Origin of the tunneling states in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">SiO</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

Laermans, C.; Keppens, Veerle

doi:10.1103/physrevb.51.8158

Cited by 29 publications

(18 citation statements)

References 16 publications

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“…The incoherent tunnelling is characteristic for two-level systems, which have a strong coupling with phonons. It was shown [12] that such systems are resided not in amorphous clusters created by fast neutrons, but in slightly disturbed crystalline part of irradiated quartz. Their density rapidly grows for irradiation doses higher 1 × 10 19 n/cm 2 .…”

Section: Resultsmentioning

confidence: 97%

“…For the sample N3 it was calculated from ultrasound attenuation [18] using an experimental relation C(vel) = C(att)/2 and it is equal to 10 × 10 −6 . For the samples N4, N5 the values of C were obtained from the slope of the logarithmic temperature dependence of the ultrasound velocity [19,12] and they are equal to 21 × 10 −6 and 49 × 10 −6 , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Low-temperature thermal and acoustic properties of the neutron-irradiated quartz crystals were found very similar to amorphous solids [10,11,12]. Moreover, it was shown that the disorder is created in a natural way and one can produce different degrees of disorder varying the irradiation dose.…”

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confidence: 95%

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Ultrasound velocity in neutron‐irradiated quartz crystals above 5 K

Parshin¹,

Laermans

2004

phys. stat. sol. (c)

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A linear temperature dependence of the sound velocity above 5 K is a universal property for amorphous and disordered solids. However, there are several theoretical models, which propose the explaination of this universal behaviour at intermediate temperatures. Previous low-temperature measurements have shown that the neutron-irradiated quartz can be used for the study of the glassy dynamics. In this paper we present the results of the ultrasound velocity measurements in neutron-irradiated quartz crystals at temperatures 5 -35 K and discuss them in the framework of the different models.Introduction Thermal and acoustical properties of amorphous solids below 1 K are well described in the framework of the tunnelling model [1,2,3]. Sound velocity of amorphous solids first increases logarithmically with temperature, reaches the maximum, and than decreases also logarithmically. This temperature dependence is described by equations: (∆v/v) res,TLS = C ln(T /T 0 ) and (∆v/v) rel,TLS = −

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

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Ultrasound velocity in neutron‐irradiated quartz crystals above 5 K

Parshin¹,

Laermans

2004

phys. stat. sol. (c)

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“…The fact that the influence of heat treatment seems to become important when the temperature approaches the ␣-␤ transition is interesting in view of the microscopic origin of the TS. In a recent paper, 8 we gave evidence that at least part of the TS is related to radiation induced ␣ 1 -␣ 2 twins. These twins consist of regions of SiO 4 tetrahedra which are 180°rotated with respect to each other and were proposed by Comes, Lambert, and Guinier 17 to explain the damaged ''crystalline'' structure of neutronirradiated quartz.…”

Section: The Influence Of Heat Treatments At 300 To 700°cmentioning

confidence: 98%

“…7 In order to obtain more information about the origin of these ''crystalline'' TS, we carried out recently ultrasonic measurements in neutron-irradiated z-cut quartz ͑whereas all previous measurements involved only x-cut specimens͒. 8 This study revealed a remarkable anisotropy in the behavior of the TS, which has to be attributed to the tunneling mechanism itself. These results gave evidence for the ␣ 1 -␣ 2 Dauphiné twins as microscopic origin of the ''crystalline'' TS, leading to a description of the tunneling mechanism as a rotation of coupled SiO 4 tetrahedra.…”

Section: Introductionmentioning

confidence: 99%

Influence of heat treatment on the tunneling states in neutron-irradiated quartz

Keppens

Laermans

1996

Phys. Rev. B

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We report the results of a systematic study of the influence of heat treatment on the tunneling states ͑TS͒ in neutron-irradiated quartz. Measurements of the ultrasonic attenuation and velocity change are carried out before and after heat treatment, as a function of temperature ͑0.3-300 K͒ and in the ultrasonic frequency range ͑50-650 MHz͒, on well-characterized specimens. Two doses have been studied, irradiated, and heat treated under similar conditions. One dose is lying well below the so-called threshold dose, the other is situated near the threshold. From numerical fits of the data with the tunneling model, the density of states P and the coupling parameter ␥ l were determined independently. This allows us to investigate the influence of the heat treatments on the number and nature of the TS. Attention is paid to both the influence of the annealing temperature and the length of the heat treatment. All samples still show the typical TS behavior after heat treatment, but the density of states is drastically reduced. Regarding the coupling, the two doses show a different behavior: while there is no influence on the coupling for the higher dose, a significant decrease in ␥ l is observed for the lowest dose. This decrease can be interpreted in terms of changes in the tunneling entity itself and is in agreement with the changes in the distribution of the TS.

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Tunneling Systems in Amorphous and Crystalline Solids

Esquinazi¹

1998

126

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Origin of the tunneling states inSiO2

Cited by 29 publications

References 16 publications

Ultrasound velocity in neutron‐irradiated quartz crystals above 5 K

Ultrasound velocity in neutron‐irradiated quartz crystals above 5 K

Influence of heat treatment on the tunneling states in neutron-irradiated quartz

Tunneling Systems in Amorphous and Crystalline Solids

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