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1.
E. Kogan M. Auslender M. Kaveh 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,9(3):373-376
Localization and dephasing of conduction electrons in a low carrier density ferromagnet due to scattering on magnetic fluctuations
is considered. We claim the existence of the “mobility edge”, which separates the states with fast diffusion and the states
with slow diffusion; the latter is determined by the dephasing time. When the “mobility edge” crosses the Fermi energy a large
and sharp change of conductivity is observed. The theory provides an explanation for the observed temperature dependence of
conductivity in ferromagnetic semiconductors and manganite pyrochlores.
Received 17 January 1999 and Received in final form 12 March 1999 相似文献
2.
R. Egger A.O. Gogolin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(3):281-300
We derive the effective low-energy theory for single-wall carbon nanotubes including the Coulomb interactions among electrons.
The generic model found here consists of two spin-fermion chains which are coupled by the interaction. We analyze the theory using bosonization, renormalization-group techniques,
and Majorana refermionization. Several experimentally relevant consequences of the breakdown of Fermi liquid theory observed
here are discussed in detail, e.g., magnetic instabilities, anomalous conductance laws, and impurity screening profiles.
Received: 12 December 1997 / Revised: 9 March 1998 / Accepted: 12 March 1998 相似文献
3.
A. Tomiyama S. Suga A. Okiji 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):351-359
The elementary excitation spectrums for the Anderson model at finite temperatures are calculated by using the Bethe-ansatz
solution. The formulation is based on the method of Yang and Yang, which was developed for the one-dimensional boson systems
with the -function type interaction. We obtain the temperature dependence of the spin and the charge excitation spectrums. When the
impurity level lies deeply from the Fermi level and the Coulomb interaction is suitably large, the resonant peak structure
develops in the low energy region of the spin excitation spectrum and the hump structure grows around the impurity level of
the charge excitation spectrum with decreasing temperature.
Received: 21 January 1998 / Accepted: 17 March 1998 相似文献
4.
J.-J. Shi B.C. Sanders S.-H. Pan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(1):113-119
We calculate the electron-phonon scattering rate for an asymmetric double barrier resonant tunneling structure based on dielectric
continuum theory, including all phonon modes, and show that interface phonons contribute much more to the scattering rate
than do bulk-like LO phonons for incident energies which are approximately within an order of magnitude of the Fermi energy.
The maximum scattering rate occurs for incident electron energies near the quantum well resonance. Subband nonparabolicity
has a significant influence on electron-phonon scattering in these structures. We show that the relaxation time is comparable
to the dwell time of electrons in the quantum well for a typical resonant tunneling structure.
Received: 23 December 1997 / Revised: 24 March 1998 / Accepted: 9 March 1998 相似文献
5.
We present results for Kondo impurities in nanoscopic systems. Using Wilson's numerical renormalization group we analyze two different situations: an isolated system with a discrete spectrum of well-defined energy levels and a fixed number of electrons and a nanoscopic system weakly coupled to a macroscopic reservoir. In the latter case, new regimes not observed in macroscopic homogeneous systems are induced by the confinement of conduction electrons. These new confinement-induced regimes are very different depending on whether the Fermi energy is at resonance or between two quasi-bound states. 相似文献
6.
7.
A. Volmer S. Mukherji T. Nattermann 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):627-645
In anisotropic or layered superconductors thermal fluctuations as well as impurities induce a van der Waals (vdW) attraction
between flux lines, as has recently been shown by Blatter and Geshkenbein in the thermal case [#!BlatterGeshkenbein!#] and
by Mukherji and Nattermann in the disorder dominated case [#!NattermannMukherji!#]. This attraction together with the entropic
or disorder induced repulsion has interesting consequences for the low field phase diagram. We present two derivations of
the vdW attraction, one of which is based on an intuitive picture, the other one following from a systematic expansion of
the free energy of two interacting flux lines. Both the thermal and the disorder dominated case are considered. In the thermal
case in the absence of disorder, we use scaling arguments as well as a functional renormalization of the vortex-vortex interaction
energy to calculate the effective Gibbs free energy on the scale of the mean flux line distance. We discuss the resulting
low field phase diagram and make quantitative predictions for pure BiSCCO (Bi2Sr2CaCu2O8). In the case with impurities, the Gibbs free energy is calculated on the basis of scaling arguments, allowing for a semi-quantitative
discussion of the low-field, low-temperature phase diagram in the presence of impurities.
Received: 9 February 1998 / Accepted: 17 April 1998 相似文献
8.
M. Stebelski M. Lisowski E. Zipper 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(2):215-222
Quantum coherence of electrons interacting via the magnetostatic coupling and confined to a mesoscopic cylinder is discussed. The electromagnetic response of a system is
studied. It is shown that the electromagnetic kernel has finite low frequency limit what implies infinite conductivity. It
means that part of the electrons is in a coherent state and the system can be in general described by a two-fluid model. The
coherent behavior is determined by the interplay between finite size effects and the correlations coming from the magnetostatic
interactions (the interaction is considered in the mean field approximation). The related persistent currents depend on the
geometry of the Fermi surface. If the Fermi surface has some flat portions the self-sustaining currents can be obtained. The
relation of the quantum coherent state in mesoscopic cylinders to other coherent phenomena is discussed.
