-wave simulations, reveals the underlying mechanism of our extreme phase modulations, and points to general strategies for the design of tunable photonic devices. As a particular example, we demonstrate a gate-tunable THz polarization modulator based on our graphene metasurface. Our findings pave the road towards exciting photonic applications based on active phase manipulations

Two-dimensional superconductivity at heterostructure of Mott insulating titanium sesquioxide and polar semiconductor

Heterointerfaces with symmetry breaking and strong interfacial coupling could give rise to the enormous exotic quantum phenomena. Here, we report on the experimental observation of intriguing two-dimensional superconductivity with superconducting transition temperature ($T_c$) of 3.8 K at heterostructure of Mott insulator Ti$_2$O$_3$ and polar semiconductor GaN revealed by the electrical transport and magnetization measurements. Furthermore, at the verge of superconductivity we find a wide range of temperature independent resistance associated with vanishing Hall resistance, demonstrating the emergence of quantum metallic-like state with the Bose-metal scenario of the metallic phase. By tuning the thickness of Ti$_2$O$_3$ films, the emergence of quantum metallic-like state accompanies with the appearance of superconductivity as decreasing in temperature, implying that the two-dimensional superconductivity is evolved from the quantum metallic-like state driven by the cooperative effects of the electron correlation and the interfacial coupling between Ti$_2$O$_3$ and polar GaN. These findings provide a new platform for the study of intriguing two-dimensional superconductivity with a delicate interplay of the electron correlation and the interfacial coupling at the heterostructures, and unveil the clues of the mechanism of unconventional superconductivity.Comment: 17 pages, 4 figure

Quantum metallic state in the titanium sesquioxide heterointerface superconductor

The emergence of the quantum metallic state marked by a saturating finite electrical resistance in the zero-temperature limit in a variety of two-dimensional superconductors injects a new momentum to the realm of unconventional superconductivity. Despite much research efforts over last few decades, there is not yet a general consensus on the nature of this unexpected quantum metal. Here, we report the unique quantum metallic state within the hallmark of Bose-metal characterized by the saturated resistance and simultaneously vanished Hall resistance in the titanium sesquioxide heterointerface superconductor Ti$_2$O$_3$/GaN. Strikingly, the quantum bosonic metallic state proximate to the two-dimensional superconductivity-metal transition tuned by magnetic fields persists in the normal phase, suggesting that the existence of composite bosons formed by electron Cooper pairs survives even in the normal phase. Our work marks the observation of the preformed electron Cooper pairs in heterointerface superconductor and sheds new light on understanding the underlying pairing mechanism of unconventional superconductivity.Comment: 6 pages, 4 figure

The fast light of CsI(Na) crystals

The responds of different common alkali halide crystals to alpha-rays and gamma-rays are tested in our research. It is found that only CsI(Na) crystals have significantly different waveforms between alpha and gamma scintillations, while others have not this phenomena. It is suggested that the fast light of CsI(Na) crystals arises from the recombination of free electrons with self-trapped holes of the host crystal CsI. Self-absorption limits the emission of fast light of CsI(Tl) and NaI(Tl) crystals.Comment: 5 pages, 11 figures Submit to Chinese Physics

The Intelligent Transportation System Using the Infrared Sensors Based on the ZigBee Protocol and Eclipse

There are more and more cars. The traffic jam cost people a lot of time on the road. This system got the number of the cars in waiting on every crossroad by the infrared sensors in the CC2530. Based on the Zigbee protocol, the routers embedded in the infrared sensors sent the information of cars in waiting to the coordinator wirelessly. Then the coordinator sent the information to the website which is developed on the Eclipse platform through the serial port. People can check the designated crossroad whether there is the traffic jam by smart telephone or the web browser. This system can release the newest information. It can be widely applied in the transportation system