Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session P58: Disordered and Glassy Systems II |
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Sponsoring Units: GSOFT Chair: Elijah Flenner, Colorado State Univ Room: BCEC 257A |
Wednesday, March 6, 2019 2:30PM - 2:42PM |
P58.00001: Measurement and modification of two-level tunneling states in amorphous aluminum oxide Thomas Metcalf, Xiao Liu, Matthew Abernathy, Battogtokh Jugdersuren Low energy excitations modeled as two-level tunneling systems (TLSs)—a significant source of decoherence in qubits built around superconducting Josephson junctions—are found nearly universally in amorphous dielectrics. Although TLS-free amorphous dielectric materials would be a technological boon, to date there is only one such material system: amorphous silicon thin films vapor deposited onto substrates held at elevated temperatures. The question arises whether TLSs can be eliminated in other, technologically pertinent amorphous dielectrics. To this end we have measured the internal friction of 100–300nm sputter-deposited aluminum oxide films, at substrate temperatures up to 500°C. This measurement directly yields the tunneling strength parameter from the TLS model, and we find a factor of five reduction in tunneling strength for films deposited at high temperatures. |
Wednesday, March 6, 2019 2:42PM - 2:54PM |
P58.00002: Entropy-dominated squeezout force and incipient glass formation in confined onic liquids Rosario Capozza, Erio Tosatti The squeezout force for an ionic liquid (IL) confined in a nanoscale channel between two approaching plates generally shows just short-range layering steps. Close to freezing temperature and at large squeezout speeds, recent data in a simple IL showed instead that short-range layering is replaced by a smooth intermediate range repulsive force tail. Along with the expected viscosity rise as in experiment, our squeezout simulations in a simple IL model additionally show that the confinement- induced strong and smooth repulsive squeezout force is of entropic origin, whereas the short-range layering steps are only controlled by internal energy. Our interpretation is guided by bulk glass-forming liquids, where the viscosity rise upon cooling is indeed associated with an entropy drop through the Adam-Gibbs mechanism, involving the formation of cooperatively rearranging regions (CRRs). We find that the confined IL the entropy drop and viscosity rise which accompany squeezout are also connected with remnants of a confinement-induced glassy CRRs forming at constant temperature, a mechanism that should be more general than this specific case. |
Wednesday, March 6, 2019 2:54PM - 3:06PM |
P58.00003: Topological phases, fragility- and reversibility-widows in GexPxSe100-2x ternary Aaron Welton, Ralph Chbeir, Soumendu Chakravarty, Punit Boolchand The fragility index, m, in homogenized chalcogenide melts, are found to display values of m < 20 for compositions that reside in the Intermediate Phase (IP) in the Ge-Se, Ge-S binary systems yielding a fragility window. The enthalpy of relaxation of corresponding glasses, ΔHnr(x) , becomes minuscule in IP displaying a reversibility window[1]. That correlation between ΔHnr(x) and m(x) illustrates a basic principle that melt dynamics encode glass topological phases. Here we examine the titled glasses to investigate if the principle extends to the present ternary. We have synthesized titled glasses over a wide range of compositions, 2% < x < 26% by alloying the pure elements in evacuated quartz tubes. Melts were alloyed till the variance in Ge stoichiometry x across the 2 gram batch composition nearly vanished using Raman profiling. In such homogenized glasses we are now examining the variation in ΔHnr(x) and m(x) using Modulated DSC , and will present the results of these observations. In a previous study[2] variation of ΔHnr(x) was examined but no attempt to measure the fragility index was made. |
Wednesday, March 6, 2019 3:06PM - 3:18PM |
