This article reviews manipulation of single molecules by scanning tunnelling microscopes, in particular vertical manipulation, lateral manipulation, and inelastic electron tunnelling (IET) ...manipulation. For a better understanding of these processes, we shortly review imaging by scanning tunnelling microscopy – as a prerequisite to detect the manipulated species and to verify the result of the manipulation – as well as scanning tunnelling spectroscopy and IET spectroscopy which are used to chemically identify the molecules before and after the manipulation that employs the tunnelling current.
This article reviews manipulation of single molecules by scanning tunnelling microscopes, in particular vertical manipulation, lateral manipulation, and inelastic electron tunnelling manipulation. For a better understanding of these processes, the authors shortly review imaging by scanning tunnelling microscopy – as a prerequisite to detect the manipulated species and to verify the result of the manipulation – as well as scanning tunnelling spectroscopy and inelastic electron tunnelling spectroscopy which are used to chemically identify the molecules before and after the manipulation that employs the tunnelling current.
The reliability by which molecular motor proteins convert undirected energy input into directed motion or transport has inspired the design of innumerable artificial molecular motors. We have ...realized and investigated an artificial molecular motor applying scanning tunneling microscopy (STM), which consists of a single acetylene (C₂H₂) rotor anchored to a chiral atomic cluster provided by a PdGa(111) surface that acts as a stator. By breaking spatial inversion symmetry, the stator defines the unique sense of rotation. While thermally activated motion is nondirected, inelastic electron tunneling triggers rotations, where the degree of directionality depends on the magnitude of the STM bias voltage. Below 17 K and 30-mV bias voltage, a constant rotation frequency is observedwhich bears the fundamental characteristics of quantum tunneling. The concomitantly high directionality, exceeding 97%, implicates the combination of quantum and nonequilibrium processes in this regime, being the hallmark of macroscopic quantum tunneling. The acetylene on PdGa(111) motor therefore pushes molecular machines to their extreme limits, not just in terms of size, but also regarding structural precision, degree of directionality, and cross-over from classical motion to quantum tunneling. This ultrasmall motor thus opens the possibility to investigate in operando effects and origins of energy dissipation during tunneling events, and, ultimately, energy harvesting at the atomic scales.
The last decade has seen an intense renewed debate on tunnelling time, both from a theoretical and an experimental perspective. Here, we review recent developments and new insights in the field of ...strong-field tunnel ionization related to tunnelling time, and apply these findings to the interpretation of the attoclock experiment Landsman et al. Optica 2014, 1, 343. We conclude that models including finite tunnelling time are consistent with recent experimental measurements.
Abbreviations: A: adiabatic; ADK: Ammosov, Delone and Krainov model (1, 2); CEO: carrier-envelope-offset phase
; CoM: centre of mass; CTMC: classical trajectory monte carlo simulation; FWHM: full width half maximum; IR: infrared; KR: Keldysh-Rutherford model; NA: non-adiabatic; PMD: photoelectron momentum distribution; PPT: Perelomov, Popov and Terent'ev model (3, 4); SAE: single active electron approximation; SCT: singleclassical trajectory; SFA: strong field approximation; TDSE: time-dependent Schrödinger equation
Tunneling of electrons through a potential barrier is fundamental to chemical reactions, electronic transport in semiconductors and superconductors, magnetism, and devices such as terahertz ...oscillators. Whereas tunneling is typically controlled by electric fields, a completely different approach is to bind electrons into bosonic quasiparticles with a photonic component. Quasiparticles made of such light-matter microcavity polaritons have recently been demonstrated to Bose-condense into superfluids, whereas spatially separated Coulomb-bound electrons and holes possess strong dipole interactions. We use tunneling polaritons to connect these two realms, producing bosonic quasiparticles with static dipole moments. Our resulting three-state system yields dark polaritons analogous to those in atomic systems or optical waveguides, thereby offering new possibilities for electromagnetically induced transparency, room-temperature condensation, and adiabatic photon-to-electron transfer.
A material model for ferrite is presented, enabling an accurate calculation of the core losses from 100 kHz to 1000 kHz with a single set of scalar parameters over a decade of excitation current. It ...is based on the modelling of different material effects such as quantum tunnelling conduction between ferrite grains and atomic level magnetisation. The implications of the satisfying results of this approach on core loss modelling techniques at high frequencies are discussed.
