Janus monolayers of transition metal dichalcogenides.

Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements

A millisecond quantum memory for scalable quantum networks

Scalable quantum information processing critically depends on the capability of storage of a quantum state. In particular, a long-lived storable and retrievable quantum memory for single excitations is of crucial importance to the atomic-ensemble-based long-distance quantum communication. Although atomic memories for classical lights and continuous variables have been demonstrated with milliseconds storage time, there is no equal advance in the development of quantum memory for single excitations, where only around 10 $\mu$s storage time was achieved. Here we report our experimental investigations on extending the storage time of quantum memory for single excitations. We isolate and identify distinct mechanisms for the decoherence of spin wave (SW) in atomic ensemble quantum memories. By exploiting the magnetic field insensitive state, ``clock state", and generating a long-wavelength SW to suppress the dephasing, we succeed in extending the storage time of the quantum memory to 1 ms. Our result represents a substantial progress towards long-distance quantum communication and enables a realistic avenue for large-scale quantum information processing.Comment: 11pages, 4 figures, submitted for publicatio

Effects of paclitaxel and doxorubicin in histocultures of hepatocelular carcinomas

[[abstract]]Cancer has been the leading cause of death in Taiwan over the past two decades and liver cancer is the leading cause of all cancer deaths in Taiwan with a trend of increase in incidence. Therapeutic options and efficacy for liver cancer have been limited and the 5-year survival rate is less than 7% in the Unite States. The study was conducted to establish a histoculture system of human hepatocellular carcinomas (HCC) for biological and pharmacological studies and to determine the efficacy of anticancer drugs with the established HCC histocultures. Patient HCC tissues freshly obtained after surgeries were prepared and histocultured. The histocultured HCC were treated with doxorubicin and paclitaxel of various concentrations for 96-h. Upon drug treatments, the activity of tumor cell proliferation and extent of cell death induction were measured and changes of the alpha-fetoprotein levels in the culture medium were determined. We demonstrated that human HCC can be successfully cultured in a 3-dimensional histoculture system and used for pharmacological studies. Doxorubicin and paclitaxel showed concentration-dependent activities in anti-proliferation and cell death induction against the human HCC. Inhibitory effects of both drugs on alpha-fetoprotein production of the cultured HCC were in agreement with their anti-proliferative effects. Exposure time-dependent antitumoral effects of paclitaxel treatments at 3-, 24-, and 96-h against the histocultured HCC PLC/PRF/5 xenograft tumors were also observed. In conclusion, we have demonstrated a histoculture system for patient HCC and it can be utilized in selection of active drugs prior to treatments in patients and in evaluation of new agents against HCC, for which therapeutic agents are in desperate needs worldwide