Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session B35: Experimental Techniques and Results: Static High Pressure Physics |
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Sponsoring Units: DCMP DMP Room: 298 |
Monday, March 13, 2017 11:15AM - 11:27AM |
B35.00001: New Hydrides in the S-Se-P-H system synthesized at High Pressure- High Temperature conditions M. Ahart, A. K. Mishra, M. Somayazulu, C. Y. Park, Y. Meng, R. J. Hemley Although S-H system has been proved to be a remarkable high pressure superconductor with the observation of highest T$_{\mathrm{C\thinspace }}$\textasciitilde 203 K$_{\mathrm{\thinspace }}$by Drozdov et al, there is need to stabilize this family of hydrides at lower pressures and explore their superconducting properties. We have studied the analogous Se-H as well as the related solid solutions such as S:Se(50:50)-H, S:P(90:10)-H, S:P(10:90)-H system to realize new materials. In all these systems it has been possible to form hydrogen rich van der Waals compound (H$_{\mathrm{2}}$S)$_{\mathrm{2}}$H$_{\mathrm{2\thinspace }}$and its$_{\mathrm{\thinspace }}$analogs at pressures below 10 GPa and 800 K. Synthesis of these compounds are confirmed by XRD and Raman measurements. Some of them have been synthesized at higher pressures utilizing laser heating. We present details spectroscopic measurements as well as synchrotron x-ray diffraction measurements at ambient temperature as well as at low temperatures. [Preview Abstract] |
Monday, March 13, 2017 11:27AM - 11:39AM |
B35.00002: High pressure Fermi Surface measurements of the High Temperature Superconductor YBaCuO Stan Tozer, Audrey Grockowiak, William Coniglio, Louis Taillefer, Nicolas Dorion-Leyraud, Cyril Proust, Erik Kampert, Doug Bonn, Walter Hardy, Ruixing Liang Many quantum materials exhibit similar phase diagrams at low temperature, leading to a great deal of interest into a common mechanism for a ``universal phase diagram''. The typical ingredients of such phase diagrams include an antiferromagnetic phase, a superconducting dome, and possibly one, or several quantum critical points. Temperature versus chemical doping is one traditional way to look at such materials, however thermodynamic variables such as magnetic field or hydrostatic pressure have proved to be powerful tools to explore this phase diagram. Our group performed static high pressure SdH fermiology studies of YBCO at He-3 temperatures to fields of 70 T using an RF tank circuit based on a tunnel diode oscillator. [Preview Abstract] |
Monday, March 13, 2017 11:39AM - 11:51AM |
B35.00003: Superconductivity in the high pressure phases of barium D. E. Jackson, J. J. Hamlin At high pressure, barium goes through a series of structural phase transitions. Recently, low temperature x-ray diffraction measurements identified a a new structural phase at low temperatures (Ba-VI). Since Ba-VI appears to be accessible only via compression at low temperatures, the superconducting properties of Ba-VI are not well characterized. In this work, we used a bellows driven diamond anvil cell which allows us to load and unload pressure at low temperature to study the superconducting properties of Ba-VI. AC magnetic susceptibility measurements were used to measure the superconducting transition temperature and volume fraction in order to map out the superconducting properties of the stable and metastable phases of barium. [Preview Abstract] |
Monday, March 13, 2017 11:51AM - 12:03PM |
B35.00004: Time resolved x-ray diffraction: dynamics of pressure induced structural phase transition in bismuth. Zsolt Jenei, William J. Evans, Zuzana Konopkova, Hanns-Peter Liermann High brightness synchrotrons and fast high performance detectors allow direct measurement of structural phase transition in dynamic regime. We have used dynamic diamond anvil cell at 3$^{\mathrm{rd}}$ generation synchrotron facilities to study pressure induced phase transitions from slow to fast compression rates. Dynamic pressure changes can dramatically influence the microstructure of metals and phase boundaries in the pressure-temperature space. We explore the rich phase diagram of bismuth and discuss the effects of compression rate on solid-to-solid phase transition pressures in bismuth. [Preview Abstract] |
Monday, March 13, 2017 12:03PM - 12:15PM |
