Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session B13: Focus Session: Topological Materials - Topological Superconductors and Half Heuslers |
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Sponsoring Units: DMP Chair: Jagadeesh Moodera, Massachusetts Institute of Technology Room: 315 |
Monday, March 18, 2013 11:15AM - 11:51AM |
B13.00001: Search for Topological Superconductivity in Superconducting Doped Topological Insulators Invited Speaker: Satoshi Sasaki Recent discovery of topological insulators (TIs) which can be characterized by topologically protected gapless surface states stimulated the search for an even more exotic state of matter, a topological superconductor (TSC), which is also predicted to have a topologically protected gapless surface state consisting of massless Majorana fermions as its distinctive characteristic. Low-carrier-density semiconductors with a strong spin-orbit coupling and a Fermi surface that is centered around time-reversal-invariant momenta, such as superconducting doped TIs, are predicted to be prime candidates for TSCs [1]. Following this prediction, we studied the nature of superconductivity in doped TIs, Cu$_x$Bi$_2$Se$_3$ and Sn$_{1-x}$In$_x$Te, by employing a conductance spectroscopy [2, 3]. I will present our latest results together with recent spectroscopy data from other groups, and summarize the current understanding of topological superconductivity in superconducting doped TIs. Work in collaboration with M. Kriener, Z. Ren, A. A. Taskin, K. Segawa, Y. Ando (Osaka Univ.), K. Yada, M. Sato, Y. Tanaka (Nagoya), and L. Fu (MIT). \\[4pt] \noindent [1] L. Fu and E. Berg, Phys. Rev. Lett. {\bf 105}, 097001 (2010). \\ \noindent [2] S. Sasaki, M. Kriener, K. Segawa, K. Yada, Y. Tanaka, M. Sato, and Y. Ando Phys. Rev. Lett. {\bf 107}, 217001 (2011). \\ \noindent [3] S. Sasaki, Z. Ren, A. A. Taskin, K. Segawa, L. Fu, and Y. Ando, arXiv:1208.0059 (2012). [Preview Abstract] |
Monday, March 18, 2013 11:51AM - 12:03PM |
B13.00002: Reversibility of Superconductivity in CuxBi2Se3 via Quenching Conditions John Schneeloch, Ruidan Zhong, Zhijun Xu, Alina Yang, Genda Gu, John Tranquada We investigated the effect of various growth and annealing conditions on Cu$_{0.3}$Bi$_{2}$Se$_{3}$, a compound proposed to host topological superconductivity. For annealing temperature $T > 580^{\circ}$C, quenching was found necessary for superconductivity, and the superconductivity loss due to not quenching after annealing was reversible by further annealing and quenching. For $T < 580^{\circ}$C, annealing was detrimental, even when followed by quenching. Floating zone growth and the annealing of thin ($< 1$ mm) crystals were found to be detrimental to superconductivity. [Preview Abstract] |
Monday, March 18, 2013 12:03PM - 12:15PM |
B13.00003: Crystal growth and physical property of Bi-Sb-Te-Se topological insulator materials, and Cu-Bi-Se and Sn-In-Te topological superconductors Genda Gu, Alina Yang, J. Schneeloch, R.D. Zhong, Z.J. Xu, J.M. Tranquada, Z.H. Pan, W.D. Si, X.Y. Shi, Q. Li, T. Valla The discovery of 3D topological insulator materials and topological superconductor opens up a new research field in the condensed matter physics. We have grown a number of Bi-Sb-Te-Se topological insulator, and Cu-Bi-Se and Sn-In-Te topological superconductor single crystals. We have measured the physical properties on these single crystals. We have studied the effect of growth condition and impurity on the bulk electrical conductivity of these single crystals. We try to answer two questions for the topological insulator materials if it is possible to grow the bulk-insulating topological insulator single crystals and Which maximum resistivity of these topological insulator single crystals we can grow. For the topological superconductor, we have got the bulk superconducting single crystals with a maximum Tc$=$4.5K. [Preview Abstract] |
Monday, March 18, 2013 12:15PM - 12:27PM |
B13.00004: Transport property of Cu-intercalated Bi$_2$Se$_3$ Atsutaka Maeda, Taiki Yoshinaka, Yoshinori Imai, Ryusuke Kondo Cu$_x$Bi$_2$Se$_3$($T_{\mathrm{c}} \sim 3.8$ K)[1] is a promising candidate material to be a topological superconductor, and it is very important to clarify the origin of its superconductivity. However, Cu$_x$Bi$_2$Se$_3$ synthesized by Hor \textit{et al.} does not show zero resistivity below $T_{\mathrm{c}}$ [1], and some concerns still remain in the quality of samples. Recently, several groups reported the successful preparation of Cu-intercalated Bi$_2$Se$_3$ with zero resistivity by an electrochemical method [2] and the Bridgman method [3]. Here, we report transport properties of single crystals of Cu$_x$Bi$_2$Se$_3$ with zero resistivity prepared by the Bridgman method. We stress that the process of the quenching from a temperature of about 1000 K into cold water is of crucial importance in the crystal growth process. The grown crystal with $x=0.10$ shows zero resistivity at about 3.2 K. We also report the results of the intercalations of different metal elements [4].\\[4pt] [1] Y.~S. Hor \textit{et al.}, PRL 104 (2010) 057001.\\[0pt] [2] M. Kriener \textit{et al.}, PRL 106 (2011) 127004.\\[0pt] [3] T. Kirzhner \textit{et al.}, arXiv:1111.5805. T. V. Bay \textit{et al.}, arXiv:1112.0102.\\[0pt] [4] Y. Imai \textit{et al.}, J. Phys. Soc. Jpn. 81 (2012) 113708. [Preview Abstract] |
