111 research outputs found
Coulomb blockade at a tunnel junction between two quantum wires with long-range interaction
The non-linear current-voltage characteristic of a tunnel junction between
two Luttinger systems is calculated for an interaction with finite range.
Coulomb blockade features are found. The dissipative resistance, the
capacitance and the external impedance, which were introduced ad hoc in earlier
theories, are obtained in terms of the electron-electron interaction. The
frequency dependence of the impedance is given by the excitation spectrum of
the electrons.Comment: 5 pages, RevTeX, 2 figures, to be published in Solid State
Communication
Magnetic AC control of the spin textures in a helical Luttinger liquid
We demonstrate the possibility to induce and control peculiar spin textures
in a helical Luttinger liquid, by means of a time-dependent magnetic scatterer.
The presence of a perturbation that breaks the time-reversal symmetry opens a
gap in the spectrum, inducing single-particle backscattering and a peculiar
spin response. We show that in the weak backscattering regime asymmetric spin
textures emerge at the left and right side of the scatterer, whose spatial
oscillations are controlled by the ratio between the magnetization frequency
and the Fermi energy and by the electron interaction. This peculiar spin
response marks a strong difference between helical and non-helical liquids,
which are expected to produce symmetric spin textures even in the AC regime.Comment: 7 pages, 4 figure
On ground states of interacting Composite Fermions with spin at half filling
The effects of interactions in a 2D electron system in a strong magnetic
field of two degenerate Landau levels with opposite spins and at filling
factors 1/2 are studied. Using the Chern-Simons gauge transformation, the
system is mapped to Composite Fermions. The fluctuations of the gauge field
induce an effective interaction between the Composite Fermions which can be
attractive in both the particle-particle and in the particle-hole channel. As a
consequence, a spin-singlet (s-wave) ground state of Composite Fermions can
exist with a finite pair-breaking energy gap for particle-particle or
particle-hole pairs. The competition between these two possible ground states
is discussed. For long-range Coulomb interaction the particle-particle state is
favored if the interaction strength is small. With increasing interaction
strength there is a crossover towards the particle-hole state. If the
interaction is short range, only the particle-particle state is possible.Comment: REVTEX; 12 pages, 5 figures; submitted to Phisical Review
Parity dependent Josephson current through a helical Luttinger liquid
We consider a superconductor-two dimensional topological insulator-
superconductor junction (S-2DTI-S) and study how the 2{\pi}- and
4{\pi}-periodic Josephson currents are affected by the electron-electron
interaction. In the long-junction limit the supercurrent can by evaluated by
modeling the system as a helical Luttinger liquid coupled to superconducting
reservoirs. After having introduced bosonization in the presence of the parity
constraint we turn to consider the limit of perfect and poor interfaces. For
transparent interfaces, where perfect Andreev reflections occur at the
boundaries, the Josephson current is marginally affected by the interaction. On
the contrary, if strong magnetic scatterers are present in the weak link, the
situation changes dramatically. Here Coulomb interaction plays a crucial role
both in low and high temperature regimes. Furthermore, a phase-shift of
Josephson current can be induced by changing the direction of the magnetization
of the impurity
Local fields in nonlinear quantum transport
We investigate the dynamical interplay between currents and electromagnetic
fields in frequency-dependent transport through a single-channel quantum wire
with an impurity potential in the presence of electron-electron interactions.
We introduce and discuss a formalism which allows a self-consistent treatment
of currents and electromagnetic fields.Comment: 4 page
Generating and controlling spin-polarized currents induced by a quantum spin Hall antidot
We study an electrically controlled quantum spin Hall antidot embedded in a
two-dimensional topological insulating bar. Helical edge states around the
antidot and along the edges of the bar are tunnel coupled. The close connection
between spin and chirality, typical of helical systems, allows to generate a
spin-polarized current flowing across the bar. This current is studied as a
function of the external voltages, by varying the asymmetry between the
barriers. For asymmetric setups, a switching behavior of the spin current is
observed as the bias is increased, both in the absence and in the presence of
electron interactions. This device allows to generate and control the
spin-polarized current by simple electrical means.Comment: 7 pages, 6 figure
Transient dynamics of spin-polarized injection in helical Luttinger liquids
We analyze the time evolution of spin-polarized electron wave packets
injected into the edge states of a two-dimensional topological insulator. In
the presence of electron interactions, the system is described as a helical
Luttinger liquid and injected electrons fractionalize. However, because of the
presence of metallic detectors, no evidences of fractionalization are encoded
in dc measurements, and in this regime the system do not show deviations from
its non-interacting behavior. Nevertheless, we show that the helical Luttinger
liquid nature emerges in the transient dynamics, where signatures of
charge/spin fractionalization can be clearly identified.Comment: Contribution for the special issue of Physica E in memory of Markus
B\"uttiker. 4 figure
Energy exchange in driven open quantum systems at strong coupling
The time-dependent energy transfer in a driven quantum system strongly
coupled to a heat bath is studied within an influence functional approach.
Exact formal expressions for the statistics of energy dissipation into the
different channels are derived. The general method is applied to the driven
dissipative two-state system. It is shown that the energy flows obey a balance
relation, and that, for strong coupling, the interaction may constitute the
major dissipative channel. Results in analytic form are presented for a
particular value of strong Ohmic dissipation. The energy flows show interesting
behaviors including driving-induced coherences and quantum stochastic
resonances.Comment: 7 pages, 2 figure
Transport of fractional Hall quasiparticles through an antidot
Current statistics of an antidot in the fractional quantum Hall regime is
studied for Laughlin's series. The chiral Luttinger liquid picture of edge
states with a renormalized interaction exponent is adopted. Several
peculiar features are found in the sequential tunneling regime. On one side,
current displays negative differential conductance and double-peak structures
when . On the other side, universal sub-poissonian transport regimes are
identified through an analysis of higher current moments. A comparison between
Fano factor and skewness is proposed in order to clearly distinguish the charge
of the carriers, regardless of possible non-universal interaction
renormalizations. Super-poissonian statistics is obtained in the shot limit for
, and plasmonic effects due to the finite-size antidot are tracked.Comment: accepted for publication in Phys. Rev. B, references adde
Time-resolved pure spin fractionalization and spin-charge separation in helical Luttinger liquid based devices
Helical Luttinger liquids, appearing at the edge of two-dimensional
topological insulators, represent a new paradigm of one-dimensional systems,
where peculiar quantum phenomena can be investigated. Motivated by recent
experiments on charge fractionalization, we propose a setup based on helical
Luttinger liquids that allows to time-resolve, in addition to charge
fractionalization, also spin-charge separation and pure spin fractionalization.
This is due to the combined presence of spin-momentum locking and interactions.
We show that electric time-resolved measurements can reveal both charge and
spin properties, avoiding the need of magnetic materials. Although challenging,
the proposed setup could be achieved with nowadays technologies, promoting
helical liquids as interesting playgrounds to explore the effects of
interactions in one dimension.Comment: main text + supplementary materia
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