Publications (10)36.28 Total impact
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Article: Scaling of pressure-induced and doping-induced superconductivity in the Ca10(PtnAs8)(Fe2As2)5 arsenides
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ABSTRACT: The Ca10(PtnAs8)(Fe2As2)5 (n=3,4) compounds are a new type of iron pnictide superconductor whose structures consist of stacking Ca-PtnAs8-Ca-Fe2As2 layers in a unit cell. When n=3 (the 10-3-8 phase), the undoped compound is an antiferromagnetic (AFM) semiconductor, while, when n=4 (the 10-4-8 phase), the undoped compound is a superconductor (Tc=26K), a difference that has been attributed to the electronic character of the PtnAs8 intermediary layers. Here we report high-pressure studies on 10-3-8 and 10-4-8, using a combination of in-situ resistance, magnetic susceptibility, Hall coefficient and X-ray diffraction measurements. We find that the AFM order in undoped 10-3-8 is suppressed completely at 3.5 GPa and that superconductivity then appears in the 3.5-7 GPa pressure range with a classic dome-like behavior. In contrast, Tc in the 10-4-8 phase displays a monotonic decrease with increasing pressure. Our results allow for the establishment of a unique correspondence between pressure-induced and doping-induced superconductivity in the high-Tc iron pnictides, and also points the way to an effective strategy for finding new high-Tc superconductors.01/2013; -
Article: Pressure-induced insulator-metal transition and the pathway towards superconductivity in alkaline iron selenide compounds
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ABSTRACT: Here we show that a pressure of about 8 GPa suppresses both the vacancy order and the insulating phase, and a further increase of the pressure to about 18 GPa induces a second transition or crossover. No superconductivity has been found in compressed insulating 245 phase. The metallic phase in the intermediate pressure range has a distinct behavior in the transport property, which is also observed in the superconducting sample. We interpret this intermediate metal as an orbital selective Mott phase (OSMP). Our results suggest that the OSMP provides the physical pathway connecting the insulating and superconducting phases of these iron selenide materials.09/2012; -
Article: Re-emerging superconductivity at 48 kelvin in iron chalcogenides.
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ABSTRACT: Pressure has an essential role in the production and control of superconductivity in iron-based superconductors. Substitution of a large cation by a smaller rare-earth ion to simulate the pressure effect has raised the superconducting transition temperature T(c) to a record high of 55 K in these materials. In the same way as T(c) exhibits a bell-shaped curve of dependence on chemical doping, pressure-tuned T(c) typically drops monotonically after passing the optimal pressure. Here we report that in the superconducting iron chalcogenides, a second superconducting phase suddenly re-emerges above 11.5 GPa, after the T(c) drops from the first maximum of 32 K at 1 GPa. The T(c) of the re-emerging superconducting phase is considerably higher than the first maximum, reaching 48.0-48.7 K for Tl(0.6)Rb(0.4)Fe(1.67)Se(2), K(0.8)Fe(1.7)Se(2) and K(0.8)Fe(1.78)Se(2).Nature 03/2012; 483(7387):67-9. · 36.28 Impact Factor -
Article: Reemerging superconductivity at 48 K across quantum criticality in iron chalcogenides
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ABSTRACT: Pressure plays an essential role in the induction1 and control2,3 of superconductivity in iron-based superconductors. Substitution of a smaller rare-earth ion for the bigger one to simulate the pressure effects has surprisingly raised the superconducting transition temperature Tc to the record high 55 K in these materials4,5. However, Tc always goes down after passing through a maximum at some pressure and the superconductivity eventually tends to disappear at sufficiently high pressures1-3. Here we show that the superconductivity can reemerge with a much higher Tc after its destruction upon compression from the ambient-condition value of around 31 K in newly discovered iron chalcogenide superconductors. We find that in the second superconducting phase the maximum Tc is as high as 48.7 K for K0.8Fe1.70Se2 and 48 K for (Tl0.6Rb0.4)Fe1.67Se2, setting the new Tc record in chalcogenide superconductors. The presence of the second superconducting phase is proposed to be related to pressure-induced quantum criticality. Our findings point to the potential route to the further achievement of high-Tc superconductivity in iron-based and other superconductors.10/2011; -
Article: Correlation between superconductivity and antiferromagnetism in Rb0.8Fe2Se2-xTex single crystals
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ABSTRACT: We report the first experimental evidence for the intimate connection between superconductivity and antiferromagnetism in Rb0.8Fe2Se2-xTex single crystal under negative chemical pressure by substituting Se with isovalent Te atoms. Electrical resistance measurements in the temperature range from 4 K to 550 K demonstrate that both superconducting transition temperature (Tc) and Neel temperature (TN) were suppressed continuously with the lattice expansion. When the Te concentration x in Rb0.8Fe2Se2-xTex approaches 0.3, the superconducting transition temperature Tc is completely suppressed and the sample behaves like a semiconductor, meanwhile the characteristic peak of antiferromagnetic transition on resistance curve disappears. Our observation suggests that the pressure-induced lattice expansion can be used to tune the correlativity of superconductivity and antiferromagnetism.07/2011; -
