Yang-Yang Lv

Broadband Photovoltaic Detectors Based on an Atomically Thin Heterostructure

van der Waals junctions of two-dimensional materials with an atomically sharp interface open up unprecedented opportunities to design and study functional heterostructures. Semiconducting transition metal dichalcogenides have shown tremendous potential for future applications due to their unique electronic properties and strong light-matter interaction. However, many important optoelectronic applications, such as broadband photodetection, are severely hindered by their limited spectral range and reduced light absorption. Here, we present a p-g-n heterostructure formed by sandwiching graphene with a gapless band structure and wide absorption spectrum in an atomically thin p-n junction to overcome these major limitations. We have successfully demonstrated a MoS2-graphene-WSe2 heterostructure for broadband photodetection in the visible to short-wavelength infrared range at room temperature that exhibits competitive device performance, including a specific detectivity of up to 10(11) Jones in the near-infrared region. Our results pave the way toward the implementation of atomically thin heterostructures for broadband and sensitive optoelectronic applications.

Experimental Observation of Topological Edge States at the Surface Step Edge of the Topological Insulator ZrTe 5

We report an atomic-scale characterization of ZrTe

Extremely large and significantly anisotropic magnetoresistance in ZrSiS single crystals

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Dirac line nodes and effect of spin-orbit coupling in the nonsymmorphic critical semimetals MSiS (M = Hf, Zr)

by using scanning tunneling microscopy. We observe a bulk bandgap of ~80 meV with topological edge states at the step edge, and thus demonstrate ZrTe

Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals.

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Composition and temperature-dependent phase transition in miscible Mo 1− x W x Te 2 single crystals

is a two dimensional topological insulator. It is also found that an applied magnetic field induces energetic splitting and spatial separation of the topological edge states, which can be attributed to a strong link between the topological edge states and bulk topology. The perfect surface steps and relatively large bandgap make ZrTe

Three-dimensional nature of the band structure of ZrTe5 measured by high-momentum-resolution photoemission spectroscopy [3D nature ZrTe5 band structure measured by high-momentum-resolution photoemission spectroscopy]

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Strong correlation of the growth mode and electrical properties of BiCuSeO single crystals with growth temperature

be a potential candidate for future fundamental studies and device applications.

Composition dependent phase transition and its induced hysteretic effect in the thermal conductivity of WxMo1−xTe2

Recently, the extremely large magnetoresistance (MR) observed in transition metal telluride, like WTe2, attracted much attention because of the potential applications in magnetic sensor. Here, we report the observation of extremely large magnetoresistance as 3.0 × 104% measured at 2 K and 9 T magnetic field aligned along [001]-ZrSiS. The significant magnetoresistance change (∼1.4 × 104%) can be obtained when the magnetic field is titled from [001] to [011]-ZrSiS. These abnormal magnetoresistance behaviors in ZrSiS can be understood by electron-hole compensation and the open orbital of Fermi surface. Because of these superior MR properties, ZrSiS may be used in the magnetic sensors.

Growth of Black Phosphorus Nanobelts and Microbelts

Topological Dirac semimetals (TDSs) represent a new state of quantum matter recently discovered that offers a platform for realizing many exotic physical phenomena. A TDS is characterized by the linear touching of bulk (conduction and valance) bands at discrete points in the momentum space [i.e., three-dimensional (3D) Dirac points], such as in Na3Bi and Cd3As2. More recently, new types of Dirac semimetals with robust Dirac line nodes (with nontrivial topology or near the critical point between topological phase transitions) have been proposed that extend the bulk linear touching from discrete points to one-dimensional (1D) lines. In this paper, using angle-resolved photoemission spectroscopy (ARPES), we explored the electronic structure of the nonsymmorphic crystals MSiS (M = Hf, Zr). Remarkably, by mapping out the band structure in the full 3D Brillouin zone (BZ), we observed two sets of Dirac line-nodes in parallel with the k(z) axis and their dispersions. Interestingly, along directions other than the line nodes in the 3D BZ, the bulk degeneracy is lifted by spin-orbit coupling (SOC) in both compounds with larger magnitude in HfSiS. Our paper not only experimentally confirms a new Dirac line-node semimetal family protected by nonsymmorphic symmetry but also helps understanding and further exploring the exotic properties, as well as practical applications of the MSiS family of compounds.