B35.00005: High pressure study on ZnCr2S4 spinel Yuejian Wang, Ilias Efthimiopoulos, Thomas Lochbiler, Vladimir Tsurkan, Alois Loidl We have performed structural and vibrational studies on the magnetically frustrated ZnCr2S4 spinel under high pressure up to 42 GPa. The starting materials crystallize in a cubic phase with space group \textit{Fd-3m}. Upon pressure increasing, two reversible structural transitions were observed at 22 GPa and 31 GPa, respectively. The first high-presure phase is identified as a tetragonal $I$41/\textit{amd} phase, whereas the second pressure-induced transition is attributed to an orthorhombic distortion of the tetragonal cell. We also detected the presence of a secondary (minority) high-pressure phase in those high pressure phases. Careful inspection of the starting \textit{Fd-3m} phase revealed a previously unnoticed isostructural transition, which is intimately connected with changes in the electronic properties. Finally, close comparison with the behavior of relevant Cr-bearing chalcogenide spinels revealed that the \textit{Fd-3m}$\to I$41/\textit{amd} transition pressure depends on the ratio of the magnetic exchange interactions active in these systems, i.e. it appears to originate from a spin-driven Jahn-Teller effect. [Preview Abstract] |
Monday, March 13, 2017 12:15PM - 12:27PM |
B35.00006: High-pressure structural study of Ammonium Perchlorate Elissaios Stavrou, Joseph Zaug, Sorin Bastea, Paulius Grivickas, Eran Greenberg, Martin Kunz Ammonium perchlorate (AP) with the chemical formula NH$_4$ClO$_4$ is a powerful energetic oxidizer used as an ingredient in rocket propellants and explosive formulations. For this reason, its structural properties under extreme conditions have attracted considerable attention (M. Dunuwille et al., S. Hunter et al.). However, its structural properties under pressure are not completely understood. In addition to its importance as an energetic oxidizer, AP is one of the simplest supramolecular systems. Thus, a structural study of AP under pressure can provide crucial information in the context of the emerging field of high pressure supramolecular chemistry. Ammonium perchlorate has been studied using x-ray diffraction and Raman spectroscopy up to the record pressure of 40 GPa. The results reveal a pressure-induced first order phase transition at $\sim$4 GPa, in agreement with previous studies. However, preliminary analysis of our results contradicts with the previously proposed high-pressure phase, as determined by neutron diffraction. No further structural phase transitions have been observed up to the highest pressure of this study. Intermolecular bonding between NH$_4$ and ClO$_4$ ions will be discussed based on Raman spectroscopy measurements. [Preview Abstract] |
Monday, March 13, 2017 12:27PM - 12:39PM |
B35.00007: Pressure-induced superconductivity in the giant Rashba system BiTeI Derrick VanGennep, Andreas Linscheid, Daniel Jackson, Sam Weir, Yogesh Vohra, Helmuth Berger, Greg Stewart, Richard Hennig, Peter Hershfeld, James Hamlin At ambient pressure, BiTeI is the first material found to exhibit a giant Rashba splitting of the bulk electronic bands. At low pressures, BiTeI undergoes a transition from trivial insulator to topological insulator. At still higher pressures, two structural transitions are known to occur. We have carried out a series of electrical resistivity and AC magnetic susceptibility measurements on BiTeI at pressure up to $\sim 40$~GPa in an effort to characterize the properties of the high-pressure phases. A previous calculation found that the high-pressure orthorhombic $P4/nmm$ structure BiTeI is a metal. We find that this structure is superconducting with $T_c$ values as high as 6~K. AC magnetic susceptibility measurements support the bulk nature of the superconductivity. Using electronic structure and phonon calculations, we compute $T_c$ and find that our data is consistent with phonon-mediated superconductivity. [Preview Abstract] |
Monday, March 13, 2017 12:39PM - 12:51PM |
B35.00008: Synthesis of Calcium polyhydrides at high pressure and high temperature Ajay Kumar Mishra, Muhtar Ahart, Maddury Somayazulu, C. Y. Park, Russel J. Hemley With the discovery of highest Tc, in H2S system by Drozdov et al. there is a renewed interest in synthesizing hydrogen rich materials as possible high Tc conventional superconductors. Recently there have been first principles predictions about alkaline and transition metal hydrides which are predicted to have higher T$_{\mathrm{C}}$. Hence, in order to synthesize higher hydrides of calcium we have loaded calcium metal and hydrogen in diamond anvil cell equipped with internal resistive heater. A new polyhydride of calcium, CaHx (x\textgreater 2) is synthesized at high pressure and high temperatures \textasciitilde 22 GPa and 500 deg C. It has been characterized and its structure is determined to be double hexagonal type. Compression behavior of this new hydride has been studied. On decompression it is unstable and decomposes into lower polyhydride of calcium. At higher pressures of \textasciitilde 121 GPa and 600 deg C, single crystal like new polyhydride CaHx with larger unit cell has been synthesized. We will present details of this newly synthesized superhydride as well as our attempts to characterize its superconducting properties. [Preview Abstract] |
