Carbon nanotube sensor for vibrating molecules

The transport properties of a CNT capacitively coupled to a molecule vibrating along one of its librational modes are studied and its transport properties analyzed in the presence of an STM tip. We evaluate the linear charge and thermal conductances of the system and its thermopower. They are dominated by position-dependent Franck-Condon factors, governed by a position-dependent effective coupling constant peaked at the molecule position. Both conductance and thermopower allow to extract some information on the position of the molecule along the CNT. Crucially, however, thermopower sheds also light on the vibrational levelspacing, allowing to obtain a more complete characterization of the molecule even in the linear regime

Membudayakan kitar semula dalam masyarakat

We study parametric quantum pumping in a two-dimensional topological insulator bar in the presence of electron interactions described by a helical Luttinger liquid. The pumping current is generated by two point contacts whose tunneling amplitudes are modulated in time. The helical nature of the edge states of the system ensures the generation of a pumped spin current that is determined by interference effects related to spin-flipping or spin-preserving tunneling at the quantum point contacts and which can be controlled by all electrical means. We show that the period of oscillation and the position of the zeros of the spin current depend on the strength of the electron interactions, giving the opportunity to directly extract information about them when measured

Wigner oscillations in strongly correlated carbon nanotube quantum dots

The competition between Friedel and Wigner oscillations in the density of strongly interacting carbon nanotubes is inspected within the Luttinger liquid picture. The power laws of the low temperature density oscillations are different from the usual case of quantum dots defined in quantum wires. Temperature plays an important role in the visibility of Wigner oscillations: both Friedel and Wigner oscillations are suppressed, but Friedel oscillations are suppressed at much lower temperature, signalling the incipience of spin-incoherent Luttinger liquid state

Fractional charge oscillations in quantum dots with quantum spin Hall effect

We show that correlated two-particle backscattering can induce fractional charge oscillations in a quantum dot built at the edge of a two-dimensional topological insulator by means of magnetic barriers. The result nicely complements recent works where those fractional oscillations were predicted in the strong-coupling regime. Moreover, since by rotating the magnetization of the barriers a fractional charge can be trapped in the dot via the Jackiw-Rebbi mechanism, the system we analyze offers the opportunity to study the interplay between this noninteracting charge fractionalization and the fractionalization due to two-particle backscattering. We demonstrate that the number of fractional oscillations of the charge density depends on the magnetization angle. In fact, a rotating magnetization can add or subtract fractional charges from the dot continuously. Finally, we address the renormalization induced by two-particle backscattering on the spin density, which is characterized by a dominant oscillation with a length twice as large as the charge-density oscillations

Charge and energy fractionalization mechanism in one-dimensional channels

We study the problem of injecting single electrons into interacting one-dimensional quantum systems, a fundamental building block for electron quantum optics. It is well known that such injection leads to charge and energy fractionalization. We elucidate this concept by calculating the nonequilibrium electron distribution function in the momentum and energy domains after the injection of an energy-resolved electron. Our results shed light on how fractionalization occurs via the creation of particle-hole pairs by the injected electron. In particular, we focus on systems with a pair of counterpropagating channels, and we fully analyze the properties of each chiral fractional excitation which is created by the injection. We suggest possible routes to access their energy and momentum distribution functions in topological quantum Hall or quantum spin-Hall edge states

Current enhancement through a time-dependent constriction in fractional topological insulators

We analyze the backscattering current induced by a time-dependent constriction as a tool to probe fractional topological insulators. We demonstrate an enhancement of the total current for a fractional topological insulator induced by the dominant tunneling excitation, contrary to the decrease present in the integer case for not too strong interactions. This feature allows us to unambiguously identify fractional quasiparticles. Furthermore, the dominant tunneling processes, which may involve one or two quasiparticles depending on the interactions, can be clearly determined