Evidence for a Phase Transition in Glasses at Very Low Temperature: A Macroscopic Quantum State of Tunneling Systems?

Strehlow, Peter; Enss, C.; Hunklinger, Siegfried

doi:10.1103/physrevlett.80.5361

Cited by 82 publications

(96 citation statements)

References 14 publications

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“…A best fit to the 118 mK experimental data yields the parameters reported in Table II. The T -dependence of the calculated magnetocapacitance is also in qualitative agreement with the experimental data [3,4]. In a comparison with data for the BK7 and Duran glasses [4] (at the much lower only available temperature of 15.4 mK, however) the present theory reproduces the main features correctly.…”

supporting

confidence: 83%

Multiple-well tunneling model for the magnetic-field effect in ultracold glasses

Jug

2009

Phys. Rev. B

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Puzzling observations of both thermal and dielectric responses in multi-silicate glasses at low temperatures T to static magnetic fields B have been reported in the last decade and call for an extension of the standard two-level systems tunneling model. An explanation is proposed, capable of capturing at the same time the T -and B-dependence of the specific heat Cp and of the dielectric constant ǫ in these glasses. This theory points to the existence of anomalous multi-welled tunneling systems in the glasses -alongside the standard two-level systems -and indications are given for glasses which should achieve larger electric magnetocapacitive enhancements.PACS numbers: 61.43. Fs, 77.22.Ch, 65.60.+a The last decade has seen much renewed interest in the physics of cold non-metallic glasses, materials displaying some universal physical properties attributed to the lowenergy excitations characterising most amorphous solids. The two-level systems (2LS) tunneling model (TM) [1] has been rather successful in explaining a variety of interesting phenomena dealing with the thermal, dielectric and acoustic properties of structural glasses at temperatures T < 1 K. Limitations and failures of the 2LS TM (treating cooperative motion in terms of single particles, mostly) on the other hand, have been also discussed [2].These materials do not present, normally, any remarkable magnetic-field response phenomena other than possibly a weak contribution from trace paramagnetic Feimpurities. It came thus as a great surprise when measurements showed [3] that in some multi-component silicate glasses (but not in pure a-SiO 2 ) one is able to observe changes in the dielectric constant ǫ(T, B) and already in magnetic fields B as weak as a few Oe. A typical glass showing a strong response has some 100 ppm Fe 3+ and the composition Al 2 O 3 -BaO-SiO 2 (in short AlBaSi-O, in this paper). Measurements made on a thick sol-gel fabricated AlBaSi-O film showed changes in δǫ/ǫ = [ǫ(B) − ǫ(0)]/ǫ(0) of order 10 −4 and characterised by an enhancement peaking around 0.03 T for 10 mK < T < 200 mK then followed by a reduction of ǫ for B > 0.1 T. A further enhancement was also observed at much higher fields (B > 10 T).Another, cleaner, multi-component silicate glass (borosilicate BK7, with 6 ppm Fe 3+ ) and a dirtier one (borosilicate Duran, with 120 ppm Fe 3+ ) have shown similar -but weaker -magnetic anomalies, |δǫ/ǫ| ∼ 10 −5 , seemingly excluding the paramagnetic impurities as their source [4]. Yet another multi-silicate glass, aSiO 2+x C y H z was investigated [5], confirming the unusual findings in AlBaSi-O. A convincing explanation for the unusual electric magnetocapacitance behavior of these cold glasses has not yet been found.Recently, some consensus has been gained by the idea of a coupling of the standard 2LS to the magnetic field via nuclei in the glasses carrying an electric quadrupole moment as well as a magnetic dipole one [6]. The nuclear mechanism is supported by some features of the observed magnetic-field dependence of the polarization...

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supporting

confidence: 83%

Multiple-well tunneling model for the magnetic-field effect in ultracold glasses

Jug

2009

Phys. Rev. B

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“…Although theorists cleverly resolved the problem by pointing out the existence of two level tunneling systems (21), it has later surprised them to find universal characteristics of the density and scattering properties of these two level systems in a wide range of chemically distinct substances (22). Despite recent progress (23,24) no entirely convincing microscopic identification of what is actually tunneling has yet been made by experiment.…”

Section: Conflicts Of Principlementioning

confidence: 99%

The middle way

Laughlin

Pines

Schmalian

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

338

183

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Mesoscopic organization in soft, hard, and biological matter is examined in the context of our present understanding of the principles responsible for emergent organized behavior (crystallinity, ferromagnetism, superconductivity, etc.) at long wavelengths in very large aggregations of particles. Particular attention is paid to the possibility that as-yet-undiscovered organizing principles might be at work at the mesoscopic scale, intermediate between atomic and macroscopic dimensions, and the implications of their discovery for biology and the physical sciences. The search for the existence and universality of such rules, the proof or disproof of organizing principles appropriate to the mesoscopic domain, is called the middle way.

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“…In practice we calculate µ by first choosing an approximate value µ0 and calculating the corresponding value N (1) e . The correction δµ0 to µ0 can then be determined from…”

Section: Magnetic Field Dependence Of the Free Energymentioning

confidence: 99%

“…Ratios of δǫ ′ /ǫ ′ up to 10 −7 were achieved in that temperature regime. A rather spectacular success associated with that progress was the observation of a strong magnetic-field dependence of the polarizability of multicomponent glasses in the mK regime [1,2]. This development suggests reconsideration of magnetic field effects on ring molecules or related structures like nanotubes.…”

Section: Introductionmentioning

confidence: 99%

Dielectric response of cylindrical nanostructures in a magnetic field

Fulde

Овчинников

2000

Eur. Phys. J. B

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We study the magnetic field dependence of the dielectric response of large cylindrical molecules such as nanotubes. When a field-induced level crossing takes place, an applied electric field causes a linear instead of the usual quadratic Stark effect. This results in a large dielectric response. Explicit calculations are performed for doped nanotubes and a rich structure in the real part of the low-frequency dielectric function ǫ ′ (H) is found when a magnetic field is applied along the cylinder axis. It is suggested that studies of ǫ ′ (H, T ) can serve as a spectroscopic tool for the investigation of large ringshaped or cylindrical molecules. PACS

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Evidence for a Phase Transition in Glasses at Very Low Temperature: A Macroscopic Quantum State of Tunneling Systems?

Cited by 82 publications

References 14 publications

Multiple-well tunneling model for the magnetic-field effect in ultracold glasses

Multiple-well tunneling model for the magnetic-field effect in ultracold glasses

The middle way

Dielectric response of cylindrical nanostructures in a magnetic field

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