Correlated Persistent Tunneling Currents in Glasses

Kettemann, Stefan; Fulde, Peter; Strehlow, Peter

doi:10.1103/physrevlett.83.4325

Cited by 60 publications

(77 citation statements)

References 15 publications

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“…A much more tenable explanation of the B 2 dependence is based on thermodynamic arguments of entropy and symmetry that in the leading order charged TLS or dipoles would yield a quadratic dependence of dissipation. 44,45 …”

Section: Magnetic Field Dependencementioning

confidence: 99%

Intrinsic dissipation in high-frequency micromechanical resonators

et al. 2002

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We report measurements of intrinsic dissipation in micron-sized suspended resonators machined from single crystals of galium arsenide and silicon. In these experiments on high-frequency micromechanical resonators, designed to understand intrinsic mechanisms of dissipation, we explore dependence of dissipation on temperature, magnetic field, frequency, and size. In contrast to most of the previous measurements of acoustic attenuation in crystalline and amorphous structures in this frequency range, ours is a resonant measurement; dissipation is measured at the natural frequencies of structural resonance, or modes of the structure associated with flexural and torsional motion. In all our samples we find a weakly temperature dependent dissipation at low temperatures. We compare and contrast our data to various probable mechanisms, including thermoelasticity, clamping, anharmonic mode-coupling, surface anisotropy and defect motion, both in bulk and on surface. The observed parametric dependencies indicate that the internal defect motion is the dominant mechanism of intrinsic dissipation in our samples.

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Section: Magnetic Field Dependencementioning

confidence: 99%

Intrinsic dissipation in high-frequency micromechanical resonators

et al. 2002

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“…This is the most controversial point and we are going to add some comments in this respect. Firstly, the large value of q has been taken as an indication that there is a coherent motion of tunneling particles taking place as the result of their mutual interaction 13,14 . As far as the low temperature physics of glasses is concerned the interaction between TLSs is an important issue which has been recently addressed as a dephasing mechanism in the relaxation of cold glasses 23 .…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The first theoretical attempt to explain the magnetic field dependence was based on the Aharanov-Bohm phase 13 . In this approach the dielectric permittivity is given by a generalized TLS where the magnetic field enters in the quantum mechanical phase of a tunneling charged particle in a Mexican hat potential.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Aharanov-Bohm phase on the magnetic-field dependence of two-pulse echoes in glasses at low temperatures

Akbari

Langari

2005

Phys. Rev. B

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The anomalous response of glasses in the echo amplitude experiment is explained in the presence of a magnetic field. We have considered the low energy excitations in terms of an effective two level system. The effective model is constructed on the flip-flop configuration of two interacting two level systems. The magnetic field affects the tunneling amplitude through the Aharanov-Bohm effect. The effective model has a lower scale of energy in addition to the new distribution of tunneling parameters which depend on the interaction. We are able to explain some features of echo amplitude versus a magnetic field, namely, the dephasing effect at low magnetic fields, dependence on the strength of the electric field, pulse separation effect and the influence of temperature. However this model fails to explain the isotope effects which essentially can be explained by the nuclear quadrupole moment. We will finally discuss the features of our results.

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“…Next, we found numerically the eigen values of the Hamiltonian and used Eqs. (14), (15), (16) to calculate the permittivity of a TLS with fixed parameters. 27 Then, numerical integration of the single TLS responses over all relevant parameters was performed to evaluate the effect of averaging.…”

Section: Permittivity Of Tunneling Systems With Quadrupole Interamentioning

confidence: 99%

Resonant susceptibility of dielectric glasses in magnetic field

2007

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The anomalous magnetic field dependence of dielectric properties of insulating glasses in the temperature interval 10mK < T < 50mK is considered. In this temperature range, the dielectric permittivity is defined by the resonant contribution of tunneling systems. The external magnetic field regulates nuclear spins of tunneling atoms. This regulation suppresses a nuclear quadrupole interaction of these spins with lattice and, thus, affects the dielectric response of tunneling systems. It is demonstrated that in the absence of an external magnetic field the nuclear quadrupole interaction b results in the correction to the permittivity δχ ∼ |b| /T in the temperature range of interest. An application of a magnetic field results in a sharp increase of this correction approximately by a factor of two when the Zeeman splitting m approaches the order of |b|. Further increase of the magnetic field results in a relatively smooth decrease in the correction until the Zeeman splitting approaches the temperature. This smooth dependence results from tunneling accompanied by a change of the nuclear spin projection. As the magnetic field surpasses the temperature, the correction vanishes. The results obtained in this paper are compared with experiment. A new mechanism of the low temperature nuclear spin-lattice relaxation in glasses is considered.

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Correlated Persistent Tunneling Currents in Glasses

Cited by 60 publications

References 15 publications

Intrinsic dissipation in high-frequency micromechanical resonators

Intrinsic dissipation in high-frequency micromechanical resonators

Effect of the Aharanov-Bohm phase on the magnetic-field dependence of two-pulse echoes in glasses at low temperatures

Resonant susceptibility of dielectric glasses in magnetic field

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