Heat release and time-dependent thermal expansion of NbTi(D)

Escher, U.; Abens, S.; Gladun, A.; Köckert, C.; Sahling, S.; Schneider, M.

doi:10.1016/s0921-4526(99)02573-9

Cited by 2 publications

(6 citation statements)

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“…s . The wall mass estimate above, inspired by the Feynman's argument on the effective mass in liquid helium (Feynman, 1953), is entirely analogous to the well known estimate of the soliton mass in polyacetylene, see e.g. (Heeger et al, 1988).…”

Section: B the Multilevel Character Of The Entropic Droplet Excitationsmentioning

confidence: 55%

“…Finally, the renormalized valueǫ was used in the denominator. While, according to Feenberg's expansion (Feenberg, 1948), includingǫ in the resolvent is actually more accurate, we do it here mostly for convenience. Given that the semi-classical values of eigen-values ω i are known, the low energy portion of the energy level structure of the tunneling center, as shown in Fig.21, gives a quantitative idea of the eigen-energies of the full Hamiltonian only in the limit of a very small tunneling splitting ∆.…”

Section: Quantum Effects Beyond the Strict Semi-classical Picture mentioning

confidence: 99%

“…It may therefore take an excessively long time to actually observe the effects, discussed in this section, at very low temperatures, thus making it difficult to see a sign change in α for lattices with relatively large anharmonicity. Incidentally, this analysis predicts that the response of the length of an amorphous sample to a temperature change at sub-plateau temperatures must be time dependent (such time-dependence, acompanied by heat release, has been observed in polycrystalline NbTi (Escher et al, 2000)). Since the interaction effect is quadratic in concentration, one expects qualitatively that the relative rate of the expansion's time dependence should be twice that of the specific heat.…”

Section: Effect)mentioning

confidence: 99%

Section: G the Relaxational Absorptionmentioning

confidence: 99%

“…The barriers are therefore largely entropic. (It is nice to compare Feynman's discussion of the absence of energy barriers in superfluid He (Feynman, 1954) in this regard.) Below T A , such hopping already involves moving a number of molecules from one local minimum of the free energy functional to another such minimum and thus requires structural rearrangement within a certain cooperative length owing to the formation of metastable local arrangements.…”

Section: A Introduction: Classification Of Excitations In Glassesmentioning

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: B the Multilevel Character Of The Entropic Droplet Excitationsmentioning

confidence: 55%

Section: Quantum Effects Beyond the Strict Semi-classical Picture mentioning

confidence: 99%

Section: Effect)mentioning

confidence: 99%

Section: G the Relaxational Absorptionmentioning

confidence: 99%

Section: A Introduction: Classification Of Excitations In Glassesmentioning

confidence: 99%

See 3 more Smart Citations