403 research outputs found
Luttinger liquids with curvature: Density correlations and Coulomb drag effect
We consider the effect of the curvature in fermionic dispersion on the
observable properties of Luttinger liquid (LL). We use the bosonization
technique where the curvature is irrelevant perturbation, describing the decay
of LL bosons (plasmon modes). When possible, we establish the correspondence
between the bosonization and the fermionic approach. We analyze modifications
in density correlation functions due to curvature at finite temperatures, T.
The most important application of our approach is the analysis of the Coulomb
drag by small momentum transfer between two LL, which is only possible due to
curvature. Analyzing the a.c. transconductivity in the one-dimensional drag
setup, we confirm the results by Pustilnik et al. for T-dependence of drag
resistivity, R_{12} ~ T^2 at high and R_{12} ~ T^5 at low temperatures. The
bosonization allows for treating both intra- and inter-wire electron-electron
interactions in all orders, and we calculate exact prefactors in low-T drag
regime. The crossover temperature between the two regimes is T_1 ~ E_F \Delta,
with \Delta relative difference in plasmon velocities. We show that \Delta \neq
0 even for identical wires, due to lifting of degeneracy by interwire
interaction, U_{12}, leading to crossover from R_{12} ~ U_{12}^2 T^2 to R_{12}
\~ T^5/U_{12} at T ~ U_{12}.Comment: 16 pages, 10 figures, REVTE
The mean energy, strength and width of triple giant dipole resonances
We investigate the mean energy, strength and width of the triple giant dipole
resonance using sum rules.Comment: 12 page
Plasmon dispersion in quasi-one and one-dimensional systems with non-magnetic impurities
We calculate the plasmon dispersion in quasi-one-dimensional quantum wires,
in the presence of non-magnetic impurities, taking into consideration the
memory function formalism and the role of the forward scattering. The plasma
frequency is reduced by the presence of impurities. We also calculate,
analytically, the plasmon dispersion in the Born approximation, for the
scattering of the electrons by the non-magnetic impurities. We compare our
result with the numerical results of Sarma and Hwang.Comment: 12 pages, no figures, Physica E, 40, 474, (2008
RPAE versus RPA for the Tomonaga model with quadratic energy dispersion
Recently the damping of the collective charge (and spin) modes of interacting
fermions in one spatial dimension was studied. It results from the nonlinear
correction to the energy dispersion in the vicinity of the Fermi points. To
investigate the damping one has to replace the random phase approximation (RPA)
bare bubble by a sum of more complicated diagrams. It is shown here that a
better starting point than the bare RPA is to use the (conserving) linearized
time dependent Hartree-Fock equations, i.e. to perform a random phase
approximation (with) exchange
(RPAE) calculation. It is shown that the RPAE equation can be solved
analytically for the special form of the two-body interaction often used in the
Luttinger liquid framework. While (bare) RPA and RPAE agree for the case of a
strictly linear disperson there are qualitative differences for the case of the
usual nonrelativistic quadratic dispersion.Comment: 6 pages, 3 figures, misprints corrected; to appear in PRB7
Correlated sequential tunneling through a double barrier for interacting one-dimensional electrons
The problem of resonant tunneling through a quantum dot weakly coupled to
spinless Tomonaga-Luttinger liquids has been studied. We compute the linear
conductance due to sequential tunneling processes upon employing a master
equation approach. Besides the previously used lowest-order golden rule rates
describing uncorrelated sequential tunneling (UST) processes, we systematically
include higher-order correlated sequential tunneling (CST) diagrams within the
standard Weisskopf-Wigner approximation. We provide estimates for the parameter
regions where CST effects can be important. Focusing mainly on the temperature
dependence of the peak conductance, we discuss the relation of these findings
to previous theoretical and experimental results.Comment: replaced with the published versio
16-channnel Micro Magnetic Flux Sensor Array for IGBT Current Distribution Measurement
Current crowding of IGBT and power diode in a chip or among chips is a barrier to the realization of highly-reliable power module and power electronics system. Current crowding occurs because of the parasitic inductance, difference of chip characteristics or temperature imbalance among chips. Although current crowding among IGBT or power diode chips has been analysed on numerical simulations, no sensor with sufficiently high special resolution and fast measurement time has yet been demonstrated. Therefore, the author developed and demonstrated 16-channel flat sensitivity sensor array for IGBT current distribution measurement. The sensor array consists of tiny-scale film sensors with analog amps and shield case against noise. The array and digital calibration method will be applied for reliability analysis, designing and screening of IGBT modules.ESREF 2015, 26th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis, Oct 5-9, 2015, Centre de Congrès Pierre Baudis, Toulouse, Franc