Monday, March 18, 2013 12:27PM - 12:39PM |
B13.00005: Scanning Tunneling Microscopy Measurements of Superconductivity in Cu$_{\mathrm{x}}$Bi$_2$Se$_3$ Niv Levy, Tong Zhang, Jeonghoon Ha, Fred Sharifi, A. Alec Talin, Young Kuk, Joseph A. Stroscio The discovery of topological insulators has triggered the search for new topological states of matter. A Topological superconductor (TSC) is one such state, characterized by the existence of an unconventional superconducting gap in the bulk, and gapless Andreev bound states on the surface. Recently, Cu intercalated Bi$_{2}$Se$_{3}$ was found to be superconducting with T$_{\mathrm{C}}$ $\sim$ 3.8 K, and was considered a prime TSC candidate due to its band structure and strong spin-orbit coupling. A recent point contact measurement observed zero-bias conductance peaks, claiming these as evidence of surface Andreev bound states, and angle resolved photoemission spectroscopy has revealed the preservation of the topological surface states at the Fermi level. In this work we report scanning tunneling microscopy measurements of a cleaved Cu$_{0.2}$Bi$_{2}$Se$_{3}$ crystal. The measured tunneling spectrum is fully gapped and is well described by the classical s-wave BCS theory. In addition, spatially resolved measurements of the superconducting gap under an applied magnetic field found no bound states in the vortex cores. Both of these results suggest that Cu$_{0.2}$Bi$_{2}$Se$_{3}$ is a classical s-wave superconductor contrary to previous expectations and measurements. We will discuss current work examining the Cu concentration dependence. [Preview Abstract] |
Monday, March 18, 2013 12:39PM - 12:51PM |
B13.00006: Superconductivity in three dimensional topological compound via pressure C.Q. Jin, J. Zhu, J.L. Zhang, S.J. Zhang, X. Li, Q.Q. Liu, X. Dai, Z. Fang, W.G. Yang, G.Y. Shen, H.K. Mao Superconductivity in topological compounds is of great importance to the study of topological quantum phenomena. Here we report investigations of superconductivity induced via pressure in Bi$_{2}$Te$_{3}$ topological single crystals with various carrier types. We will discuss the possible relations of the superconductivity to topological scenario. [Preview Abstract] |
Monday, March 18, 2013 12:51PM - 1:03PM |
B13.00007: Effect of Indium on the Superconducting Transition Temperature of Tin Telluride Ruidan Zhong, John Schneeloch, Xiaoya Shi, Qiang Li, John Tranquada, Genda Gu Indium-doped tin telluride is one of the most appealing topological superconductors. We have grown a series of Sn$_{\mathrm{1-x}}$In$_{\mathrm{x}}$Te crystals with different indium concentrations (0.1$\le $x$\le $1.0). The results show indium doping improves the superconducting transition temperature significantly and is highly related to the indium concentration. The maximum Tc of indium-doped tin telluride polycrystalline is 4.5K for x$=$0.4. Single crystals of Sn$_{\mathrm{1-x}}$In$_{\mathrm{x}}$Te were also grown by the floating zone method, and their magnetic properties were characterized. [Preview Abstract] |
Monday, March 18, 2013 1:03PM - 1:15PM |
B13.00008: The Nature of the Superconductivity of Tl$_5$Te$_3$ Kathryn Arpino, David Wallace, Seyed Koohpayeh, Jiajia Wen, Katharine Page, Tingyong Chen, C.L. Chien, Tyrel McQueen The search for topologically non-trivial states of matter, such as topological insulators, has sparked significant interest in the impact of spin-orbit coupling on strongly correlated electronic behaviors, such as superconductivity. The known compound Tl$_5$Te$_3$ exhibits a superconducting transition at $T_c$ = 2.4 K, and contains heavy elements, making it an ideal compound in which to look for new physics at the intersection between superconductivity and strong spin-orbit coupling. In 1973, Haemmerle et al. conjectured that two-gap superconductivity might explain previous anomalous superconducting volume fractions observed in their polycrystalline samples. We have reinvestigated the superconductivity of Tl$_5$Te$_3$ using magnetic susceptibility, heat capacity, and point contact measurements on powder and single crystal samples, and resolved these previous discrepancies. Further, we report on long-range and local structure determination of superconducting and non-superconducting Tl$_5$Te$_3$ samples, as well as the relationship between structural details and the observed superconductivity. [Preview Abstract] |
Monday, March 18, 2013 1:15PM - 1:27PM |