Received: 9 July 1997 / Revised: 19 September 1997 / Accepted: 4 November 1997 相似文献
9.
K. Pomorski K. Dietrich 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):353-364
We investigate the existence of stable charged metallic bubbles using the shell correction method. We find that for a given
mesoscopic system of n atoms of a given metal and (positive) elementary charges, a metallic bubble turns out to have a lower total energy than a compact spherical cluster,
whenever the charge number q is larger than a critical charge number qc. For a magic number (n-q) of free electrons, the spherical metallic bubble may become stable against fission.
Received: 17 November 1997 / Revised: 28 May 1998 / Accepted: 20 July 1998 相似文献
10.
A. Takahashi H. Shiba 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):413-417
The optical absorption in ferromagnetic metal La1-xSrxMnO3 is anomalous; it has a wide-range absorption up to about 1 eV even at zero temperature. Since 3d electrons in La1-xSrxMnO3 partially fill doubly degenerate eg orbitals, the orbital degrees of freedom are crucial to understand this metallic system. We argue that the interband transition
within eg orbitals is important in the optical absorption. The optical spectrum is modified also by the inter-orbital Coulomb interaction.
We have examined perturbatively the effect of the Coulomb interaction on the spectrum. Available experiments are discussed
by comparing with the present results.
Received: 13 February 1998 / Accepted: 17 March 1998 相似文献
11.
M. Zacchigna J. Almeida I. Vobornik G. Margaritondo D. Malterre B. Malaman M. Grioni 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,2(4):463-467
We exploited resonant photoemission at the Ce absorption edge to investigate the Ce 4f states in . High resolution spectra reveal, near the Fermi level, the characteristic fine structure of intermediate valence Ce compounds.
The spectral lineshape is consistent with the typical “Kondo” character of CePd, but the prominent ionization peak is found at the unusually low binding energy of 1 eV. We briefly discuss the implications of these observations.
Received: 13 October 1997 / Accepted: 21 January 1998 相似文献
12.
O. Toulemonde F. Studer A. Barnabé A. Maignan C. Martin B. Raveau 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(2):159-167
The XAS study at Cr, Co, Ni and Mn K-edges was performed for the doped CMR manganites Ln0.5Ca0.5Mn1-xBxO3 with Ln=La, Nd, Sm and B= Cr, Co, Ni (), on the samples that were studied previously for their ferromagnetic-metallic to antiferromagnetic-insulator transition.
We observed that the formal charges of the doping elements are Ni2+, Co2+ and Cr3+. It is also evidenced that the average formal charge of the manganese is increased after doping, in agreement with the charge
compensation keeping “O3” stoichiometry. These results suggest that the doping elements participate directly to the band structure.
Received: 9 January 1998 / Received in final form: 6 April 1998 / Accepted: 7 April 1998 相似文献
13.
We show how Fermi liquid theory results can be systematically recovered using a renormalization group (RG) approach. Considering
a two-dimensional system with a circular Fermi surface, we derive RG equations at one-loop order for the two-particle vertex
function in the limit of small momentum () and energy () transfer and obtain the equation which determines the collective modes of a Fermi liquid. The density-density response function
is also calculated. The Landau function (or, equivalently, the Landau parameters F
l
s
and F
l
a
) is determined by the fixed point value of the -limit of the two-particle vertex function (). We show how the results obtained at one-loop order can be extended to all orders in a loop expansion. Calculating the quasi-particle
life-time and renormalization factor at two-loop order, we reproduce the results obtained from two-dimensional bosonization
or Ward Identities. We discuss the zero-temperature limit of the RG equations and the difference between the Field Theory
and the Kadanoff-Wilson formulations of the RG. We point out the importance of n-body () interactions in the latter.
Received: 27 June 1997 / Received in final form: 17 December 1997 / Accepted: 26 January 1998 相似文献
14.
A.A. Zvyagin 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(3):351-360
The behavior of charge and spin persistent currents in an integrable lattice ring of strongly correlated electrons with a
magnetic impurity is exactly studied. Our results manifest that the oscillations of charge and spin persistent currents are
similar to the ones, earlier obtained for integrable continuum models with a magnetic impurity. The difference is due to two
(instead of one) Fermi velocities of low-lying excitations. The form of oscillations in the ground state is “saw-tooth”-like,
generic for any multi-particle coherent one-dimensional models. The integrable magnetic impurity introduces net charge and
spin chiralities in the generic integrable lattice system, which determine the initial phase shifts of charge and spin persistent
currents. We show that the magnitude of the charge persistent current in the generic Kondo situation does not depend on the
parameters of the magnetic impurity, unlike the (magneto)resistivity of transport currents.
Received 30 January 2003 / Received in final form 12 March 2003 Published online 11 April 2003
RID="a"
ID="a"e-mail: zvyagin@fy.chalmers.se 相似文献
15.
16.
H. Beckmann G. Bergmann 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(3):495-502
Sandwiches made from Fe and Cs films are investigated as a function of the magnetic field and the Cs thickness. Conduction
electrons which cross from the Fe to the Cs are marked by a drift velocity component perpendicular to the electric field.