High-throughput and Full Automatic DBC-Module Screening Tester for High Power IGBT
We developed a high-throughput screening tester for DBC-module of IGBT. The tester realizes a new screening test with current distribution in addition to a conventional switching test. It consists of a power circuit, a replaceable test head, sensor array module and digitizer with LabVIEW program. Therefore, all kinds of DBC-modules can be screened by switching the test head. The tester acquires magnetic field signals and displays GO/NOGO judgment automatically after digital calibration and signal processing in 10 seconds. It is expected to be applied for screening in a production line and analysis in order to prevent the failure of power modules.ESREF 2015, 26th European Symposium on Reliability of Electron Devices, Failure Physics and Analysis, Oct 5-9, 2015, Centre de Congrès Pierre Baudis, Toulouse, Franc
Infrared catastrophe and tunneling into strongly correlated electron systems: Exact solution of the x-ray edge limit for the 1D electron gas and 2D Hall fluid
In previous work we have proposed that the non-Fermi-liquid spectral
properties in a variety of low-dimensional and strongly correlated electron
systems are caused by the infrared catastrophe, and we used an exact functional
integral representation for the interacting Green's function to map the
tunneling problem onto the x-ray edge problem, plus corrections. The
corrections are caused by the recoil of the tunneling particle, and, in systems
where the method is applicable, are not expected to change the qualitative form
of the tunneling density of states (DOS). Qualitatively correct results were
obtained for the DOS of the 1D electron gas and 2D Hall fluid when the
corrections to the x-ray edge limit were neglected and when the corresponding
Nozieres-De Dominicis integral equations were solved by resummation of a
divergent perturbation series. Here we reexamine the x-ray edge limit for these
two models by solving these integral equations exactly, finding the expected
modifications of the DOS exponent in the 1D case but finding no changes in the
DOS of the 2D Hall fluid with short-range interaction. We also provide, for the
first time, an exact solution of the Nozieres-De Dominicis equation for the 2D
electron gas in the lowest Landau level.Comment: 6 pages, Revte
Spin effects in transport through non-Fermi liquid quantum dots
The current-voltage characteristic of a one dimensional quantum dot connected
via tunnel barriers to interacting leads is calculated in the region of
sequential tunneling. The spin of the electrons is taken into account.
Non-Fermi liquid correlations implying spin-charge separation are assumed to be
present in the dot and in the leads. It is found that the energetic distance of
the peaks in the linear conductance shows a spin-induced parity effect at zero
temperature T. The temperature dependence of the positions of the peaks depends
on the non-Fermi liquid nature of the system. For non-symmetric tunnel barriers
negative differential conductances are predicted, which are related to the
participation in the transport of collective states in the quantum dot with
larger spins. Without spin-charge separation the negative differential
conductances do not occur. Taking into account spin relaxation destroys the
spin-induced conductance features. The possibility of observing in experiment
the predicted effects are briefly discussed.Comment: 15 pages, 16 figures, accepted for publication on Physical Review
Quantum Scattering in Quasi-1D Cylindrical Confinement
Finite size effects alter not only the energy levels of small systems, but
can also lead to new effective interactions within these systems. Here the
problem of low energy quantum scattering by a spherically symmetric short range
potential in the presence of a general cylindrical confinement is investigated.
A Green's function formalism is developed which accounts for the full 3D nature
of the scattering potential by incorporating all phase-shifts and their
couplings. This quasi-1D geometry gives rise to scattering resonances and
weakly localized states, whose binding energies and wavefunctions can be
systematically calculated. Possible applications include e.g. impurity
scattering in ballistic quasi-1D quantum wires in mesoscopic systems and in
atomic matter wave guides. In the particular case of parabolic confinement, the
present formalism can also be applied to pair collision processes such as
two-body interactions. Weakly bound pairs and quasi-molecules induced by the
confinement and having zero or higher orbital angular momentum can be
predicted, such as p- and d-wave pairings.Comment: Extended version of quant-ph/050319
- …