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1.
A model of spin relaxation of Kondo lattices is proposed to explain the angular dependence of the electron spin resonance (ESR) parameters in the heavy fermion compounds Y bIr(2)Si(2) and Y bRh(2)Si(2). A perturbational scaling approach reveals a collective spin motion of Yb?ions with conduction electrons in the bottleneck regime. A common energy scale due to the Kondo effect regulates the temperature dependence of different kinetic coefficients to result in a mutual cancelation of all divergent parts in a collective spin mode. The angular dependence of the ESR intensity, linewidth and resonant frequency is shown to be in good agreement with experimental data on Y bIr(2)Si(2) and Y bRh(2)Si(2). In particular, the unexpectedly weak dependence of the ESR intensity on the orientation of the microwave magnetic field agrees with the properties of the discussed model. 相似文献
2.
Sichelschmidt J Ivanshin VA Ferstl J Geibel C Steglich F 《Physical review letters》2003,91(15):156401
We report an electron spin resonance (ESR) study on single crystals of the heavy fermion metal YbRh2Si2 which shows pronounced non-Fermi liquid behavior related to a close antiferromagnetic quantum critical point. It is shown that the observed ESR spectra can be ascribed to a bulk Yb3+ resonance. This is the first observation of ESR of the Kondo ion itself in a dense Kondo lattice system. The ESR signal occurs below the Kondo temperature (T(K)) which thus indicates the existence of large unscreened Yb3+ moments below T(K). We observe the spin dynamics as well as the static magnetic properties of the Yb3+ spins to be consistent with the results of nuclear magnetic resonance and magnetic susceptibility. 相似文献
3.
Holanda LM Vargas JM Iwamoto W Rettori C Nakatsuji S Kuga K Fisk Z Oseroff SB Pagliuso PG 《Physical review letters》2011,107(2):026402
Electron spin resonance (ESR) can probe conduction electrons (CE) and local moment (LM) spin systems in different materials. A CE spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR can be seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a remarkable and unprecedented ESR signal in the heavy-fermion superconductor β-YbAlB? [S. Nakatsuji et al., Nature Phys. 4, 603 (2008)] which behaves as a CESR at high temperatures and acquires characteristics of the Yb3? LM ESR at low temperature. This dual behavior strikes as an in situ unique observation of the Kondo quasiparticles in a quantum critical regime. The proximity to a quantum critical point may favor the appearance of this dual character of the ESR signal in β-YbAlB?. 相似文献
4.
V. G. Kytin B. M. Bulychev A. V. Krechetov E. A. Konstantinova V. A. Kulbachinskii R. A. Lunin 《Applied magnetic resonance》2008,33(1-2):177-184
Paramagnetic centers in heterofullerides with the composition A2MC60 and AM2C60 (A = K, Rb, M = Mg, Be) were investigated by the electron spin resonance (ESR) method. It was found that the ESR signal can
be interpreted as a composition of two lines with different temperature dependence of ESR absorption magnitude. This gives
an evidence of the presence of at least two different types of paramagnetic centers. Centers of the first type behave as localized
spins, while the rest can be interpreted as conduction electrons.
Authors' address: Vladimir A. Kulbachinskii, Physics Faculty, M. V. Lomonosov Moscow State University, Leninskie Gory, Moscow
119991, Russian Federation 相似文献
5.
B. I. Kochelaev S. I. Belov A. M. Skvortsova A. S. Kutuzov J. Sichelschmidt J. Wykhoff C. Geibel F. Steglich 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):485-489
We develop a theoretical basis for understanding the spin relaxation processes in Kondo lattice systems with heavy fermions
as experimentally observed by electron spin resonance (ESR). The Kondo effect leads to a common energy scale that regulates
a logarithmic divergence of different spin kinetic coefficients and supports a collective spin motion of the Kondo ions with
conduction electrons. We find that the relaxation rate of a collective spin mode is greatly reduced due to a mutual cancellation
of all the divergent contributions even in the case of the strongly anisotropic Kondo interaction. The contribution to the
ESR linewidth caused by the local magnetic field distribution is subject to motional narrowing supported by ferromagnetic
correlations. The developed theoretical model successfully explains the ESR data of YbRh2Si2 in terms of their dependence on temperature and magnetic field. 相似文献
6.
Nesting in a semimetal can lead to an excitonic-insulator state with spontaneous coherence between conduction and valence bands and a gap for charged excitations. We present a theory of the ferromagnetic state that occurs when the density of electrons in the conduction band and holes in the valence band differ. We find an unexpectedly rich doping-field phase diagram and an unusual collective excitation spectrum that includes two gapless collective modes. We predict regions of doping and external field in which phase-separated condensates of electrons and holes with parallel spins and opposing spins coexist. 相似文献
7.