An error-free wireless transmission of a 9 Gbit/s on–off keying modulated signal as well as a 4 k video signal is demonstrated using resonant tunnelling diodes as active elements in both the ...transmitter and the receiver. The employed system and the modulation scheme enabling the high data rate are discussed.
Molecular vibrations and quantum tunneling may link ligand binding to the function of pharmacological receptors. The well‐established lock‐and‐key model explains a ligand's binding and recognition by ...a receptor; however, a general mechanism by which receptors translate binding into activation, inactivation, or modulation remains elusive. The Vibration Theory of Olfaction was proposed in the 1930s to explain this subset of receptor‐mediated phenomena by correlating odorant molecular vibrations to smell, but a mechanism was lacking. In the 1990s, inelastic electron tunneling was proposed as a plausible mechanism for translating molecular vibration to odorant physiology. More recently, studies of ligands’ vibrational spectra and the use of deuterated ligand analogs have provided helpful information to study this admittedly controversial hypothesis in metabotropic receptors other than olfactory receptors. In the present work, based in part on published experiments from our laboratory using planarians as an experimental organism, I will present a rationale and possible experimental approach for extending this idea to ligand‐gated ion channels.
Planarians, cholinergic agents, the nicotinic acetylcholine receptor, and molecular vibrations associated with carbon‐hydrogen and carbon‐deuterium bonds.
Laser-induced electron tunnelling—which triggers a broad range of ultrafast phenomena such as the generation of attosecond light pulses, photoelectron diffraction and holography—has laid the ...foundation for strong-field physics and attosecond science. Using the attoclock constructed by single-colour elliptically polarized laser fields, previous experiments have measured the tunnelling rates, exit positions, exit velocities and delay times for some specific electron trajectories, which are mostly created at the field peak instant, that is, when the laser electric field and the formed potential barrier are stationary in terms of the derivative versus time. From the view of wave-particle dualism, the electron phase under a classically forbidden, tunnelling barrier has not been measured, which is at the heart of quantum tunnelling physics. Here we present a robust measurement of tunnelling dynamics including the electron sub-barrier phase and amplitude. We combine the attoclock technique with two-colour phase-of-phase (POP) spectroscopy to accurately calibrate the angular streaking relation and to probe the non-stationary tunnelling dynamics by manipulating a rapidly changing potential barrier. This POP attoclock directly links the measured phase of the two-colour relative phase with the ionization instant for the photoelectron with any final momentum on the detector, allowing us to reconstruct the imaginary tunnelling time and the accumulated phase under the barrier. The POP attoclock provides a general time-resolved approach to accessing the underlying quantum dynamics in intense light–matter interactions.Electron non-stationary tunnelling dynamics is probed by the attoclock with the two-colour phase-of-phase photoelectron spectroscopy. Contrary to the case of static tunnelling, angle-to-time mapping in attoclock is found to be not angularly uniform.
► Some insights into the mechanism of the shallow tunnelling method (STM) are given. ► Nine subway stations in Beijing using different approaches of the STM, combined with site monitoring data, are ...illustrated. ► Numerical simulation results are shown to compare various approaches of the STM.
This paper provides an in-depth illustration of the shallow tunnelling method (STM) used for tunnelling in shallowly buried soft ground. Limited arching effect and limited ground strength mobilization are the two mechanical characteristics of the STM. The stability of the cutting face and the dry tunnelling condition are the two preconditions that should be satisfied for the STM. Some “necessary” auxiliary methods mainly served to guarantee these two preconditions are highlighted. Five principles, namely proper auxiliary methods, sequential excavation with short advance length, rigid support with quick installation, short ring closure time and systematic deformation monitoring, which are required to follow when using the STM are summarized. The state-of-art of the STM is classified into five different construction approaches according to tunnelling sequences, which are adopted in the construction of the nine subway stations in Beijing. The tunnelling procedures, support measures and settlement characteristics associated with excavation are demonstrated. Statistical analyses of the settlement data of 342 ground surface monitoring points above these nine stations are performed to illustrate the ground deformation characteristics of the STM. Numerical simulations are also employed to study the ground deformation characteristics of different construction approaches under the same geological conditions. This paper systematically demonstrates the applicability of STM in theory and practice. It is helpful in updating the database of the world tunnel projects and serving as a practical reference for future similar projects.
PDF