Monday, March 13, 2017 12:51PM - 1:03PM |
B35.00009: Temperature dependence of alpha-epsilon phase transition in iron under high pressure Esen Alp, Wenli Bi, Jiyong Zhao, Michael Hu, Thomas Toellner, Stanislav Sinogeikin Temperature dependence of magnetic and structural phase transition in alpha-iron (bcc) under high pressure to epsilon iron (hcp) has been studied using nuclear resonant scattering of synchrotron radiation between 10-620 K. A detailed and precise phase boundary to determine the slope of dT/dP is determined. The experiments were conducted at the Advanced Photon Source during the hybrid fill mode, which provides unprecedented accuracy in determining the relative phase around the transition region. We will discuss possible mechanisms in light of extensive prior literature on the dependence of alpha-to-epsilon phase transition in iron under high pressure. [Preview Abstract] |
Monday, March 13, 2017 1:03PM - 1:15PM |
B35.00010: Phase diagram determination of $\alpha$-Uranium under pressure by single crystal x-ray diffraction William Coniglio, Audrey Grockowiak, Gaston Garbarino, Malcolm McMahon, Stan Tozer We grew single crystal $\alpha$-Uranium and studied its crystallographic properties at pressures up to 1.3 GPa using the ID-27 beam-line at the European Synchronon Radiation Facility. At low temperatures and pressures, we observed clear satellite peaks on the orthorhombic $\alpha$ structure, indicating one or more transitions into the charge-modulated phases. [Preview Abstract] |
Monday, March 13, 2017 1:15PM - 1:27PM |
B35.00011: Pressure and Temperature Dependent Raman Spectroscopy of Chalcogenide Perovskites Nelson Gross, Samanthe Perera, Xiucheng Wei, Yiyang Sun, Shengbai Zhang, Hao Zeng, B. A. Weinstein Inorganic semiconductors known as chalcogenide perovskites including BaZrS$_{3}$ and its alloys, show potential for application in photovoltaics. The phonon frequencies of BaZrS$_{3}$ have been investigated using Raman spectroscopy as a function of temperature from 14 K to 295 K at 1 atm, as well as a function of pressure up to 8.9 GPa at 295 K and up to 6.8 GPa at 120 K. In the range measured, pressure shifts of Raman peaks show no mode softening, indicating a robust and stable material in the Pnma space group. Due to this stability, BaZrS$_{3}$ serves as an excellent prototype for alloys occupying the same phase but having different unit cell volume. This volume change provides a method for band-gap tuning with the goal of more efficient energy harvesting. Results of these studies will be discussed. [Preview Abstract] |
Monday, March 13, 2017 1:27PM - 1:39PM |
B35.00012: Determination of melting curves of metals from resistance changes in the LHDAC Abhisek Basu, Reinhard Boehler A new method for determining melting temperatures of metals at high pressure is presented. The resistivity of laser-heated wires shows strong, discontinuous behavior both for solid-solid transitions and melting. In this technique we have used the split gasket method$^{\mathrm{1}}$, where the two gasket halves act as electrical leads for metal wires with dimensions 10 x 25 micron. Both alumina powder and KCl were used as pressure media. The wires were heated with an ytterbium fiber laser ($\lambda \quad =$ 1070 nm, TEM$_{\mathrm{00}}$ mode, CW, IPG-Photonics). Changes in the electrical resistance of the sample wire were measured by the two-terminal method using source meter (Keithley 2400) under a constant direct current of 100~mA. Iron was chosen as the test case for this new technique. Melting data up to 1 Mbar and 3200 K are reported showing a significant deviation from recently reported X-ray measurements$^{\mathrm{2}}$. Our new measurement for iron show melting temperature of iron consistent with previous findings of Boehler (1993)$^{\mathrm{3}}$ and Aquilanti \textit{et al}. (2015)$^{\mathrm{4}}$. References: 1) R. Boehler, Geophys. Res. Lett. \textbf{13}, 1153 (1986). 2) S. Anzellini \textit{et al.}, Science \textbf{340}, 464 (2013). 3) R. Boehler, Nature \textbf{363}, 534 (1993). 4) G. Aquilanti, PNAS \textbf{112}, 12042 (2015). [Preview Abstract] |
Monday, March 13, 2017 1:39PM - 1:51PM |