We report on the low temperature electron spin resonance (ESR) properties of ultra-small (0.45?nm) double walled carbon nanotubes (DWCNTs) embedded in zeolite nanochannels. An isotropic ESR signal is observed at g(c)?=?2.002?77 with the spin density (S?=?1/2)?~?10(19)?g(-1), which is suggested to originate from the carbon related point defects in the DWCNTs. Measurements of the ESR line width and signal intensity as a function of temperature indicate that the spins are of a localized nature as opposed to the conduction type electrons observed in large diameter CNTs. The results are consistent with the suggestion that electrons are trapped at interstitial defects. The observed linear frequency dependence of the ESR line width of embedded DWCNTs points to 'strain' as the prime source of broadening. By contrast, the study of free standing DWCNTs shows the presence of a distinctly superlinear frequency dependence of the signal width at low temperatures. The possible origin of the frequency dependence is discussed. 相似文献
8.
Wahl P Simon P Diekhöner L Stepanyuk VS Bruno P Schneider MA Kern K 《Physical review letters》2007,98(5):056601
The magnetic coupling between single Co atoms adsorbed on a copper surface is determined by probing the Kondo resonance using low-temperature scanning tunneling spectroscopy. The Kondo resonance, which is due to magnetic correlation effects between the spin of a magnetic adatom and the conduction electrons of the substrate, is modified in a characteristic way by the coupling of the neighboring adatom spins. Increasing the interatomic distance of a Cobalt dimer from 2.56 to 8.1 A we follow the oscillatory transition from ferromagnetic to antiferromagnetic coupling. Adding a third atom to the antiferromagnetically coupled dimer results in the formation of a collective correlated state. 相似文献
9.
V. A. Ivanshin T. O. Litvinova A. A. Sukhanov D. A. Sokolov M. C. Aronson 《JETP Letters》2009,90(2):116-119
An electron spin resonance (ESR) signal was observed in a concentrated Kondo lattice, Heusler alloy YbRh2Pb. It is attributed to the combined effect of the 4f local magnetic moments of Yb3+ and conduction electrons. It is shown that the significant broadening and disappearance of the ESR line at temperatures above 20 K is caused by the processes of the spin-lattice relaxation of the Yb3+ ions through the first excited Stark doublet with an activation energy Δ ≈ 73.5 K. A comparison of the ESR data for YbRh2Pb and some other undoped intermetallic compounds based on ytterbium, cerium, and europium indicates that hybridized electronic states occurring as the result of hybridization between the localized 4f electrons and the collectivized conduction electrons constitute a fundamentally new source of ESR. 相似文献
10.
An electron spin resonance (ESR) method is applied to a pentacene field-effect device to investigate gate-induced hole carriers in such devices. Clear field-induced ESR signals are observed, demonstrating that all of the field-injected carriers have S = 1/2 spins. Anisotropic ESR signals due to unpaired pi electrons show the molecular orientation at the interface in the devices. The spatial extent of the spin density distribution (wave function) of the carriers is evaluated from the ESR linewidth, accounting for the hyperfine structure, to be of the order of 10 molecules. 相似文献
11.
A review is given of newly developed pulsed Electron Spin Resonance (ESR) methods for dynamic polarization of nuclear spins.
The application of two of these methods, Nuclear Orientation Via Electron spin Locking (NOVEL) and the Integrated Solid Effect
(ISE), for the polarization of nuclear spins in semiconductors is discussed in more detail. It is proposed to use these methods
to study the ESR spectrum of unpaired electrons in the vicinity of muons that are bound in a solid. Thus, ESR would be observed
with a sensitivity which is enhanced by about ten orders of magnitude compared to conventional ESR. 相似文献
12.
Q. Ai Y. Li G. L. Long C. P. Sun 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(2):293-300
We theoretically explore the possibility of creating spin
entanglement by simultaneously coupling two electronic spins to a
nuclear ensemble. By microscopically modeling the spin ensemble as a
single mode boson field, we use the time-dependent Fr?hlich
transformation (TDFT) method developed recently [Y. Li, C. Bruder, C.P. Sun, Phys. Rev. A 75, 032302 (2007)] to calculate
the effective coupling between the two spins. Our investigation
shows that the total system realizes a solid state based
architecture for cavity QED. Exchanging such kind of effective boson
in a virtual process can result in an effective interaction between
two spins. It is discovered that a maximum entangled state can be
obtained when the velocity of the electrons matches the initial
distance between them in a suitable way. Moreover, we also study how
the number of collective excitations influences the entanglement. It
is shown that the larger the number of excitation is, the less the
two spins entangle each other. 相似文献
13.
