Chapter 3: Thermal and Elastic Anomalies in Glasses at Low Temperatures

Hunklinger, Siegfried; Raychaudhuri, A. K.

doi:10.1016/s0079-6417(08)60015-3

Cited by 154 publications

(122 citation statements)

References 145 publications

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“…Applying the notion of the relaxational absorption to the two-level systems explained well the shape of the maximum in the temperature dependence of the sound speed at very low frequencies at ∼ 1K (Hunklinger and Raychaudhuri, 1986), which is one of the impressive achievements of the TLS model. In (Hunklinger and Raychaudhuri, 1986), the relation between the slopes of the logarithmic temperature profiles around the maximum was explained. At higher T , the logarithmic decrease in c s is followed by what has been viewed by others as a mysterious linear law (Belessa, 1978).…”

Section: G the Relaxational Absorptionmentioning

confidence: 68%

“…One important difference between the relaxational and resonant absorption is that the former does not saturate and can easily exceed the latter at low enough temperature and high enough sound intensity, which is what is usually observed in ultrasonic experiments unless special care is taken (Hunklinger and Raychaudhuri, 1986) (this saturation is not an issue in heat conductance, owing to the rather low sound intensities in these experiments). Applying the notion of the relaxational absorption to the two-level systems explained well the shape of the maximum in the temperature dependence of the sound speed at very low frequencies at ∼ 1K (Hunklinger and Raychaudhuri, 1986), which is one of the impressive achievements of the TLS model. In (Hunklinger and Raychaudhuri, 1986), the relation between the slopes of the logarithmic temperature profiles around the maximum was explained.…”

Section: G the Relaxational Absorptionmentioning

confidence: 87%

“…One point in favor of the STM is that it necessarily predicts time dependence of the specific heat. While a time dependence has been observed, its specific functional form has not been unambiguously established in the experiment (see (Hunklinger and Raychaudhuri, 1986;Pohl, 1981)). We also mention, for completeness, there is a different way to parametrize the two-level system motions within the more general, soft-potential model (Buchenau et al, 1992;Karpov et al, 1983).…”

Section: B the Universality Of Phonon Scatteringmentioning

confidence: 99%

“…The value c ∼ 0.1 implies the long time heat capacity should obey C ∝ T 1+α at low T , where α ∼ 0.05, a smaller number than observed in amorphous materials. We must bear in mind that the issue of the exact form of the time dependence in the laboratory still appears to be unresolved, as there is no definite agreement between different experiments; for references, see (Hunklinger and Raychaudhuri, 1986;Nittke et al, 1998;Pohl, 1981;Sahling et al, 2002). While there is no doubt that the specific heat is time-dependent, some experiments agree with the logarithmic time profile, as predicted by the STM, others give a lower or higher speed of variation with time.…”

Section: Distribution Of Barriers and The Time Dependence Of The Hmentioning

confidence: 99%

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The Microscopic Quantum Theory of Low Temperature Amorphous Solids

Lubchenko¹,

Wolynes²

2007

Advances in Chemical Physics

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The quantum excitations in glasses have long presented a set of puzzles for condensed matter physicists. A common view is that they are largely disordered analogs of elementary excitations in crystals, supplemented by two level systems which are chemically local entities coming from disorder. A radical revision of this picture argues that the excitations in low temperature glasses are deeply connected to the energy landscape of the glass when it vitrifies: the excitations are not low excited states built on a single ground state but locally defined resonances, high in the energy spectrum of a solid. According to a semiclassical analysis, the two level systems involve resonant collective tunneling motions of around two hundred molecular units which are relics of the mosaic of cooperative motions at the glass transition temperature Tg. The density of states of the TLS is determined by Tg and the mosaic's length scale, which is a weak function of the cooling rate. The universality of phonon scattering in insulating glasses is explained. The Boson Peak and the plateau in thermal conductivity, observed at higher temperatures, are also quantitatively understood within the picture as arising from the same cooperative motions, but now accompanied by thermal activation of the mosaic's vibrational modes. The dynamics of some of the local structural transitions have significant quantum corrections to the semiclassical picture. These corrections lead to a deviation of the heat capacity and conductivity from the standard tunneling model results and explain the anomalous time dependence of the heat capacity. Interaction between tunneling centers contributes to the large and negative value of the Grüneisen parameter often observed in glasses.

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Section: G the Relaxational Absorptionmentioning

confidence: 68%

Section: G the Relaxational Absorptionmentioning

confidence: 87%

Section: B the Universality Of Phonon Scatteringmentioning

confidence: 99%

Section: Distribution Of Barriers and The Time Dependence Of The Hmentioning

confidence: 99%

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The Microscopic Quantum Theory of Low Temperature Amorphous Solids

Lubchenko¹,

Wolynes²

2007

Advances in Chemical Physics

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“…The classic discovery by Zeller and Pohl [11] showed that excess specific heat of amorphous solids can be explained by the presence of two-level excitations. A phenomenological model based on tunneling two-level systems (TLS) has been able to model a variety of low-temperature mechanical and thermal properties of bulk solids and are not limited to modeling amorphous solids alone [12][13][14]. The standard TLS models assume that phenomenologically two-level excitations are present and probability of going to higher levels are negligible at low temperatures.…”

Section: Quantum Friction Due To Tunneling Two-level Systemsmentioning

confidence: 99%

Tunable low-temperature dissipation scenarios in palladium nanomechanical resonators

et al. 2017

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We study dissipation in palladium (Pd) nanomechanical resonators at low temperatures in the linear response regime. Metallic resonators have shown characteristic features of dissipation due to tunneling two-level systems (TLS). The system described here offers a unique tunability of the dissipation scenario by adsorbing hydrogen (H 2 ), which induces a compressive stress. The intrinsic stress is expected to alter TLS behavior. We find a sublinear ∼T 0.4 dependence of dissipation in a limited temperature regime. As seen in TLS dissipation scenarios, we find a logarithmic increase of frequency from the lowest temperatures till a characteristic temperature T co is reached. In samples without H 2 , T co ∼ 1 K was seen, whereas with H 2 it is clearly reduced to ∼700 mK. Based on standard TLS phenomena, we attribute this to enhanced phonon-TLS coupling in samples with compressive strain. We also find that with H 2 there is a saturation in low-temperature dissipation, which may possibly be due to super-radiant interaction between TLS and phonons. We discuss the data in the scope of TLS phenomena and similar data for other systems.

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Vibrational States In Disordered Solids

Pohl

2003

Digital Encyclopedia of Applied Physics

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Chapter 3: Thermal and Elastic Anomalies in Glasses at Low Temperatures

Cited by 154 publications

References 145 publications

The Microscopic Quantum Theory of Low Temperature Amorphous Solids

The Microscopic Quantum Theory of Low Temperature Amorphous Solids

Tunable low-temperature dissipation scenarios in palladium nanomechanical resonators

Vibrational States In Disordered Solids

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