Classical Glasses Research Articles

Dynamical mean-field theory of quantum stripe glasses

We present a many body approach for nonequilibrium behavior and self-generated glassiness in strongly correlated quantum systems. It combines the dynamical mean-field theory of equilibrium systems with the replica theory for classical glasses without quenched disorder. We apply this approach to study a quantized version of the Brazovskii model and find a self-generated quantum glass that remains in a quantum mechanically mixed state as $\stackrel{\ensuremath{\rightarrow}}{T}0.$ This quantum glass is formed by a large number of competing states spread over an energy region which is determined within our theory.

Slow non-equilibrium dynamics: parallels between classical and quantum glasses and gently driven systems

We review a scenario for the non-equilibrium dynamics of glassy systems that has been motivated by the exact solution of simple models. This approach allows one to set on firmer grounds well-known phenomenological theories. The old ideas of entropy crisis, fictive temperatures, free-volume … have clear definitions within these models. Aging effects in the glass phase are also captured. One of the salient features of the analytic solution, the breakdown of the fluctuation-dissipation relations, provides a definition of a bonafide effective temperature that is measurable by a thermometer, controls heat flows, partial equilibrations, and the reaction to the external injection of heat. The effective temperature is an extremely robust concept that appears in non-equilibrium systems in the limit of small entropy production as, for instance, sheared fluids, glasses at low temperatures when quantum fluctuations are relevant, tapped or vibrated granular matter, etc. The emerging scenario is one of partial equilibrations, in which glassy systems arrange their internal degrees of freedom so that the slow ones select their own effective temperatures. It has been proven to be consistent within any perturbative resummation scheme (mode coupling, etc) and it can be challenged by experimental and numerical tests, some of which it has already passed.

Non-equilibrium mode-coupling theory for supercooled liquids and glasses

A formally exact set of equations is derived for the description ofnon-equilibrium phenomena exhibited by classical liquids and glasses. Withthe help of a non-equilibrium projection operator formalism, thecorrelation functions and fluctuation propagators are expressed interms of memory functions and time-dependent collective frequencies.This formally exact set of equations is approximated by applyingmode-coupling approximations to the memory functions. The resultingset of equations for wave-vector-dependent correlation functions,fluctuation propagators and one-time structure factors Sq(t)generalizes the well known mode-coupling theory of the glasstransition to situations far away from equilibrium.

New oxysulphide glasses from the Sb 2O 3–Sb 2S 3·M xS system

New oxysulphide glasses involving Sb 2O 3, Sb 2S 3 and M x S(M=K, Na, Zn), which have different properties from classical oxide glasses and pure chalcogenides glasses, have been prepared. Glass-forming regions are given for the Sb 2O 3–Sb 2S 3, Sb 2O 3–MxS binary systems and ternary systems. These glasses are easy to prepare and chemically stable. The thermal and optical properties of the glasses have been measured and compared with Sb 2O 3 glass and Sb 2O 3–PbCl 2 glass. The oxysulphide glasses are transparent from 0.7 μm to 7.0 μm and T c, crystallization temperatures, T g, glass transition temperatures, Δ T( T c− T g) > 90°C.

Low-temperature specific heat of crystalline and amorphous Eu2(MoO4)3

The specific heat Ctotal of crystalline and amorphous Eu2(MoO4)3 is measured in the temperature interval 4.5–30 K. The amorphous state is obtained by applying pressure ∼7 GPa at room temperature. It is found that the specific heat of the crystal at T⩽7.5 K is described by a cubic function of temperature, while the specific heat of the amorphous sample has a strongly non-Debye character in the entire experimental temperature interval. The curve of Ctotal for amorphous europium molybdate is analyzed in a model of soft atomic potentials, and it is shown that it agrees well with universal low-temperature anomalies of the specific heat of classical glasses obtained by quenching from the liquid.

Quantum effects in the dynamics of proton glasses.

The dynamics of proton and deuteron glasses has been studied via the NMR spin-lattice relaxation (${T}_{1}$) of $^{87}\mathrm{Rb}$ and O-D\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}\ifmmode\cdot\else\textperiodcentered\fi{}O deuterons down to $T=1.6$ K in ${\mathrm{Rb}}_{0.50}$${(\mathrm{N}{\mathrm{H}}_{4})}_{0.50}$${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$, ${\mathrm{Rb}}_{0.58}$${(\mathrm{N}{\mathrm{D}}_{4})}_{0.42}$${\mathrm{D}}_{2}$P${\mathrm{O}}_{4}$, and ${\mathrm{Rb}}_{0.68}$${(\mathrm{N}{\mathrm{D}}_{4})}_{0.32}$${\mathrm{D}}_{2}$As${\mathrm{O}}_{4}$. In the glassy phase the relaxation rate was found to be anomalously short and temperature independent as $T\ensuremath{\rightarrow}0$, whereas this effect is absent in pure ferroelectric Rb${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$. The temperature independence of ${T}_{1}$ at low temperatures demonstrates the presence of phonon-assisted tunneling of the proton and the deuteron between the two potential minima in the H bond. The proton and deuteron glass phases are thus quantum rather than classical glasses.

Effect of Temperature Gradients on the Wave Aberration in Athermal Optical Glasses

Temperature gradients that are caused by partial heating in optical elements may result in wave aberrations. The athermal glasses developed within the past two years exhibit considerably reduced thermal wave aberrations compared to the classical optical glasses. Evidence is given that the total wave aberration is due not only to the change of optical path DeltaW(Gamma) computed from a, n, and dn/dT, but also that, upon the occurrence of thermal stresses, an additional wave aberration DeltaW(s) must be taken into consideration.

Use of plastics in the Fresnel rhomb.

IN this note the suitability of the new optical plastics for use in the Fresnel rhomb is discussed. Because the polarizing angle for a dielectric-to-air surface varies very little with change of frequency, and its polarizing properties are affected less by surface deterioration and the presence of films than is the case with metallic surfaces, polarization by internal reflexion remains the most satisfactory means of producing circularly polarized white light. The problem exists as to what is the most suitable non-metallic medium for this purpose. It is hoped that the following considerations will show that choice is not restricted to the classical glasses adopted since Fresnel's time.