P58.00004: The Energy Distribution of Two-Level Systems in Various Amorphous Thin Films Measured Using Internal Friction Matthew Abernathy, Xiao Liu, Thomas Metcalf, Battogtokh Jugdersuren Amorphous materials are known to universally possess various low-energy excitations generally modeled as two-level systems (TLS) capable of tunneling between states at low temperatures (~1K) and thermal excitation at higher temperatures (>5 K). The measurement and modeling of these states in bulk materials is well represented in the literature, however, relatively few measurements of amorphous thin films have been similarly analyzed. In this presentation, we fit the model of Rau et al. (Phys. Rev. B, 52, 7179, 1995) to the mechanical loss features attributed to TLS in thin films of a-Se, a-Al2O3, and others. |
Wednesday, March 6, 2019 3:18PM - 3:30PM |
P58.00005: Can you hear the shape of a crumpled sheet? Yoav Lahini, Shmuel Rubinstein, Ariel Amir Thin, crumpled sheets show surprisingly intricate dynamics: when subject to a constant load, they exhibit an extremely slow volume relaxation that spans many decades in time – from fractions of a second to weeks. After an abrupt change in the load, they show slow, non-monotonic aging and memory effects reminiscent of glassy systems. We have recently shown that these dynamics and scaling relations can be captured accurately using a phenomenological model in which the relaxation process is assumed to be governed by a linear superposition of many relaxation modes, that have a broad distribution of relaxation times. Here, we study, theoretically and experimentally, the statistics of discrete micro-mechanical relaxation events occurring within the system as it relaxes or exhibits memory. We find that during logarithmic relaxations the waiting time between these micro-mechanical ‘quakes’ displays approximate Poisson-statistics at any point in time, but with an average that grows linearly with the age of the system from preparation. The model is also used to predict the pattern of micro-relaxation events during the non-monotonic aging regime. The model predictions and experimental data of acoustic emission show god agreement. |
Wednesday, March 6, 2019 3:30PM - 3:42PM |
P58.00006: Critical size for dynamic crossover in amorphous nanoparticles Shan Zhang, Pengfei Guan, Lijin Wang The fragility, defined according to the non-Arrhenius degree of the viscosity-temperature dependence of a system in a supercooled state, is the essential, crucial, and universal dynamic attribute of the glass-forming liquid. It is related to the material-specific properties in liquid and glass state.1-2 We found that with the metallic glass nanoparticle's size reduced to critical size Rc, a fragile-to-strong transition appeared. This transition is the result of particle size reduction and the fast surface dynamic behavior. The analysis of morphology in PEL suggests that the strong liquids have the large fraction of low-energy excitations, reflecting the systems have a lower density of minima,3 fewer paths to translate into structural collapse. Meanwhile, this phenomenon is related to the atomic inherent structure energy and the two-body excess entropy in the surface. This fragile-to-strong transition is conducive to understand the micro-mechanism of the metallic glass at nano-scale further. |
Wednesday, March 6, 2019 3:42PM - 3:54PM |
P58.00007: Terahertz Time-Domain Spectroscopy of Alkali Borate Glass: Boson Peak Dynamics Tatsuya Mori, Yuta Iijima, Yasuhiro Fujii, Suguru Kitani, Jae-Hyon Ko, Akitoshi Koreeda, Hitoshi Kawaji, Seiji Kojima The boson peak (BP) is a universal feature of amorphous materials and it appears in the spectra of g(ν)/ν2 (g(ν): vibrational density of states), in the terahertz region. The BP can be famously detected by inelastic neutron scattering, low-temperature specific heat, and Raman scattering. Recently, we confirmed that terahertz time-domain spectroscopy (THz-TDS) is suitable to detect the BP. The BP in the infrared (IR) spectra appears in the spectrum of α(ν)/ν2 (α(ν): absorption coefficient). In this study, we investigate the BP dynamics of lithium borate glass by THz-TDS and evaluate IR light-vibration coupling coefficient. |
Wednesday, March 6, 2019 3:54PM - 4:06PM |
