共查询到20条相似文献,搜索用时 15 毫秒
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Y.J. Uemura 《Solid State Communications》1980,36(4):369-372
The muon spin relaxation function is calculated in a fluctuating random dilute spin system, and the effect of Edwards—Anderson's order parameter is considered in a time-dependent treatment. The results demonstrate the unique capability of zero-field μSR probing spin glasses. 相似文献
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μSR is shown to be a sensitive probe of fluctuating internal magnetic fields in geometrically frustrated magnets. The usefulness of μSR in these systems is illustrated in the case of pyrochlores, in which the antiferromagnetically coupled ions occupy a lattice of corner sharing tetrahedra. Remarkably, one observes a type of spin freezing in Y2Mo2O7 and Tb2Mo2O7 which is similar to that seen in conventional spin glasses, even though there is no detectable structural disorder. Unlike ordinary spin glasses these geometrically frustrated antiferromagnets display unusual low temperature spin dynamics which persist down to the lowest accessible temperatures. 相似文献
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Muon spin relaxation (SR) and neutron spin echo (NSE) measurements of magnetic ion correlation times and correlation functions in the spin glass systemsCuMn,AgMn, andAuFe are compared. It is found that theSR and NSE measurements are in excellent agreement both above and below the spin-glass freezing temperatures. The experimental results are compared to recent theories of spin-glass dynamics.We are grateful to D.L. Huber and R.E. Walstedt for stimulating discussions. This work was performed under the auspices of the U.S. Department of Energy, and was also supported by the U.S. National Science Foundation, Grant No. DMR-8115543. 相似文献
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Amasha S Maclean K Radu IP Zumbühl DM Kastner MA Hanson MP Gossard AC 《Physical review letters》2008,100(4):046803
We demonstrate electrical control of the spin relaxation time T1 between Zeeman-split spin states of a single electron in a lateral quantum dot. We find that relaxation is mediated by the spin-orbit interaction, and by manipulating the orbital states of the dot using gate voltages we vary the relaxation rate W identical withT1(-1) by over an order of magnitude. The dependence of W on orbital confinement agrees with theoretical predictions, and from these data we extract the spin-orbit length. We also measure the dependence of W on the magnetic field and demonstrate that spin-orbit mediated coupling to phonons is the dominant relaxation mechanism down to 1 T, where T1 exceeds 1 s. 相似文献
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We present a quantitative analysis of the temperature dependence of the muon spin relaxation rate measured in simple magnets.
We consider the low temperature, critical and high temperature regimes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Ming-Liang Hu Xiao-Qiang Xi Chang-Xing Li Han-Zhang Qu 《Physica B: Condensed Matter》2009,404(1):16-21
By analytically solving the master equation, we examine entanglement dynamics of the two-qubit spin system coupled via the XY interaction and in the presence of population relaxation. We found that the entanglement dynamical behaviors are very sensitive to different initialized states. Particularly, for initial states ?=(|01〉〈01|+|10〉〈10|)/2 and ?=(|00〉〈00|+|11〉〈11|)/2, a combination of the XY coupling with the population relaxation can even be used to enhance the entanglement. Moreover, we show that among different initially separable states, ?=|01〉〈01| and ?=|10〉〈10| are more robust in generating pairwise entanglement. 相似文献
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Using spin-echo NMR techniques we study the transverse spin relaxation of hyperpolarized liquid 129Xe in a spherical cell. We observe an instability of the transverse magnetization due to dipolar fields produced by liquid 129Xe, and find that imperfections in the pi pulses of the spin-echo sequence suppress this instability. A simple perturbative model of this effect is in good agreement with the data. We obtain a transverse spin relaxation time of 1300 sec in liquid 129Xe, and discuss applications of hyperpolarized liquid 129Xe as a sensitive magnetic gradiometer and for a permanent electric dipole moment search. 相似文献
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The changes in the spin depolarization length in zinc-blende semiconductors when an external component of correlated noise is added to a static driving electric field are analyzed for different values of field strength, noise amplitude and correlation time. Electron dynamics is simulated by a Monte Carlo procedure which takes into account all the possible scattering phenomena of the hot electrons in the medium and includes the evolution of spin polarization. Spin depolarization is studied by examining the decay of the initial spin polarization of the conduction electrons through the D'yakonov-Perel process, the only relevant relaxation mechanism in III-V crystals. Our results show that, for electric field amplitudes lower than the Gunn field, the dephasing length shortens with increasing noise intensity. Moreover, a nonmonotonic behavior of spin depolarization length with the noise correlation time is found, characterized by a maximum variation for values of noise correlation time comparable with the dephasing time. Instead, in high field conditions, we find that, critically depending on the noise correlation time, external fluctuations can positively affect the relaxation length. The influence of the inclusion of the electron-electron scattering mechanism is also shown and discussed. 相似文献
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Balocchi A Duong QH Renucci P Liu BL Fontaine C Amand T Lagarde D Marie X 《Physical review letters》2011,107(13):136604
The electron spin dynamics in (111)-oriented GaAs/AlGaAs quantum wells is studied by time-resolved photoluminescence spectroscopy. By applying an external electric field of 50 kV/cm a two-order of magnitude increase of the spin relaxation time can be observed reaching values larger than 30 ns; this is a consequence of the electric field tuning of the spin-orbit conduction band splitting which can almost vanish when the Rashba term compensates exactly the Dresselhaus one. The measurements under a transverse magnetic field demonstrate that the electron spin relaxation time for the three space directions can be tuned simultaneously with the applied electric field. 相似文献
