Pressure induced Superconductivity and location of Fermi energy at Dirac point in BiSbTe3 (original) (raw)
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Pressure-induced superconductivity in topological parent compound Bi 2 Te 3
Proceedings of the National Academy of Sciences, 2010
We report a successful observation of pressure-induced superconductivity in a topological compound Bi 2 Te 3 with T c of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the hole-type carrier in the pressure-induced superconducting Bi 2 Te 3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi 2 Te 3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor.
Pressure-induced multiple phase transformations of the BaBi3 superconductor
Physical Review B, 2018
Measurements of temperature-dependent resistance and magnetization under hydrostatic pressures up to 2.13 GPa are reported for single-crystalline, superconducting BaBi3. A temperaturepressure phase diagram is determined and the results suggest three different superconducting phases α, β, and γ in the studied pressure range. We further show that occurrence of the three superconducting phases is intuitively linked to phase transitions at higher temperature which are likely first order and structural in nature. With the α phase being the ambient-pressure tetragonal structure (P 4/mmm), our first-principle calculations suggest the β phase to be cubic structure (P m − 3m) and the γ phase to be a distorted tetragonal structure where the Bi atoms are moved out of the face-centered position. Finally, an analysis of the evolution of the superconducting upper critical field with pressure further confirms these transitions in the superconducting state and suggests a possible change of band structure or a Lifshitz transition near 1.54 GPa in γ phase. Given the large atomic numbers of both Ba and Bi, our results establish BaBi3 as a good candidate for the study of the interplay of structure with superconductivity in the presence of strong spin-orbit coupling.
arXiv (Cornell University), 2019
We report a series of high-pressure electrical transport, magnetic susceptibility, and x-ray diffraction measurements on single crystals of the weak topological insulator Bi2TeI and the topological metal Bi3TeI. Room temperature x-ray diffraction measurements show that both materials go through a series of pressure-induced structural transitions and eventually adopt a disordered bcc alloy structure at high pressure. A re-analysis of the published data on BiTeI indicates that this material also adopts a disordered bcc structure at high pressure, in contrast to the previously suggested P 4/nmm structure. We find that Bi2TeI and Bi3TeI become superconducting at ∼13 GPa and ∼11.5 GPa, respectively. The superconducting critical temperature Tc of the bcc phase reaches maximum values of 7 K and 7.5 K for Bi2TeI and Bi3TeI, respectively and dTc/dP < 0 in both cases. The results indicate that disordered alloy bcc superconducting phases appear to be a universal feature of both the BiTe and BiTe -I systems at high pressure.
Pressure-induced superconductivity in the weak topological insulator BiSe
Physical Review B
Layered BiSe in the trigonal P3m1 phase is a weak topological insulator and a candidate topological crystalline insulator. Here using structural, spectroscopic, resistance measurements at high pressure and density functional theory calculations, we report that BiSe exhibits a rich phase diagram with the emergence of superconductivity above 7 GPa. Structural transitions into SnSe-type energetically tangled orthorhombic structures and, subsequently, into a CsCl-type cubic structure having distinct superconducting properties are identified at 8 and 13 GPa, respectively. Superconductivity is preserved as the system transforms back to the trigonal phase upon release of pressure. Spin-orbit coupling plays a significant role in enhancement of T c in the trigonal and cubic phases. In the orthorhombic Cmcm phase, T c decreases monotonically with increasing pressure, whereas unusual pressure-independent T c is observed in the cubic Pm3m phase. Theoretical analysis reveals topological surface states in the cubic phase. The emergence of superconductivity within the topological phases makes BiSe a candidate topological superconductor.
Possible superconductivity in the Bismuth IV solid phase under pressure
Scientific Reports, 2018
The first successful theory of superconductivity was the one proposed by Bardeen, Cooper and Schrieffer in 1957. This breakthrough fostered a remarkable growth of the field that propitiated progress and questionings, generating alternative theories to explain specific phenomena. For example, it has been argued that Bismuth, being a semimetal with a low number of carriers, does not comply with the basic hypotheses underlying BCS and therefore a different approach should be considered. Nevertheless, in 2016 based on BCS we put forth a prediction that Bi at ambient pressure becomes a superconductor at 1.3 mK. A year later an experimental group corroborated that in fact Bi is a superconductor with a transition temperature of 0.53 mK, a result that eluded previous work. So, since Bi is superconductive in almost all the different structures and phases, the question is why Bi-IV has been elusive and has not been found yet to superconduct? Here we present a study of the electronic and vibra...