B13.00009: Probing for Topological Superconductivity in In-doped SnTe Jeonghoon Ha, N. Levy, T. Zhang, H. Baek, D. Zhang, F. Sharifi, Y. Kuk, S. Sasaki, Z. Ren, A.A. Taskin, K. Segawa, Y. Ando, L. Fu, J.A. Stroscio Recent investigations of 3D topological insulators, which have gapless surface states protected by time reversal symmetry, have drawn attention to the search for new topological states protected by other symmetries. Theories predicted the existence of topological crystalline insulators (TCIs), which have gapless surface states protected by symmetry of the crystal lattice. In this work, we use scanning tunneling spectroscopy to investigate the superconducting properties of indium-doped tin telluride (Sn$_{\mathrm{1-x}}$In$_{\mathrm{x}}$Te), which is predicted to be a topological crystalline insulator. In a sample with T$_{\mathrm{c}}\approx $1.6 K, the tunneling spectra show a superconducting gap of 0.2 meV, which is continuous throughout the surface of the cleaved crystal. The superconducting gap is suppressed at a critical magnetic field of B$=$0.50 T and dI/dV conductance maps reveal a vortex lattice in a perpendicular applied magnetic field. Measurements will be shown as a function of In doping and discussed in relation to predictions and experiments on topological superconductivity in this material. [Preview Abstract] |
Monday, March 18, 2013 1:27PM - 1:39PM |
B13.00010: Transport and thermodynamic properties of topological semimetal candidate RPdBi (R:rare earth) Yasuyuki Nakajima, Rongwei Hu, Kevin Kirshenbaum, Alex Hughes, Paul Syers, Johnpierre Paglione The search for topologically non-trivial surface states, involving topologically protected gapless states on the boundary, is one of the central activities in the search for new quantum states of matter. Resent theoretical studies have indicated that the ternary half-Heusler system RPdBi (R:rare earth) can involve strong band inversion due to spin-orbit coupling, leading to the topologically non-trivial state. To clarify possible topological aspects of these materials, we report the characterization of single-crystal samples of RPdBi by transport and thermodynamic measurements down to very low temperatures. [Preview Abstract] |
Monday, March 18, 2013 1:39PM - 1:51PM |
B13.00011: Transport properties of the topological semi-metal LuPtBi under pressure Fazel Fallah Tafti, Takenori Fujii, Alxandre Juneau-Fecteau, Samuel Rene de Cotret, Nicolas Doiron-Leyraud, Atsushi Asamitsu, Louis Taillefer We present high-pressure magneto-transport data on single crystals of LuPtBi, a member of the ternary half-Heusler family. Recent band structure calculations show that LuPtBi is a topological semi-metal at ambient pressure due to strong spin-orbit coupling [1]. By decreasing the lattice parameter, equivalent to increasing pressure, the system should become a trivial insulator We have grown single crystals of LuPtBi and studied both the field dependence and the pressure dependence of their resistivity. The field dependence shows typical semi-metal behaviour, namely a weak temperature dependence and a large magneto-resistance. The pressure dependence shows a significant increase of resistivity and a decrease of magneto-resistance with increasing pressure. We compare our experimental results to the available theoretical work on the transport properties of topological semi-metals [2]. \\[4pt] [1] Stanislav Chadov, \textit{et al.} Nature, \textbf{9}, 541 (2010)\\[0pt] [2] W. Al-Sawai, et al. PRB, \textbf{82}, 125208 (2010) [Preview Abstract] |
Monday, March 18, 2013 1:51PM - 2:03PM |
B13.00012: Magnetism and physical properties of topological half-Heusler compounds RPdBi Rongwei Hu, Yasuyuki Nakajima, Kevin Kirshenbaum, Alex Hughes, Paul Syers, Johnpierre Paglione, Jeffrey Lynn The non-magnetic half-Heusler compounds, YPdBi and LuPdBi, have been proposed by band structure calculations to be candidates for three-dimensional topological insulators. We present magnetic susceptibility, neutron scattering and electrical transport measurements on single-crystal samples of a series of rare earth containing half-Heulser compounds RPdBi, showing that RPdBi are semimetals with dominant p-type carriers which exhibit antiferromagnetism associated with the rare earth local moments. [Preview Abstract] |
Monday, March 18, 2013 2:03PM - 2:15PM |
B13.00013: Low temperature specific heat of YBiPt Pascoal Pagliuso, Ryan Baumbach, Priscila Rosa, Cris Adriano, Joe Thompson, Zachary Fisk We present the specific heat measured on single crystals of the putative topological superconductor YBiPt between 0.35 and 20 K. The electronic specific coefficient per mole of compound is 0.3 mJ/ K$^{2}$. A break in slope of C/T vs T at T$_{c}$ = 0.7 K is seen, but no jump in C. We speculate on possible trace second phase in the crystals. [Preview Abstract] |
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