14.
A. D. Efimov V. M. Mikhajlov 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(8):857-862
Low-lying collective quadrupole states in four N = 70 isotones are analyzed within interacting boson model (IBM1) using parameters calculated on the basis of a microscopic quasiparticle theory that considers variation of the superconducting and collective quadrupole properties with increasing excitation energies and spins. 相似文献
15.
The magnetic resonance line of conduction electrons in solids may exhibit bistable hysteresis if several conditions are fulfilled. Its mechanism is presented and the manifestation of bistability in the ESR of conduction electrons in single crystal and polycrystalline samples is discussed. The characteristics of the dynamics of the bistability show that bistable resonance can be assimilated to one-dimensional overdamped motion of the spin system in the nuclear field space, driven by a bistable potential. It is shown for the first time that noise acting on this bistable resonance can create order, by the phenomenon of stochastic resonance. 相似文献
16.
K. W. Becker 《Physica A》1987,140(3):521-553
We discuss the critical dynamics of a system of localized spins interacting with conduction electrons via an isotropic exchange coupling between the respective spin densities. It is shown that the elimination of the conduction electrons by an adiabatic approximation is not allowed for small wave vectors. The quantum mechanical Fokker-Planck equation derived in a previous paper is used to investigate the renormalization of the kinetic coefficients due to nonlinear mode coupling contributions. 相似文献
17.
Joynt R 《Physical review letters》2000,84(17):3954-3957
A theory is put forward that the electronic phase transition at 0.2 K in Ni-doped Bi2Sr2CaCu2O8 is a result of the formation of a spin density wave in the system of Ni impurities. The driving force for the transition is the exchange interaction between the impurity spins and the spins of the conduction electrons. This creates a small gap at two of the four nodes of the superconducting gap. The effect is to reduce the thermal conductivity by a factor of 2, as observed. 相似文献
18.
The system of electrons on liquid helium is an interesting candidate to implement quantum computation, due to the long coherence times of the qubits encoded by the electronic spins. In order to implement the quantum logic operations between the spins, we propose here a configuration, similarly to the cooled ions in a trap, to couple the distant electrons via manipulating their center of mass (CM) vibrations. First, we show that the electrons could be confined in a common harmonic oscillator potential by using an electrostatic field. Then, with a single current pulse (applied on the micro-electrode below the liquid helium) the distant electronic spins can be coupled simultaneously to the CM mode. Finally, by adiabatically eliminating the CM mode, effective interaction between the distant spins is induced for implementing the desired quantum computing. 相似文献
19.
Low temperature ESR spectra of cis-rich and trans-rich polyacetylene, lightly doped with pentafluorides (AsF5, SbF5) exhibit two clearly distinguishable ESR lines. Detailed studies of these two lines as a function of temperature, doping concentration and microwave power indicate that one of these lines originates from localized spins, the other from conduction electrons. The concentration of the localized spins, generally speaking, decreases with doping. The Pauli-like susceptibility associated with the conduction electrons changes from 1.5×10–7 to 15×10–7 emu·cm3/mole for various doping levels and correlates with the conductivity of the same samples. The longitudinal relaxation time of the localized spins in doped trans-rich was found to beT
1100 s at low temperatures, consistent with values of others in undoped trans rich. The temperature dependence of the homogeneous transverse relaxationT
2 of the localized spins in doped trans-rich polyacetylene is similar to that of undoped trans polyacetylene. These facts show that the localized spins originate from undoped regions of the doped polyacetylene, perhaps due to inhomogenous doping. Our results are consistent with either formation of metallic islands, or, probably more, with impurity band conduction in strongly disordered semiconductors. 相似文献
20.
A. A. Kosov 《Russian Physics Journal》1978,21(8):1012-1015
Coupled equations are obtained for the transverse dynamic susceptibilities of paramagnetic impurities and conduction electrons in an impure superconductor of the second kind in a magnetic field somewhat higher than the upper critical field Hc2 under the conditions of fluctuation pairing of the conduction electrons. The fluctuation corrections to the shift and line-width of the magnetic resonance are determined in the paramagnetic impurities and the conduction electrons. The magnetic resonance parameters are investigated under the conditions of coupled motion of the magnetic moments of the impurities and the conduction electron spins in the presence of superconducting fluctuations.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 41–45, August, 1978. 相似文献