Seebeck Coefficient of a Single van der Waals Junction in Twisted Bilayer Graphene

When two planar atomic membranes are placed within the van der Waals distance, the charge and heat transport across the interface are coupled by the rules of momentum conservation and structural commensurability, leading to outstanding thermoelectric properties. Here we show that an effective "interlayer phonon drag" determines the Seebeck coefficient (S) across the van der Waals gap formed in twisted bilayer graphene (tBLG). The cross-plane thermovoltage, which is non-monotonic in both temperature and density, is generated through scattering of electrons by the out-of-plane layer breathing (ZO'/ZA2) phonon modes and differs dramatically from the expected Landauer-Buttiker formalism in conventional tunnel junctions. The tunability of the cross-plane Seebeck effect in van der Waals junctions may be valuable in creating a new genre of versatile thermoelectric systems with layered solids.Comment: This document is the unedited Author's version of a submitted work that was subsequently accepted for publication in Nano Letters, copyright American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/articlesonrequest/AOR-C2EphThhD7U5a4zVMHy

Environmental variability of some edaphic components from virgin areas of tropical mangrove forest of Sundarban, India

1815-1824Level of occurrence and characteristics of some important edaphic components were studied in the intertidal surface sediments from core mangrove forest of Sundarbans in a comprehensive way for the first time. Sediments were characterized to be dominated by finer particles of silt and clay with moderate to high carbon content (0.40 - 2.76%), low cation exchange capacity (average of 11.10 me100 g-1), low available nitrogen (about 10% of total nitrogen), high salt content with alkaline nature (pH, 7.5 – 8.2) and well supply of easily available form of phosphorous (17.75 - 57.0 mg.kg-1as P2O5) and potassium (12.7-22.5 meq.100g-1). Statistical analysis revealed that clay deposition was favored at high pH (p 50%) and asymmetric distribution of organic carbon and total nitrogen with large degree of peakedness. In contrast, all other edaphic components including available nutritional elements (N, P and K) were symmetrically equilibrated by natural bio-geochemical processes into various environmental segments and thus, largely could show normal distribution. Principle component analysis (PCA) also supported the existence of complexity of the system and identified well the multitude of the most dominating factors governing the sedimentary environment in this region. Thus the entire study gives an idea about the factors controlling the biogeochemical processes of this unique ecosystem