We measure the viscosity of nanometer-thick water films at the interface with an amorphous silica surface. We obtain viscosity values from three different measurements: friction force in a water meniscus formed between an oxide-terminated W tip and the silica surface under ambient conditions; similar measurements for these interfaces under water; and the repulsive "drainage" force as the two surfaces approach at various speeds in water. In all three cases, we obtain effective viscosities that are approximately 10(6) times greater than that of bulk water for nanometer-scale interfacial separations. This enhanced viscosity is not observed when we degrade the hydrophilicity of the surface by terminating it with -H or -CH3. In view of recent results from other interfaces, we conclude that the criterion for the formation of a viscous interphase is the degree of hydrophilicity of the interfacial pair.

We report the magnetoresistance (MR), Hall effect, and de Haas-van Alphen (dHvA) effect studies of single crystals of tungsten carbide, WC, which is predicted to be a new type of topological semimetal with triply degenerate nodes. With the magnetic field rotated in the plane perpendicular to the current, WC shows a field induced metal-to-insulator-like transition and large nonsaturating quadratic MR at low temperatures. As the magnetic field parallel to the current, a pronounced negative longitudinal MR only can be observed for the certain direction of current flow. Hall effect indicates WC is a perfect compensated semimetal, which may be related to the large nonsaturating quadratic MR. The analysis of dHvA oscillations reveals that WC is a multiband system with small cross-sectional areas of Fermi surface and light cyclotron effective masses. Our results indicate that WC is an ideal platform to study the recently proposed "New Fermions" with triply degenerate crossing points. The recently discovered topological semimetals (TSMs) have been studied intensively in condensed matter physics and material science due to the topologically protected band structure, which exhibits some exotic physical properties such as extremely large magnetore-sistance (MR), ultrahigh carrier mobility, anomalous Berry phase, and/or negative longitudinal MR [1-3]. Generally, TSMs can be classified into several categories according to the degeneracy and momentum space distribution of the nodal points. For example, in Dirac semimetals (DSMs) [4-9] and Weyl semimetals (WSMs) [10-13], two double-and non-degeneracy bands cross near the Fermi level (E F), which lead to the four-fold degenerate Dirac point and twofold degenerate Weyl point, respectively. In contrast to discrete points in DSMs and WSMs, two bands cross each other along a line in the Brillouin zone in nodal line semimetals [14, 15]. Besides the three kinds of TSMs mentioned above, some new types of TSMs with three-, six-, or eight-fold degenerate points near E F were proposed and these degenerate points appear at high-symmetry points in non-symmorphic space groups [16]. Based on a new mechanism , several materials with WC-type structure that belongs to symmorphic space groups, such as MoP, WC, TaN, and ZrTe et al., were then predicted to possess threefold degenerate crossing points (TPs), formed by * These authors contributed equally to this work. †

A dramatic transition in the mechanical properties of water is observed at the nanometer scale. For a water meniscus formed between two hydrophilic surfaces in the attractive region, with < or = 1 nm interfacial separation, the measured viscosity is 7 orders of magnitude greater than that of bulk water at room temperature. Grand canonical Monte Carlo simulations reveal enhancement in the tetrahedral structure and in the number of hydrogen bonds to the surfaces as a source for the high viscosity; this results from a cooperative effect of hydrogen bonding of water molecules to both hydrophilic surfaces.