900 research outputs found
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
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
Signatures of fractional Hall quasiparticles in moments of current through an antidot
The statistics of tunneling current in a fractional quantum Hall sample with
an antidot is studied in the chiral Luttinger liquid picture of edge states. A
comparison between Fano factor and skewness is proposed in order to clearly
distinguish the charge of the carriers in both the thermal and the shot limit.
In addition, we address effects on current moments of non-universal exponents
in single-quasiparticle propagators. Positive correlations, result of
propagators behaviour, are obtained in the shot noise limit of the Fano factor,
and possible experimental consequences are outlined
Multiple quasiparticle Hall spectroscopy investigated with a resonant detector
We investigate the finite frequency (f.f.) noise properties of edge states in
the quantum Hall regime. We consider the measurement scheme of a resonant
detector coupled to a quantum point contact in the weak-backscattering limit. A
detailed analysis of the difference between the "measured" noise, due to the
presence of the resonant detector, and the symmetrized f.f. noise is presented.
We discuss both the Laughlin and Jain sequences, studying the tunnelling
excitations in these hierarchical models. We argue that the measured noise can
better distinguish between the different excitations in the tunnelling process
with respect to the symmetrized f.f. counterpart in an experimentally relevant
range of parameters. Finally, we illustrate the effect of the detector
temperature on the sensibility of this measure.Comment: 24 pages, 8 figure
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
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
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
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