P58.00008: The relation between ridges and crumples Andrew Croll, Timothy Twohig, Theresa M Elder Crumpling is the name given to the structure created when a thin sheet has been forced to occupy a volume much smaller than the sheet’s largest dimension. Crumples strongly resist compression, making them an interesting lightweight material. How a crumple resists compression is a challenging question to answer, though recently we have proposed an empirical relation which applies to both elastic and plastic sheets. Here we examine different ‘building block’ structures for clues as to the origin of the empirical force law. Specifically, we focus on the stretching ridge which joins two developable-cones and has long been hypothesized to be responsible for the crumple’s strength. We show that elastic and plastic ridges, though geometrically identical when formed, behave very differently under compression. The elastic ridge smoothly collapses annihilating one d-cone in the process, whereas the plastic material allows no motion of the d-cone cores, building stress until buckling. Remarkably, before failure the plastic and elastic ridges can be fit by the same empirical model as can the crumple itself. We discuss the curious relationship. |
Wednesday, March 6, 2019 4:06PM - 4:18PM |
P58.00009: Evidence of a fragility window that correlates with the reversibility window in (Na2O)x (B2O3)100-x glasses Charles Skipper, Ralph Chbeir, Kandasamy Vignarooban, Punit Boolchand Evidence for a reversibility window in titled glasses was reported1 recently and permitted fixing the Topological phases. The reversibility window permitted one to identify glasses at x < 20% to be in the Stressed-rigid phase those at x > 40% to be in the flexible phase and those in between with the Intermediate Phase. We now report on melt fragility index using mDSC. The imaginary part of Cp, examined in the cool down mode, shows a Gaussian-like peak that shifts to higher T as the modulation frequency is increased. By tracking the peak shift in Cpimag with T, we establish how τ , the enthalpic relaxation time with T and deduce the fragility index (m). Our results show that m(x) also displays a square-well like variation with m< 20 in the 20 < x < 40% range of soda, coinciding with the reversibility window. Remarkably if the glasses are not dry the variation of m(x) changes qualitatively2; m(x) increases quadratically in x underscoring that Na+ ions now diffuse more rapidly. Glass synthesis conditions can qualitatively alter melt dynamics. |
Wednesday, March 6, 2019 4:18PM - 4:30PM |
P58.00010: Melt fragility index, configurational entropy, and topological phases in ternary GexAsxSe100-2x Chalcogenides Ralph Chbeir, Matthieu Micoulaut, Mathieu Bauchy, Punit Boolchand The melt fragility index, m, of titled chalcogenides display a global minimum with m < 20, in the narrow connectivity range 2.28(3) < <r> < 2.51(3) defining a fragility window. Separately, the non-reversing enthalpy of relaxation (ΔHnr) at Tg in corresponding glasses shows a square-well like global minimum, with the ΔHnr term nearly vanishing in the same 2.28(3) < <r> < 2.51(3) connectivity range, defining the reversibility window, which represents the isostatically rigid Intermediate Phase (IP). The near vanishing ΔHnr for IP glasses is signature for the change in excess configurational entropy (ΔSex) between melt and glass to be minuscule, and leads to super-strong melts as expected. The order of magnitude increases in ΔHnr for non-IP glass compositions as one goes away from the IP glass compositions, lead both ΔSex and m to steadily increase for non-IP melts as observed in experiments. |
Wednesday, March 6, 2019 4:30PM - 4:42PM |
P58.00011: Observation of a sharp reversibility window in rejuvenated homogenized equimolar GexAsxS100-2x bulk glasses Badriah Almutairi, Ralph Chbeir, Soumendu Chakravarty, L.C.R. Wijewardhana, Punit Boolchand
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Wednesday, March 6, 2019 4:42PM - 4:54PM |
P58.00012: Variation in fragility-index, Enthalpy of relaxation at Tg and Molar volumes in especially homogenized bulk AsxS100-x glasses Soumendu Chakravarty, Ralph Chbeir, Ping Chen, Matthieu Micoulaut, Mathieu Bauchy, Punit Boolchand, Badriah Almutairi We have measured the variation of fragility index (m), Non-reversing enthalpy of relaxation (ΔHnr) and molar volumes (Vm) with x in especially homogenized AsxS100-x batches of 1.5 gram in size. FT Raman profiling was used to ascertain homogeneity of glasses. Our results show that ΔHnr displays a square-well like minimum in the 22.5(5)% < x < 28.5(5)% range defining the reversibility window1. Variation of m displays a minimum of m < 20 in the same range of x, defining the fragility window. Inverse of the activation energy (Ea) for enthalpy relaxation shows a maximum in the IP. Variation in Vm(x) displays a Gaussian-like local minimum in the reversibility window. The fragility-window coinciding with the reversibility window underscores that super-strong (fragile) melts upon cooling give rise to IP (non-IP) glasses. The maximum in 1/Ea shows that the excess configurational entropy2 of melts (Sex) peaks for IP glasses, On the other hand, the large build up in ΔHnr and small increase in ΔCp for non-IP compositions (as x > 28.5(5)% and x < 22.5(5)%) as one goes away from the IP, accounts for the increased fragility of stressed-rigid and flexible melts. |
