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Register a new userReinforcement of interfacial superconductivity in a Bi2Te3/Fe1+yTe heterostructure under hydrostatic pressure
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We investigate the hydrostatic pressure dependence of interfacial superconductivity occurring at the atomically sharp interface between two non-superconducting materials: the topological insulator (TI) Bi2Te3 and the parent compound Fe1+yTe of the chalcogenide iron based superconductors. Under pressure, a significant increase in the superconducting transition temperature Tc is observed. We trace the pressure dependence of a superconducting twin gap structure by Andreev reflection point contact spectroscopy (PCARS), which shows that a large superconducting gap associated with the interfacial superconductivity increases along with Tc. A second smaller gap, which is attributed to proximity-induced superconductivity in the TI layer, increases first, but then reaches a maximum and appears to be gradually suppressed at higher pressure. We interpret our data in the context of a pressure-induced doping effect of the interface, in which charge is transferred from the TI layer to the interface and the interfacial superconductivity is enhanced. This demonstrates the important role of the TI in the interfacial superconductivity mechanism.
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We report directional point-contact spectroscopy data on the novel Bi2Te3/Fe1+yTe interfacial superconductor for a Bi2Te3 thickness of 9 quintuple layers, bonded by van der Waals epitaxy to a Fe1+yTe film at an atomically sharp interface. Our data show a very large superconducting twin-gap structure with an energy scale exceeding that of bulk FeSe or FeSe1-xTex by a factor of 4. While the larger gap is isotropic and attributed to a thin FeTe layer in proximity of the interface, the smaller gap has a pronounced anisotropy and is associated with proximity-induced superconductivity in the topological insulator Bi2Te3. Zero resistance is lost above 8 K, but superconducting fluctuations are visible up to at least 12 K and the large gap is replaced by a pseudogap that persists up to 40 K. The spectra show a pronounced zero-bias conductance peak in the superconducting state, which may be a signature of an unconventional pairing mechanism.
The recent discovery of the interfacial superconductivity (SC) of the Bi2Te3/Fe1+yTe heterostructure has attracted extensive studies due to its potential as a novel platform for trapping and controlling Majorana fermions. Here we present studies of another topological insulator (TI)/Fe1+yTe heterostructure, Sb2Te3/Fe1+yTe, which also enjoys an interfacial two-dimensional SC. The results of transport measurements support that the reduction of excess Fe concentration of the Fe1+yTe layer not only increases the fluctuation of its antiferromagnetic (AFM) order but also enhances the quality of the SC of this heterostructure system. On the other hand, the interfacial SC of this heterostructure was found to have a wider-ranging TI-layer thickness dependence than that of the Bi2Te3/Fe1+yTe heterostructure, which is believed to be attributed to the much higher bulk conductivity of Sb2Te3 that enhances indirect coupling between its top and bottom topological surface states (TSSs). Our results provide the evidence of the interplay among the AFM order, itinerant carries from the TSSs and the induced interfacial SC of the TI/Fe1+yTe heterostructure system.
We report the effect of hydrostatic pressure (0-1.97GPa) on the superconductivity of BiS2 based CeO0.5F0.5BiS2 compound. The CeO0.5F0.5BiS2 superconductor was synthesized by the solid state reaction route and the compound is crystallized in tetragonal P4/nmm space group. The studied compound shows superconductivity with transition temperature of 2.5K (Tconset) at ambient pressure, which has been enhanced to 8 K at applied pressure of 1.97 GPa. The observed normal resistivity exhibited semiconducting behavior. The data of normal state resistivity R(T) has been fitted by activation type equation and it is found that the energy gap is significantly reduced with pressure. Resistivity measurements under magnetic field for the highest applied pressure of 1.97GPa (Tconset = 8K) exhibits the upper critical field of above 5Tesla. The observation of fourfold increase in Tc accompanied with improved normal state conduction under hydrostatic pressure on CeO0.5F0.5BiS2 superconductor calls for the attention of solid state physics community.
We have investigated the pressure effect on the newly discovered samarium doped La1-xSmxO0.5F0.5BiS2 superconductors. More than threefold increase in Tc (10.3 K) is observed with external pressure (at ~1.74 GPa at a rate of 4.08 K/GPa)) for x = 0.2 composition. There is a concomitant large improvement in the quality of the superconducting transition. Beyond this pressure Tc decreases monotonously at the rate of -2.09 K/GPa. In the x = 0.8 sample, we do not observe any enhancement in Tc with application of pressure (up to 1.76 GPa). The semiconducting behavior observed in the normal state resistivity of both of the samples is significantly subdued with the application of pressure which, if interpreted invoking thermal activation process, implies that the activation energy gap of the carriers is significantly reduced with pressure. We believe these observations should generate further interest in the La1-xSmxO0.5F0.5BiS2 superconductors.
We report the impact of hydrostatic pressure on the superconductivity and normal state resistivity of FeTe0.5Se0.5 superconductor. At the ambient pressure the FeTe0.5Se0.5 compound shows the superconducting transition temperature Tconset at above 13K and TcR=0 at 11.5K. We measure pressure dependent resistivity from 250K to 5K, which shows that the normal state resistivity increases initially for the applied pressures of up to 0.55GPa and then the same is decreased monotonically with increasing pressure of up to 1.97GPa. On the other hand the superconducting transition temperatures (Tconset and TcR=0) increase monotonically with increasing pressure. Namely the Tconset increases from 13K to 25K and TcR=0 from 11.5K to 20K for the pressures range of 0-1.97GPa. Our results suggest that superconductivity in this class of Fe-based compounds is very sensitive to pressure as the estimated pressure coefficient dTc(onset)/dP is 5.8K/GPa. It may be suggested that FeTe0.5Se0.5 superconductor is a strong electron correlated system. The enhancement of Tc with applying pressure is mainly attributed to an increase of charge carriers at Fermi surface.
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