Article: Pressure-Driven Quantum Criticality in An Iron-Selenide Superconductor
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ABSTRACT: The discovery of superconductivity of about 30 K in iron selenides with very large magnetic moments simulates the examination of completing orders. Here we report a finding of pressure- induced suppression of the superconducting transition temperature Tc and enhancement of the temperature of the resistance hump TH through charge transfer between two iron sites with different occupancies. The activation energy for the electric transport of the high-temperature resistance is observed to go to zero at a critical pressure of 8.7 GPa, at which superconductivity tends to disappear and the semiconductor-to-metal transition takes place. Beyond the critical point, the resistance exhibits a metallic behavior over the whole temperature range studied. All these features indicate the existence of quantum criticality in iron-selenide superconductors.12/2010; -
Article: Valence change of europium in EuFe_ {2} As_ {1.4} P_ {0.6} and compressed EuFe_ {2} As_ {2} and its relation to superconductivity
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ABSTRACT: Superconductivity can be realized in Eu-containing pnictides by applying chemical (internal) and physical (external) pressure, the intrinsic physical mechanism of which attracts much attention in the studies of pnictide superconductors. Here we present the experimental evidence for the pressure-induced valence change of europium in EuFe2As1.4P0.6 exposed to ambient pressure and EuFe2As2 to high pressure by x-ray absorption measurements on L3-Eu edge. We found that the absorption spectrum of EuFe2As1.4P0.6 showed a clear spectra weight transfer from divalent to trivalent state. Furthermore, a similar behavior of valence transition as in EuFe2As1.4P0.6 was also observed in EuFe2As2 when pressure was applied. This reports the observation of valence change in pnictide superconductors and the analysis of its influence on superconductivity in EuFe2As1.4P0.6 and compressed EuFe2As2.Phys. Rev. B. 10/2010; 82(13). -
Article: Phase Diagram of Pressure-induced Superconductivity and its Relation to Hall Coefficient in Bi2Te3 Single Crystal
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ABSTRACT: Pressure-induced superconductivity and its relation to corresponding Hall coefficient (RH) have been reported for Bi2Te3, one of known topological insulators. A full phase diagram is presented which shows a complex dependence of the superconducting transition temperature as a function of pressure over an extensive range. High-pressure RH measurements reveal a close relation of these complex behaviors, particularly, a dramatic change of dRH/dP before structural phase transition and a pressure-induced crossover on RH in the high pressure phase were observed.09/2010; -
Article: Pressure-induced Tc enhancement up to 48.3 K in EuFe2As1.4P0.6 single crystal
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ABSTRACT: Here we report comprehensive studies of pressure effect on superconducting transition temperature (Tc) in optimally doped EuFe2As1.4P0.6 single crystal. We found that the Tc of the sample compressed at ~9 GPa was enhanced up to 48.3K, which is far beyond the ultimate temperature (39K) of MacMillan's prediction and sets the highest record in MFe2As2 system (M=Ca, Sr, Ba and Eu) so far. Obviously different from the pressure dependence of Tc in optimally doped BaFe2As1.3P0.7, the experimental results demonstrated that the pressure dependence of Tc for the sample investigated exhibited nonmonotonic behavior, i.e. the Tc increased with pressure initially before reaching the maximum at ~9 GPa, then dramatically decreased with further increasing pressure and disappeared at ~21 GPa eventually. In-situ x-ray diffraction (XRD) and x-ray absorption measurements with diamond anvil cells revealed that the pressure-induced valence transition of Eu ions was a favorable factor for the Tc enhancement, while the formation of collapsed tetragonal phase was a negative factor for the superconducting transition.08/2010; -
Article: Physical origin of superconductivity in EuFe2As1.4P0.6 and EuFe2As2: pressure-induce valence change of europium
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ABSTRACT: Superconductivity can be realized in Eu-containing pnictides by application of chemical (internal) and physical (external) pressure, the intrinsic physical mechanism of which attracts much attention in physics community. Here we present the experimental evidence for the valence change of europium in compounds of EuFe2As1.4P0.6 exposed to ambient pressure and EuFe2As2 to high pressure by x-ray absorption measurements on L3-Eu edge. We find that the absorption spectrum of EuFe2As1.4P0.6 at ambient pressure shows clear spectra weight transfer from a divalent to a trivalent state. Furthermore, application of pressure on EuFe2As2 using a diamond anvil cell shows a similar behavior of valence transition as EuFe2As1.4P0.6. These findings are the first observation of superconductivity mechanized by valence change in pnictides superconductors and elucidate the intrinsic physical origin of superconductivity in EuFe2As1.4P0.6 and compressed EuFe2As2. Comment: 13 pages, 3 fifures05/2010;
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- Nature (1)
Institutions
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2010–2012
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Chinese Academy of Sciences
- Institute of Physics
Beijing, Beijing Shi, China
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