Bi2Te ICM presentation
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Transcript of Bi2Te ICM presentation
LLNL-PRES-674032
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC
Discovery of superconductivity in Bi2Te: Evidence
of universal behavior in an infinitely adaptive
series under compression
Ryan L. StillwellInternational Conference on Magnetism
Friday, July 10, 2015
Lawrence Livermore National Laboratory LLNL-PRES-6740322
Coauthors, collaborators and
contributors
Lawrence Livermore
National Laboratory
• Jason Jeffries
• Zsolt Jenei
• Scott McCall
• Sam Weir
• Dave Ruddle
University of Alabama
at Birmingham
Yogesh Vohra
National Institute of
Standards and Technology
Nicholas Butch
Lawrence Livermore National Laboratory LLNL-PRES-6740323
Turning topological insulators into
superconductors with high pressure: the (A2)m (A2Q3)n, A=Bi,Sb: Q=Se,Te series and related materials
Materials Pc (GPa) max. Tc (K) T.I.
Bi 7.6 8.4 No
Bi2Te3 11.9 9.4 Yes
Bi4Te3 16.2 8.4 Unconfirmed
Sb2Te3 30 7.3 Yes
Bi2Se3 30 7 Yes
Cux Bi2Se3 0 3.8 Yes
Lawrence Livermore National Laboratory LLNL-PRES-6740324
Infinitely adaptive (Bi2)m(Bi2Te3)n series
J.W.G. Bos et al., PRB, 75 (2007) 195203
Te
Bi
Lawrence Livermore National Laboratory LLNL-PRES-6740325
High temperature flux growth of
Bi2Te crystals
• High purity Bi and Te starting metals
• Grown using excess Bi as flux
• Alumina crucible
• Argon atmosphere
• 420oC soak, centrifuged at 318oC
• Confirmed structure with PXRD
Lawrence Livermore National Laboratory LLNL-PRES-6740326
Evidence of universal convergence to bcc phase at high pressure
O. Degtyareva et al., H.P.R. 24, 319 (2004)
M. Einaga et al., P.R.B 83, 092102 (2011)
J. Jeffries et al., P.R.B 84, 092205 (2011)
Lawrence Livermore National Laboratory LLNL-PRES-6740327
100 μm
Weir et al., APL, 77 (2000), 3400
Designer diamond anvil with diamond
encapsulated resistivity microprobes
• Steatite pressure medium
• Ruby fluorescence pressure calibration
• MP35N gasket
Sample at 2.6 GPa
ruby
steatite
Lawrence Livermore National Laboratory LLNL-PRES-6740328
Hall effect shows multiple carrier
changes as pressure is increased
T= 25K
Lawrence Livermore National Laboratory LLNL-PRES-6740329
Pressure induced metallization of
Bi2Te near 6 GPa
Lawrence Livermore National Laboratory LLNL-PRES-67403210
Onset of superconductivity at 11.5 GPa
with Tc max= 8.6 K at 14.5 GPa.
Lawrence Livermore National Laboratory LLNL-PRES-67403211
Sharp increase in Tc leads to
universal high pressure SC state
J.R. Jeffries et al., PRB, 84 092505 (2011)
Il’ina and Itskevitch, JETP Lett. 11, 218 (1970)
C. Zhang et al., PRB, 83, 140504(R) (2011)J. Jeffries et al., P.R.B 84, 092205 (2011)
C. Zhang et al., P.R.B 83, 140504(R) (2011)
M. Il’ina and E. Itskevich, JETP Lett. 11, 218 (1970)
Lawrence Livermore National Laboratory LLNL-PRES-67403212
Conclusions
Bi2Te XRD suggests universal high pressure convergence of
(Bi2)m(Bi2Te)n series into bcc phase from disparate ground states.
Bi2Te discovered to be a high pressure superconductor
Tc,onset(P=11.5 GPa) ~ 4K
Tc,max (P=14.5 GPa) = 8.6K
Bi2Te implies high pressure SC is universal in (Bi2)m(Bi2Te)n
Pressure is a good tool for exploring TI/SC physics.
Lawrence Livermore National Laboratory LLNL-PRES-67403214
Linear suppression of Tc by application
of magnetic field at 16.2 GPa
Lawrence Livermore National Laboratory LLNL-PRES-67403215
Hc has linear dependence over
accessible phase space