Wednesday, March 6, 2019 4:54PM - 5:06PM |
P58.00013: New scenario of sound damping in glasses Lijin Wang, Ludovic Berthier, Elijah Flenner, Pengfei Guan, Grzegorz Szamel An understanding of the difference between the universal low-temperature properties of amorphous solids and crystalline solids requires an explanation of the stronger damping of long-wavelength phonons in amorphous solids. A quartic scaling of the sound attenuation coefficient on the wavevector, which was deduced from experiments and later found support in a number of theoretical and simulation investigations, has recently been questioned in a new large scale simulation. Subsequently, quartic scaling was found in another large scale simulational study. These recent conflicting results reopened the problem of the wavevector dependence of sound attenuation. Here, we study simulated glasses with a wide range of stability and demonstrate the existence of a quartic scaling regime of the sound attenuation coefficient on wavevector in very stable glasses but not in poorly annealed glasses. For transverse sound waves in all glasses examined, we observe a long-wavelength quadratic scaling regime whose upper wavevector cutoff increases with increasing stability. Our results demonstrate an intimate connection between stability and sound damping in glasses and a new, unexpected damping scenario. |
Wednesday, March 6, 2019 5:06PM - 5:18PM |
P58.00014: Topological phases of (Na2O)x(P2O5)100-x glasses and their molecular structure from Raman scattering. Avik Mandal, Vamshi Gogi, Chandi Mohanty, Ralph Chbeir, Aaron Welton, Mathieu Bauchy, Matthieu Micoulaut, Punit Boolchand The observation of both a reversibility window and a fragility window in the 37.5% < x < 46% range of soda in titled glasses from Calorimetric experiments1 fixes the 3 topological phases. Raman polarization and glass compositional studies show that the feature near 1166 cm-1 in glasses at x = 50% consists of a triad of modes, a majority symmetric mode of Q2 species and two minority “defect modes” due to termination of the Q2 bearing long chains by Q1 like local structures, not only at x > 50% but also at x < 50%. These defects are under-constrained and contribute to an increasing baseline in the non-reversing heat flow term with increasing x. The fractions of Q3,Q2 and Q1 local structures with composition deduced from respective Raman active modes in the 20% < x < 60% range nicely track the usual mean-field behavior, independently deduced from NMR2 but with some minor but noticeable differences. |
Wednesday, March 6, 2019 5:18PM - 5:30PM |
P58.00015: Structure of (Na2O)x (P2O5)100-x glasses from Infrared reflectance measurements Vamshi Kiran Gogi, Avik Mandal, Chandi Mohanty, Mathieu Bauchy, Matthieu Micoulaut, Punit Boolchand IR reflectance has served as a useful complementary probe to Raman scattering on glasses. One observes a phonon near 1172.2 cm-1, associated with the long chains of Q2 species in Raman scattering of c-NaPO3. On the other hand, in g-NaPO3, the corresponding vibrational feature consists of a triad of modes1; a majority mode (1165.6 cm-1) and two minority ones (1151.4 cm-1 and 1105.3 cm-1). These minority modes are weakly excited in Raman but rather strongly in IR TO-response. The minority modes are ascribed to Q1 -like chain terminating topological defects of the long Q2 chains and display a global minimum in concentration in the IP composition range1 ; 37.5% < x < 46.0%. Additionally, when we examine the variation in the LO-TO splitting of the Q2asym (near 1282 cm-1) and Q3 asym (near 1316 cm-1) modes with glass composition ‘x’, one observes a global minimum in the IP range. A similar result is also observed for (Na2O)x (GeO2)100-x glasses2 , suggesting that the reduction of local Electric fields set up in the IP glassy networks could be a general feature. |
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