An electronic current driven through a conductor can induce a current in another conductor through the famous Coulomb drag effect. Similar phenomena have been reported at the interface between a moving fluid and a conductor, but their interpretation has remained elusive. Here, we develop a quantum-mechanical theory of the intertwined fluid and electronic flows, taking advantage of the non-equilibrium Keldysh framework. We predict that a globally neutral liquid can generate an electronic current in the solid wall along which it flows. This hydrodynamic Coulomb drag originates from both the Coulomb interactions between the liquid's charge fluctuations and the solid's charge carriers, and the liquid-electron interaction mediated by the solid's phonons. We derive explicitly the Coulomb drag current in terms of the solid's electronic and phononic properties, as well as the liquid's dielectric response, a result which quantitatively agrees with recent experiments at the liquid-graphene interface. Furthermore, we show that the current generation counteracts momentum transfer from the liquid to the solid, leading to a reduction of the hydrodynamic friction coefficient through a quantum feedback mechanism. Our results provide a roadmap for controlling nanoscale liquid flows at the quantum level, and suggest strategies for designing materials with low hydrodynamic friction.
The tribology of a bubble rubbing on a solid surface is studied via interferometry. A unique experimental setup is designed for monitoring the thickness profiles of a wetting film, intercalated between the bubble and hydrophilic glass moving with speed up to 412 um/s. The determination of the 3D film thickness profiles allows us to calculate 3D maps over the wetted surface of the local capillary, disjoining and lift pressures, viscous stress and friction force. In this way the average friction force and the corresponding friction coefficient are obtained. A theoretical model for the dependence…
Fluctuation-induced ionic friction at solid-electrolyte interfaces
Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université Paris Cité（巴黎高等师范学院物理实验室）；Hamburg University of Technology, TUHH（汉堡工业大学）；Institute of Science and Technology Austria (ISTA)（奥地利科学与技术研究所）；École Polytechnique Fédérale de Lausanne (EPFL)（洛桑联邦理工学院）
We study the frictional drag force in low-dimensional systems (2D-electron and 2D-liquid systems) mediated by a fluctuating electromagnetic field which originate from Brownian motion of ions in liquid. The analysis is focused on the [2D-system-2D-system], [2D-system-semi-infinite liquid], and [2D-system-infinite liquid] configurations. We show that for 2D-electron systems the friction drag depends linearly on the relative velocity of the free carries of charge in the different media, but for 2D-liquid systems the frictional drag depends nonlinear on the relative velocity. For 2D-systems the fr…
Ti$_3$C$_2$T$_X$ nano-sheets (MXenes) are an emerging class of two-dimensional materials with outstanding potential to be employed in energy storage, catalysis, and triboelectric applications, on length scales ranging from the nano- to macroscopic. Despite rapidly accelerating interest in this new class of materials, their nanoscale frictional properties and in particular, their potential for solid lubrication on the nanoscale, have not been explored in detail yet. In this short communication, we present the first results on the nanoscale frictional characteristics of MXenes, in the form of a …
Solids at incommensurate contact display low-friction, 'superlubric', sliding. For graphene flakes on a graphite surface, superlubric sliding is only temporary due to rotation of the flakes from incommensurate to commensurate contact with the substrate. We examine this rotational channel of friction in a prototype geometry of meso- and macroscopic solid lubrication. By molecular dynamics simulations and theoretical arguments we find that two surfaces lubricated by mobile, rotating graphene flakes exhibit stable superlubric sliding as for ideally incommensurate contacts also when they are cover…
A deterministic theory describing the behavior of an ultrathin lubricant film between two atomically-smooth solid surfaces is proposed. For the description of lubricant state the parameter of excess volume arising due to chaotization of solid medium structure in the course of melting is introduced. Thermodynamic and shear melting is described consistently. Dependences of friction force on temperature of lubricant, shear velocity of rubbing surfaces, and pressure upon surfaces are analyzed. Within the framework of a simple tribological model the stick-slip mode of friction, when the lubricant p…
Exciton-mediated optical control of liquid-solid friction
MIPT（莫斯科物理技术学院）；Russian Quantum Center, Skolkovo（俄罗斯量子中心）；Westlake University（西湖大学）；St. Petersburg State University（圣彼得堡国立大学）；Institute of Science and Technology Austria (ISTA)（奥地利科学技术研究所）
Friction is one of the main sources of dissipation at liquid water/solid interfaces. Despite recent progress, a detailed understanding of water/solid friction in connection with the structure and energetics of the solid surface is lacking. Here we show for the first time that \textit{ab initio} molecular dynamics can be used to unravel the connection between the structure of nanoscale water and friction for liquid water in contact with graphene and with hexagonal boron nitride. We find that whilst the interface presents a very similar structure between the two sheets, the friction coefficient …
A deterministic theory describing the melting of an ultrathin lubricant film between two atomically smooth solid surfaces has been developed. The lubricant state is described by introducing a parameter of excess volume that arises owing to the solid structure chaotization at its melting. The thermodynamic and shear kinds of melting are described consistently. The dependences of the stationary friction force on the lubricant temperature and the shear velocity of rubbing surfaces that move with respect to each other with a constant velocity have been analyzed. In the framework of a simple tribol…
According to Stokes' law, a moving solid surface experiences dissipation that is linearly related to its velocity and the viscosity of the medium. This linear dependence on viscosity forms the basis for many characterization techniques for liquids. Unlike viscosities of different liquids, viscosities of gases vary only in a narrow range which limits their use as an effective characterization parameter using moving structures. Here we report experimental results of dissipation showing exponential dependence on viscosity for oscillating surfaces modified with nanostructures. The surface nanostru…
Compared to nanoscale friction of translational motion, the mechanisms of rotational friction have received less attention. Such motion becomes an important issue for the miniaturization of mechanical machineries which often involve rotating gears. In this study, molecular dynamics simulations are performed to explore rotational friction for solid-state gears rotating on top of different substrates. In each case, viscous damping of the rotational motion is observed and found to be induced by the pure van-der-Waals interaction between gear and substrate. The influence of different gear sizes an…
Thermal transport through liquid-solid interfaces plays an important role in many chemical and biological processes, and better understanding of liquid-solid energy transfer is expected to enable improving the efficiency of thermally driven applications. We determine the spectral distribution of thermal current at liquid-solid interfaces from nonequilibrium molecular dynamics, delivering a detailed picture of the contributions of different vibrational modes to liquid-solid energy transfer. Our results show that surface modes located at the Brillouin zone edge and polarized along the liquid-sol…
The freezing and melting of $^{4}$He in various aerogels with porosities ranging from 92 to 97% was studied using longitudinal ultrasound. The freezing pressure, detected by a change in velocity and attenuation, was elevated from that of bulk by about 0.3 MPa, and showed little dependence on aerogel porosity. We report measurements of the transmission of sound through the solid-liquid interface in aerogel, for the first time, which was independent of temperature and unaffected by a small addition of $^3$He, unlike the bulk interface. This indicates that crystal growth was suppressed by disorde…
We study the edge--states excitations of a droplet of quantum Hall liquid embedded in an electron (Wigner) solid. The presence of strong correlations between the liquid and solid sectors in the ground state is shown to be reflected in the density of states $D(E)$, associated with the excitations of the liquid--solid interface. We find that the prominent effect of these correlations is a suppression of $D(E)$ with respect to its value ($D_0(E)$) in the absence of the Wigner solid environment: $D(E) \sim e^{-α|E|}D_0(E)$. The coefficient $α$ (which is shown to vanish for a perfectly regular dist…