Pressure-induced superconductivity and structural transitions in Ba(Fe0.9Ru0.1)2As2
The European Physical Journal B, 2014
High-pressure electrical resistance and x-ray diffraction measurements have been performed on ruthenium-doped Ba(Fe 0.9 Ru 0.1) 2 As 2 , up to pressures of 32 GPa and down to temperatures of 10 K, using designer diamond anvils under quasi-hydrostatic conditions. At 3.9 GPa, there is an evidence of pressure-induced superconductivity with T C onset of 24 K and zero resistance at T C zero 14.5 K. The superconducting transition temperature reaches maximum at ~ 5.5 GPa and decreases gradually with increase in pressure before completely disappearing above 11.5 GPa. Upon increasing pressure at 200 K, an isostructural phase transition from a tetragonal (I4/mmm) phase to a collapsed tetragonal phase is observed at 14 ± 1 GPa and the collapsed phase persists up to at least 30 GPa. The changes in the unit cell dimensions are highly anisotropic across the phase transition and are qualitatively similar to those observed in undoped BaFe 2 As 2 parent.
Pressure-induced superconductivity in BaFe 2 As 2 single crystal
EPL (Europhysics Letters), 2009
The evolution of pressure induced superconductivity in single crystal as well as polycrystalline samples of BaFe 2 As 2 has been investigated through temperature dependent electrical resistivity studies in 0-7 GPa pressure range. While the superconducting transition remains incomplete in polycrystalline sample, a clear pressure induced superconductivity with zero resistivity at the expense of magnetic transition, associated with spin density wave (SDW), is observed in the single crystal sample. The superconducting transition temperature (T C ) is seen to increase upto a moderate pressure of about ~1.5 GPa and decreases monotonically beyond this pressure. The SDW transition temperature T SDW decreases rapidly with increasing pressure and vanishes above ~1.5 GPa. PACS Number(s): 74.62.Fj, 74.70.Dd, 74.25.Fy * Corresponding author's email: mani@igcar.gov.in The recent discovery of superconductivity in the iron pnictides [1-3] has evoked immense response from scientific community which has culminated in synthesis of several new superconductors pertaining to these classes of compounds. Amazingly, in a limited span of time four homologous series of the Fe-pnictides, namely, 1111 (ROFeAs with R = rareearth; AeFFeAs with Ae = alkaline earth), 122 (AeFe 2 As 2 with Ae = Ba, Ca, Sr), 111 (AFeAs with A=Li, Na) and 011 (FeSe) have been discovered. Proper doping by electrons or holes in these parent compounds has resulted in the maximum superconducting transition temperatures (T C ) of ~ 55 K for 1111 [4], ~ 38 K for 122 [5, 6], and 12-25 K for 111 [7, 8], and ~ 9-14 K for 011 [9], respectively. One distinguishing feature of these pnictide superconductors is the existence of spin density wave (SDW) in the parent compounds, which gives way to superconductivity with electron or hole doping [4-9]. Apart from the ample future scope of enhancing the T C, as indicated in several doping studies, the occurrence of superconductivity in the presence of large concentration of the magnetic Fe in these layered compounds has provided an avenue to investigate the interplay of magnetism and superconductivity which may help in unraveling a long standing mystery of high temperature superconductivity. High pressure techniques provide valuable tools for altering and understanding of the electronic, structural and ground state properties of materials without introducing any chemical complexity. Several such studies carried out on above classes of FeAs -compounds have revealed the following general trends [10]: (1) Pressure tends to decrease the SDW transition temperature in the undoped or slightly doped compounds. (2) T C increases with
Superconductivity of barium-VI synthesized via compression at low temperatures
Physical Review B, 2017
Using a membrane-driven diamond anvil cell and both ac magnetic susceptibility and electrical resistivity measurements, we have characterized the superconducting phase diagram of elemental barium to pressures as high as 65 GPa. We have determined the superconducting properties of the recently discovered Ba-VI crystal structure, which can only be accessed via the application of pressure at low temperature. We find that Ba-VI exhibits a maximum T c near 8 K, which is substantially higher than the maximum T c found when pressure is applied at room temperature. We discuss our results in terms of the implications for pressure induced superconductivity in other elements exhibiting complex/modulated structures at high pressure. Finally, we highlight the potential of cryogenic compression to reveal additional richness in previously explored high pressure phase diagrams.