Due to the novel optical and optoelectronic properties, two dimensional (2D) materials have received increasing interests for optoelectronics applications. Discovering new properties and functionalities of 2D materials are challenging yet promising. Here broadband polarization sensitive photodetectors based on few layer ReS 2 are demonstrated. The transistor based on few layer ReS 2 shows an n-type behavior with the mobility of about 40 cm 2 V -1 s -1 and on/off ratio of 10 5 . The polarization dependence of photoresponse is ascribed to the unique anisotropic in-plane crystal structure, consistent with the optical absorption 2 anisotropy. The linear dichroic photodetection with a high photoresponsivity reported here demonstrates a route to exploit the intrinsic anisotropy of 2D materials and the possibility to open up new ways for the applications of 2D materials for light polarization detection.

Negative compressibility is a sign of thermodynamic instability of open [1][2][3] or non-equilibrium [4,5] systems. In quantum materials consisting of multiple mutually coupled subsystems, the compressibility of one subsystem can be negative if it is countered by positive compressibility of the others. Manifestations of this effect have so far been limited to low-dimensional dilute electron systems [6][7][8][9][10][11]. Here we present evidence from angle-resolved photoemission spectroscopy (ARPES) for negative electronic compressibility (NEC) in the quasi-three-dimensional (3D) spinorbit correlated metal (Sr 1−x La x ) 3 Ir 2 O 7 . Increased electron filling accompanies an anomalous decrease of the chemical potential, as indicated by the overall movement of the deep valence bands.Such anomaly, suggestive of NEC, is shown to be primarily driven by the lowering in energy of the conduction band as the correlated bandgap reduces. Our finding points to a distinct pathway towards an uncharted territory of NEC featuring bulk correlated metals with unique potential for applications in low-power nanoelectronics and novel metamaterials.

Periodic density functional theory calculations elucidate carbon monoxide coverage effects on platinum and ruthenium surfaces. As expected the CO stretching frequencies increase with coverage. Unexpectedly, overlap population calculations show that increased stretching frequencies may not always correspond to stronger bonds. A theoretical framework is established based on a modified π-attraction σ-repulsion scheme. This phenomenological model directly relates the internal adsorbate bond strength to the net change of the carbon 2s and 2p xy contributions to the π- and σ-components, respectively. The variation of the metal–surface bond is examined by using the charges, polarizations, and electron densities of the adsorbate CO orbitals. For the systems studied here, the traditional frontier orbital model of the 5σ-donation/2π*-back-donation with the metal substrate bands is not always sufficient to explain the relative C–O and C–Metal bonds strengths.

Periodic density functional theory calculations on carbon monoxide (CO) adsorbed atop on platinum−osmium binary alloys (PtOs 2 and PtOs 4 ) and the platinum−ruthenium−osmium tertiary alloy (PtRu 2 Os 2 ) are used to elucidate the changes in the C−O and C−Pt bonds upon alloying Pt with Ru/ Os atoms. As Pt is alloyed with Ru/Os atoms, the adsorbate internal bond (C−O bond) and the adsorbate−metal bond (C−Pt bond) strengthen following the substrate trends of PtOs 4 > Pt > PtOs 2 > PtRu 2 Os 2 and Pt > PtOs 4 > PtOs 2 > PtRu 2 Os 2 , respectively. These trends are manifested by the corresponding C−O and C−Pt stretching frequencies and the CO adsorption energy variations. Here, we establish a theoretical framework based on the π-attraction σ-repulsion mechanism to explain the above results. This model correlates the charges, polarizations, and electron densities of the adsorbate CO orbitals, and the sp/d populations of the adsorbing Pt atom. For the systems studied here, the traditional theoretical model of 5σ-donation/2π*-back-donation with the metal substrate bands is not always sufficient to explain the relative C−O and C−Pt bonds strengths.

We report on an angle resolved photoemission (ARPES) study of bulk electron-doped perovskite iridate, (Sr1−xLax)3Ir2O7. Fermi surface pockets are observed with a total electron count in keeping with that expected from La substitution. Depending on the energy and polarization of the incident photons, these pockets show up in the form of disconnected “Fermi arcs”, reminiscent of those reported recently in surface electron-doped Sr2IrO4. Our observed spectral variation is consistent with the coexistence of an electronic supermodulation with structural distortion in the system.