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Zheng Sun Z.Y. Xu X.Z. Ruan Yang Ji B.Q. Sun M. Wang H.Q. Ni 《Solid State Communications》2007,143(3):158-160
Using time-resolved photoluminescence and time-resolved Kerr rotation spectroscopy, we explore the unique electron spin behavior in an InAs submonolayer sandwiched in a GaAs matrix, which shows very different spin characteristics under resonant and non-resonant excitations. While a very long spin relaxation lifetime of a few nanoseconds at low temperature is observed under non-resonant excitation, it decreases dramatically under resonant excitation. These interesting results are attributed to the difference in electron-hole interactions caused by non-geminate or geminate capture of photo-generated electron-hole pairs in the two excitation cases, and provide a direct verification of the electron-hole spatial correlation effect on electron spin relaxation. 相似文献
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Khaneja N Reiss T Kehlet C Schulte-Herbrüggen T Glaser SJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,172(2):296-305
In this paper, we introduce optimal control algorithm for the design of pulse sequences in NMR spectroscopy. This methodology is used for designing pulse sequences that maximize the coherence transfer between coupled spins in a given specified time, minimize the relaxation effects in a given coherence transfer step or minimize the time required to produce a given unitary propagator, as desired. The application of these pulse engineering methods to design pulse sequences that are robust to experimentally important parameter variations, such as chemical shift dispersion or radiofrequency (rf) variations due to imperfections such as rf inhomogeneity is also explained. 相似文献
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We develop a semiclassical theory for spin-dependent quantum transport to describe weak (anti)localization in quantum dots with spin-orbit coupling. This allows us to distinguish different types of spin relaxation in systems with chaotic, regular, and diffusive orbital classical dynamics. We find, in particular, that for typical Rashba spin-orbit coupling strengths, integrable ballistic systems can exhibit weak localization, while corresponding chaotic systems show weak antilocalization. We further calculate the magnetoconductance and analyze how the weak antilocalization is suppressed with decreasing quantum dot size and increasing additional in-plane magnetic field. 相似文献
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Molecular reorientations and internal conformational transitions of an aligned chiral liquid crystal (LC) 10B1M7 are studied by means of deuterium spin-lattice relaxation in its smectic A (SmA) and smectic C* (SmC*) phase. The motional model which is applicable to uniaxial phases of many LCs is found to be adequate even when the phase is a tilted SmC* phase. The deuterium NMR spectrum in this phase cannot discern rotations of the molecular director about the pitch axis. The basic assumption is that the phase biaxiality is practically unobservable. However, the relaxation rates can be accounted for by the tilt angle between the molecular director and the layer normal in the SmC* phase. The tumbling motion appears to show a higher activation energy upon entering from the uniaxial SmA into the SmC* phase. 相似文献
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Upali A. Jayasooriya John A. Stride Georgina M. Aston Gareth A. Hopkins Stephen F.J. Cox Stephen P. Cottrell Christopher A. Scott 《Hyperfine Interactions》1997,106(1-4):27-32
LF‐Muon Spin Relaxation data are reported for the organometallic compounds Pb(C6H5)4, (C6H6)Cr(CO)3 and (C5H5)2Ru. In each case the change in relaxation rate with temperature shows a peak analogous to the T_1 minimum in NMR. The activation
parameters were calculated, and the mechanism of muon spin relaxation in the case of (C6H6)Cr(CO)3 is shown to be the reorientation motion of the benzene ring.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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V. Meden J. Fricke C. Wöhler K. Schönhammer 《Zeitschrift für Physik B Condensed Matter》1995,99(1):357-365
We present the exact solution for the time evolution of the electron and phonon momentum distribution for a one-dimensional
polaron model with alinear electronic energy dispersion. The electron momentum distribution is shown to obey aMarkovian quantum kinetic equation. Numerical results for the polaron model are compared to the corresponding exact results, when the
negative momentum states are filled in the initial state. The presence of this Fermi sea modifies the dynamics except in the
short time regime. The different, long time dynamics might show up in comparison of hot electron relaxation of undoped and
doped semiconductors. 相似文献
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V. Meden J. Fricke C. Wöhler K. Schönhammer 《Zeitschrift für Physik B Condensed Matter》1995,99(3):357-365
We present the exact solution for the time evolution of the electron and phonon momentum distribution for a one-dimensional polaron model with alinear electronic energy dispersion. The electron momentum distribution is shown to obey aMarkovian quantum kinetic equation. Numerical results for the polaron model are compared to the corresponding exact results, when the negative momentum states are filled in the initial state. The presence of this Fermi sea modifies the dynamics except in the short time regime. The different, long time dynamics might show up in comparison of hot electron relaxation of undoped and doped semiconductors. 相似文献
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The apparently homogeneous E.S.R. spectra of solution manganous ions are interpreted in terms of a sum of degenerate lorentzian lineshapes with different widths. The existence of a distribution of linewidths instead of a single linewidth, is interpreted assuming that the electron spin relaxation is dominated by rotation of a static zero-field splitting tensor caused by slow configurational changes of the ionic environment, including first and second solvation spheres. Typical configurational lifetimes of the second solvation sphere were found to be τ k ~ 10-9 s. Details of the ionic structure and dynamics are discussed. 相似文献