Metallization of Quantum Material GaTa4Se8 at High Pressure
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99 GENERAL AND MISCELLANEOUS↗
Engineering topics
Weng, H.
Publications and source records attributed to Weng, H..
Chiral terahertz wave emission from the Weyl semimetal TaAs
Weyl semimetals host chiral fermions with distinct chiralities and spin textures. Optical excitations involving those chiral fermions can induce exotic carrier responses, and in turn lead to novel optical phenomena. Here, we discover strong coherent terahertz emission from Weyl semimetal TaAs, which is demonstrated as a unique broadband source of the chiral terahertz wave. The polarization control of the THz emission is achieved by tuning photoexcitation of ultrafast photocurrents via the photogalvanic effect. In the near-infrared regime, the photon-energy dependent nonthermal current due to the predominant circular photogalvanic effect can be attributed to the radical change of the band velocities when the chiral Weyl fermions are excited during selective optical transitions between the tilted anisotropic Weyl cones and the massive bulk bands. Our findings provide a design concept for creating chiral photon sources using quantum materials and open up new opportunities for developing ultrafast opto-electronics using Weyl physics.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Decadal-Interdecadal SST Variability and Regional Climate Teleconnections
Dominant modes of decadal and interdecadal SST variability and their impacts on summertime rainfall variability over East Asia and the North America are studied. Two dominant modes of interdecadal SST variability, one associated with El Nino-like warming in the global oceans and one with an east-west seesaw variation in the equatorial Pacific have been identified. The first mode is associated in part with a long-term warming trend in the topical oceans and cooling over the northern Pacific. The second mode suggests an westward shift and strengthening of the Walker circulation from 1960s to the 1980s. Over East Asian, the first SST mode is correlated with reduced rainfall in northern China and excessive rainfall in central China. This SST mode is also associated with the tendency for increased rainfall over the midwest region, and reduced rainfall over the east Coast of the US. The results suggest a teleconnection pattern which links the occurrences of drought and floods over the Asian monsoon and the US summertime time climate. This teleconnection is likely to be associated with decadal variability of the East Asian jetstream, which are affected by strong land surface heating over the Siberian region, as well as El Nino-like SST forcings. The occurrences of major droughts and floods in the East Asian and US continent in recent decades are discussed in light of the above teleconnection patterns.
Lau, William K. M.↗