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Berret, Jean‐François; Meissner, M.; Watson, Susan K.; Pohl, Robert Wichard; Courtens, E.

doi:10.1103/physrevlett.67.93

Cited by 16 publications

(9 citation statements)

References 13 publications

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confidence: 93%

“…The disorder, combined with the ''frustration'' arising from the competition between FE ordering along the c axis in RDP and AFE ordering within the ab plane for ADP, leads to the characteristic broad and frequency-dependent peak in the dielectric susceptibility vs temperature T [1,2] and no more than short-range structural correlations [7]. The proton's pivotal role in relaxation is confirmed by the strong isotope effect on low T thermal properties [8].The dielectric spectroscopy is performed for 0:36 K T 300 K by the combined use of 3 He and helium-flow cryostats, with overlap of data sets for T 2:5-5 K. Detailed frequency f scans from 0.4 Hz to 2.5 MHz were taken at T 30 K, where the glassy behavior is manifest. Circular electrodes (5000 A gold=40 A Cr) with radii of 3-4 mm were evaporated concentrically on both sides of 1-mm thick ac-cut RADP:72 and RADP:35 single crystal plates, holding the temperature at the sample surface below 100 C to prevent decomposition during evaporation.…”

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confidence: 95%

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Quantum and Classical Relaxation in the Proton Glass

Feng¹,

Ancona-Torres²,

Rosenbaum³

et al. 2006

Phys. Rev. Lett.

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The hydrogen-bond network formed from a crystalline solution of ferroelectric RbH 2 PO 4 and antiferroelectric NH 4 H 2 PO 4 demonstrates glassy behavior, with proton tunneling the dominant mechanism for relaxation at low temperature. We characterize the dielectric response over seven decades of frequency and quantitatively fit the long-time relaxation by directly measuring the local potential energy landscape via neutron Compton scattering. The collective motion of protons rearranges the hydrogen bonds in the network. By analogy with vortex tunneling in superconductors, we relate the logarithmic decay of the polarization to the quantum-mechanical action. DOI: 10.1103/PhysRevLett.97.145501 PACS numbers: 61.43.Fs, 66.35.+a, 77.22.ÿd, 77.84.Fa Glasses become trapped in a restricted set of local configurations and evolve extraordinarily slowly over time. Delineating the relationship between the structure and the dynamics is a critical element in establishing the essential nature of the glassy state, but this correspondence remains difficult to access in most systems. The proton glass [1], a structural analogue to magnetic spin glasses [2] with competing ferroelectric (FE) and antiferroelectric (AFE) order, is different. By combining dielectric spectroscopy over seven decades in frequency with a direct mapping of the real-space energy potential via neutron Compton scattering [3], we are able to describe quantitatively the highly choreographed proton dynamics within a hydrogen-bond network. Proton tunneling controls correlations between neighboring hydrogen bonds and dominates the long-time relaxation.The hydrogen bond plays an important role in physics, chemistry, and biology [4], but it is probably most familiar from ice, where the freedom of different static configurations to accommodate Pauling's rule generates a macroscopic ground state and extra entropy contributing to the latent heat [5]. The hydrogen-bond network formed by Pauling's rule exists as well in other crystalline materials, for example, the piezoelectric KH 2 PO 4 (KDP) family [1,6]. Protons in four O-H-O bonds attached to each PO 4 3ÿ group are constrained to maintain singly charged H 2 PO 4 ÿ groups. Six distinct electrical dipole moments along three orthogonal axes can be formed with different Slater configurations [6]. While pure phases of RbH 2 PO 4 (RDP) and NH 4 H 2 PO 4 (ADP) are FE and AFE, respectively, at low temperature, a solid state solution creates a dipolar glass, Rb 1ÿx NH 4 x H 2 PO 4 (RADP:100x), for concentrations 0:22 < x < 0:74 [1]. The disorder, combined with the ''frustration'' arising from the competition between FE ordering along the c axis in RDP and AFE ordering within the ab plane for ADP, leads to the characteristic broad and frequency-dependent peak in the dielectric susceptibility vs temperature T [1,2] and no more than short-range structural correlations [7]. The proton's pivotal role in relaxation is confirmed by the strong isotope effect on low T thermal properties [8].The dielectric spectroscopy is performed f...

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confidence: 93%

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confidence: 95%

Quantum and Classical Relaxation in the Proton Glass

Feng¹,

Ancona-Torres²,

Rosenbaum³

et al. 2006

Phys. Rev. Lett.

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“…The above results show that the "two-level" states determining the low T properties of proton and deuteron glasses [4] are connected with intra H-bond motion. The O-H..O dipoles are not completely frozen even as T → 0 but show dynamic disorder characteristic of tunneling.…”

Section: Rb Spin-lattice Relaxationmentioning

confidence: 85%

“…In view of the fact that specific heat measurements [4] show the presence of dynamic disorder and possible tunneling at low temperatures, we decided to perform a site specific search for this motion. Deuteron intra H-bond motion seemed to be the most likely candidate for this kind of dynamic disorder.…”

Section: Deuteron Nmrmentioning

confidence: 99%

Low temperature properties of proton and deuteron glasses

Blinc

Dolinšsek

Zalar

1997

Zeitschrift für Physik B Condensed Matter

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“…Debye theory describes the low-temperature specific heat of ideal crystals, which may require isotopic purity [5][6][7] to show no deviations from T 3 behavior. At the other extreme, amorphous materials exhibit a larger and broader excess peak, suggesting a range of interactions between a distribution of energy quanta.…”

Section: Symbols Inmentioning

confidence: 99%

Modified Bose-Einstein and Fermi-Dirac statistics if excitations are localized on an intermediate length scale: Applications to non-Debye specific heat

Chamberlin

Davis

2013

Phys. Rev. E

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Disordered systems show deviations from the standard Debye theory of specific heat at low temperatures. These deviations are often attributed to two-level systems of uncertain origin. We find that a source of excess specific heat comes from correlations between quanta of energy if phonon-like excitations are localized on an intermediate length scale. We use simulations of a simplified Creutz model for a system of Ising-like spins coupled to a thermal bath of Einstein-like oscillators. One feature of this model is that energy is quantized in both the system and its bath, ensuring conservation of energy at every step. Another feature is that the exact entropies of both the system and its bath are known at every step, so that their temperatures can be determined independently. We find that there is a mismatch in canonical temperature between the system and its bath. In addition to the usual finite-size effects in the Bose-Einstein Experimental evidence for this model comes from its ability to characterize the excess specific heat of imperfect crystals at low temperatures.

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Glasslike thermal properties and isotope effect inRb1−x(NH

Cited by 16 publications

References 13 publications

Quantum and Classical Relaxation in the Proton Glass

Quantum and Classical Relaxation in the Proton Glass

Low temperature properties of proton and deuteron glasses

Modified Bose-Einstein and Fermi-Dirac statistics if excitations are localized on an intermediate length scale: Applications to non-Debye specific heat

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