B35.00013: Extreme conditions magnetostriction study of the Shastry-Sutherland sample SCBO Audrey Grockowiak, Björn Wehinger, William Coniglio, Chistian Ruegg, Stanley Tozer The Shasty--Sutherland model, which consists of a set of spin 1/2 dimers on a 2D square lattice, is simple and soluble but captures a central theme of condensed matter physics by sitting precariously on the quantum edge between isolated, gapped excitations and collective, ordered ground states. This model is realized in SrCu2(BO3)2. Recent x-ray diffraction data revealed a direct correlation of the lattice with magnetic susceptibility measurements at low temperatures [1]. The variation of the lattice parameters with temperature is thus directly linked to the spin response of the system. Indeed, scattering intensities from the spin waves, measured by inelastic neutron scattering experiments, decay accordingly [2]. The magnetic correlations can thus be monitored by the lattice parameters and are thus sensitive to magnetostriction. Ambient pressure magnetostriction up to 100.7 T [5, 6] show clear signatures related to the magnetization plateaus at 30, 40 and 80T. Together with total energy calculations these studies revealed a strong magneto elastic coupling driven by the super exchange angle CuOCu. Applying hydrostatic external pressure results in continuous and discontinuous quantum phase transitions [1,3]. Zero field high pressure neutron spectroscopy measurements have revealed so far three phases : spin dimer from 0 to 2GPa, antiferromagnetic from 4 to 6 GPa, and a 4-spin plaquette singlet state was recently identified in the 2 to 4GPa region [4]. We report here on high pressure (up to 2GPa), high magnetic field (up to 65T) and 3He temperature magnetostriction experiments, using FBGs. Fiber Bragg Grating (FBG) Dilatometry [6] permits to measure the magnetostriction of a sample in function of the response of an optical fiber to applied strain. [1]Continuous and discontinuous quantum phase transitions in a model two-dimensional magnet Haravifarda S, et al., PNAS, Feb. 14, 2012 vol. 109 no. 7 2286--2289 [2] High-Resolution Study of Spin Excitations in the Singlet Ground State of SrCu2(BO3)2, B. Gaulin, et al., Phys.Rev. Lett. 93, 267202 (2004) [3]Quantum phase transitions in the orthogonal dimer system SrCu2.BO3.2 Hiroshi Kageyama H, et al. Physica B 329--333 (2003) 1020--1023 [4]Observation of a 4-spin Plaquette Singlet State in the Shastry--Sutherland compound SrCu2 (BO3 )2Zayed M.E., et al. arXiv: 1603.02039v [5]Magnetostriction and magnetic texture to 100.75 Tesla in frustrated SrCu2(BO3)2. Proc Natl Acad Jaime M, et al. Sci US109(31)12404--12407. (2012) [Preview Abstract] |
Monday, March 13, 2017 1:51PM - 2:03PM |
B35.00014: Noble metal electrodes encapsulated in diamond for laboratory tests of high-pressure, high-temperature superconductivity in hydrogen-rich materials Zachary Geballe, Kadek Hemawan, Russell Hemley Electrical transport measurements of hydrogen-rich materials at high-pressures (10s to 100s of GPa) are a promising route to experimentally test the many predictions of high-temperature superconductivity in polyhydrides. Major experimental challenges are to electrically isolate leads from the metal part of the gasket, to connect them to a precursor, and to trap hydrogen without shorting or breaking the electrical leads. To achieve all three goals, we combine sputtering of noble-metal electrodes (Pt or Ir) with spot-welding and low-pressure CVD growth of diamond films on the anvil culet. We will present our test results on the contact resistance between noble metal and metallic precursors, and on the hydrogen-trapping ability of these designer diamonds. [Preview Abstract] |
Monday, March 13, 2017 2:03PM - 2:15PM |
B35.00015: Studies of magnetism in dysprosium under extreme pressures Wenli Bi, Ercan Alp, Jing Song, Yuhang Deng, Jiyong Zhao, Michael Hu, Daniel Haskel, James S. Schilling The magnetism and valence of dysprosium have been investigated under high pressure up to 141 GPa using synchrotron M\"{o}ssbauer spectroscopy and x-ray absorption near edge structure (XANES). At ambient pressure Dy exhibits two types of magnetic ordering, antiferromagnetic ordering at 178 K followed by ferromagnetic ordering at 85 K. At 10 K the hyperfine magnetic field of Dy remains almost constant with increasing pressure to 141 GPa, showing the robustness of the magnetism, in contrast to Eu where pressure induces drastic changes in magnetism [1]. Above 1 Mbar the magnetic ordering temperature increases drastically with increasing pressure. At 141 GPa the magnetic ordering temperature is revealed to be higher than 230 K, in good agreement with previous electrical resistivity studies [2]. XANES experiments to 115 GPa find that Dy remains trivalent. [1]. W. Bi, J. Lim, G. Fabbris, J. Zhao, D. Haskel, E.E. Alp, M.Y. Hu, P. Chow, Y. Xiao, W. Xu, and J.S. Schilling, Phys. Rev. B 93, 184424 (2016). [2] J. Lim, G. Fabbris, D. Haskel, and J.S. Schilling, Phys. Rev. B 91, 45116 (2015). [Preview Abstract] |
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