Non-linear Coulomb blockade microscopy of a correlated one-dimensional quantum dot

We evaluate the chemical potential of a one-dimensional quantum dot, coupled to an atomic force microscope tip. The dot is described within the Luttinger liquid framework and the conductance peaks positions as a function of the tip location are calculated in the linear and non-linear transport regimes for an arbitrary number of particles. The differences between the chemical potential oscillations induced by Friedel and Wigner terms are carefully analyzed in the whole range of interaction strength. It is shown that Friedel oscillations, differently from the Wigner ones, are sensitive probes to detect excited spin states and collective spin density waves involved in the transport.Comment: 4 figure

Two New Species of Leafblight Fungi on Kalmia Latifolia

The evergreen shrub, Kalmia latifolia L., commonly known as mountain laurel, calico bush, or sheep-kill, grows widely on rocky, acid soils in the eastern United States. Whether growing in its natural habit or in cultivation, mountain laurel appears to be equally subject to attack by fungi. The following account characterizes and discusses two of these fungi. One of them has not been described previously and additional observations have been made regarding the developmental morphology of the other one. Both pathogens are Pyrenomycetes, one a Physalospora and the other a Diaporthe. Each produces a leafblight disease. Tiny brown discolorations on young leaves characterize the early stages of attack by both organisms. These small lesions gradually enlarge and become irregular brown spots that may encompass the major portion of the leaf surface. The invaded tissues are darkest near the margins of the lesions, but a reddish zone lies between the darker border and the surrounding green tissues. Severely attacked leaves are deformed and shed prematurely. The reproductive structures of the Physalospora occur on the lower surface and begin to develop before the leaves are shed. The pycnidial stromata of the Diaporthe elevate the epidermis and caticle, and consequently produce grayish spots on the leaf surface. Both fungi continue to develop after the leaves have fallen, and since the mycelia extend beyond the margins of the lesions, perithecia ultimately may occupy most of the leaf surface. [excerpt

Shot noise in charge and magnetization currents of a quantum ring

The shot noise in a quantum ring, connected to leads, is studied in the presence of electron interactions in the sequential tunneling regime. Two qualitatively different noise correlations with distinctly different behaviors are identified and studied in a large range of parameters. Noise in the total current is due to the discreteness of the electron charge and can become super-Poissonian as result of electron interaction. The noise in the magnetization current is comparatively insensitive to the interaction but can be greatly enhanced if population inversion of the angular states is assumed. The characteristic time scales are studied by a Monte-Carlo simulation.Comment: 5 pages, 5 color figure

Crystallization of fractional charges in a strongly interacting quasi-helical quantum dot

The ground-state electron density of a one-dimensional spin-orbit coupled quantum dot with a Zeeman term and strong electron interaction is studied at the fractional helical liquid points. We show that at fractional filling factors $\nu=(2n+1)^{-1}$ (with $n$ a non-negative integer) the density oscillates with $N_{0}/\nu$ peak. For $n\geq 1$ a number of peaks larger than the number of electrons $N_{0}$ suggests that a crystal of fractional quasi-particles with charge $\nu e$ (with $e$ the electron charge) occurs. The reported effect is amenable of verification via transport measurements in charged AFM-coupled dot

Temperature-induced emergence of Wigner correlations in a STM-probed one-dimensional quantum dot

The temperature-induced emergence of Wigner correlations over finite-size effects in a strongly interacting one-dimensional quantum dot are studied in the framework of the spin coherent Luttinger liquid. We demonstrate that, for temperatures comparable with the zero mode spin excitations, Friedel oscillations are suppressed by the thermal fluctuations of higher spin modes. On the other hand, the Wigner oscillations, sensitive to the charge mode only, are stable and become more visible. This behavior is proved to be robust both in the thermal electron density and in the linear conductance in the presence of an STM tip. This latter probe is not directly proportional to the electron density and may confirm the above phenomena with complementary and additional information

Theory of the STM detection of Wigner molecules in spin incoherent CNTs

The linear conductance of a carbon nanotube quantum dot in the Wigner molecule regime, coupled to two scanning tunnel microscope tips is inspected. Considering the high temperature regime, the nanotube quantum dot is described by means of the spin-incoherent Luttinger liquid picture. The linear conductance exhibits spatial oscillations induced by the presence of the correlated, molecular electron state. A power-law scaling of the electron density and of the conductance as a function of the interaction parameter are found. They confirm local transport as a sensitive tool to investigate the Wigner molecule. The double-tip setup allows to explore different transport regimes with different shapes of the spatial modulation, all bringing information about the Wigner molecule

AFM probe for the signatures of Wigner correlations in the conductance of a one-dimensional quantum dot

The transport properties of an interacting one-dimensional quantum dot capacitively coupled to an atomic force microscope probe are investigated. The dot is described within a Luttinger liquid framework which captures both Friedel and Wigner oscillations. In the linear regime, we demonstrate that both the conductance peak position and height oscillate as the tip is scanned along the dot. A pronounced beating pattern in the conductance maximum is observed, connected to the oscillations of the electron density. Signatures of the effects induced by a Wigner molecule are clearly identified and their stability against the strength of Coulomb interactions are analyzed. While the oscillations of the peak position due to Wigner get enhanced at strong interactions, the peak height modulations are suppressed as interactions grow. Oscillations due to Friedel, on the other hand, are robust against interaction.Comment: 9 figure

Probing Wigner correlations in a suspended carbon nanotube

The influence of the electron-vibron coupling on the transport properties of a strongly interacting quantum dot built in a suspended carbon nanotube is analyzed. The latter is probed by a charged AFM tip scanned along the axis of the CNT which induces oscillations of the chemical potential and of the linear conductance. These oscillations are due to the competition between finite-size effects and the formation of a Wigner molecule for strong interactions. Such oscillations are shown to be suppressed by the electron-vibron coupling. The suppression is more pronounced in the regime of weak Coulomb interactions, which ensures that probing Wigner correlations in such a system is in principle possible