The anomalous Hall effect in the Fe provides this “non-diagonal” kick to the electrons that cross from the Fe into the Cs.
The ballistic propagation of the conduction electrons can be monitored as a function of the Cs film thickness. The free propagation
into the Cs is measured in terms of the non-diagonal conductance Lxy which we denote as the “induced anomalous Hall conductance”L
xy
0. For a normal (non-magnetic) metal in contact with Fe, Lxy increases with the thickness of the normal metal until the film thickness exceeds (half) the mean free path of the conduction
electrons. For Cs on top of Fe the induced anomalous Hall conductance increases up to a Cs coverage of about 100 A, then,
in contrast to other non-magnetic metals, L
xy
0 decreases for larger Cs coverage and approaches zero. This behavior cannot be explained with the free electron model. The
strange behavior of the induced AHC in Cs films adds an even more challenging mystery to the already poorly understood properties
of thin Cs films. These results defy explanation in the free electron model.
Received 29 April 1999 and Received in final form 10 July 1999 相似文献
17.
P. Schlottmann A.A. Zvyagin 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):325-335
We consider the one-dimensional t
-
J model, which consists of electrons with spin S on a lattice with nearest neighbor hopping t constrained by the excluded multiple occupancy of the lattice sites and spin-exchange J between neighboring sites. The model is integrable at the supersymmetric point, J
=
t. Without spoiling the integrability we introduce an Anderson-like impurity of spin S (degenerate Anderson model in the limit), which interacts with the correlated conduction states of the host. The lattice model is defined by the scattering
matrices via the Quantum Inverse Scattering Method. We discuss the general form of the interaction Hamiltonian between the impurity and
the itinerant electrons on the lattice and explicitly construct it in the continuum limit. The discrete Bethe ansatz equations
diagonalizing the host with impurity are derived, and the thermodynamic Bethe ansatz equations are obtained using the string
hypothesis for arbitrary band filling as a function of temperature and external magnetic field. The properties of the impurity
depend on one coupling parameter related to the Kondo exchange coupling. The impurity can localize up to one itinerant electron
and has in general mixed valent properties. Groundstate properties of the impurity, such as the energy, valence, magnetic
susceptibility and the specific heat coefficient, are discussed. In the integer valent limit the model reduces to a Coqblin-Schrieffer impurity.
Received: 31 December 1997 / Accepted: 17 March 1998 相似文献
18.
M. Sassetti B. Kramer 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(3):357-367
The Raman spectra of quantum wires in the region of electronic intra-band excitations are investigated using one- and two-band
models based on the Luttinger approximation with spin. Structures related to charge and spin density modes are identified,
and analyzed with respect to their behavior with photon energy and temperature. It is found that the low-energy peaks in the
polarized spectra, close to resonance that are commonly assigned to “single particle excitations”, can be interpreted as the
signature of spin density excitations. A broad structure in the resonant depolarized spectrum is predicted above the frequency
of the spin density excitations. This is due to simultaneous but independent propagation of spin and charge density modes.
The results, when compared with experiment, show, that the electronic collective excitations of quantum wires at low energies
are characteristic for a non-Fermi liquid.
Received: 25 March 1998 / Accepted: 3 June 1998 相似文献
19.
M. Henkel D. Karevski 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):787-792
The effect of point defects on persistent currents in mesoscopic rings is studied in a simple tight-binding model. Using an
analogy with the treatment of the critical quantum Ising chain with defects, conformal invariance techniques are employed
to relate the persistent current amplitude to the Hamiltonian spectrum just above the Fermi energy. From this, the dependence
of the current on the magnetic flux is found exactly for a ring with one or two point defects. The effect of an aperiodic
modulation of the ring, generated through a binary substitution sequence, on the persistent current is also studied. The flux-dependence
of the current is found to vary remarkably between the Fibonacci and the Thue-Morse sequences.
Received: 4 March 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
20.
S. Martin J. Bernard L. Chen A. Denis J. Désesquelles 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):1-6
Electron capture by Ar8+ in collisions with C60 fullerene has been investigated using coincident measurements of the number n of ejected electrons, the mass and charge of multicharged Cr+
60
recoil ions and their fragments Ci+
m and the final charge state of outgoing projectiles Ar(8-s)+ (). The number of captured electrons r is the sum of the numbers of stabilized and emitted electrons: r
=
n
+
s. The ratio n
/
s decreases by a factor three with s increasing from 1 to 7 showing that the multiply excited states populated by capture of a large number of electrons are rather
stable against auto-ionisation. Each kinetic energy spectrum of Ar+ and Ar2+ projectiles is composed of two peaks which we attribute to collisions “inside” and “outside” the C60 cage. The measured energy shift of the projectile keV is consistent with the corresponding energy loss keV in a carbon foil with an equivalent thickness. Inside collisions are characterized by a strong dissociation of recoil
ions into light monocharged fragments and by a high multiplicity of ejected electrons.
Received: 25 March 1998 / Received in final form and Accepted: 9 June 1998 相似文献