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Register a new userSingle Crystal Growth, Transport, and Electronic Band Structure of YCoGa$_5$
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Single crystal of YCoGa5 has been grown via Ga self-flux. In this paper, we report the single crystal growth, crystallographic parameters, resistivity, heat capacity, and band structure results of YCoGa5. YCoGa5 accommodates the HoCoGa5 type structure (space group P4/mmm (No. 123), Z = 1, a = 4.2131(6) A, c = 6.7929(13) A, which is isostructural to the extensively studied heavy fermion superconductor system CeMIn5 (M = Co, Rh, Ir) and the unconventional superconductor PuCoGa5 with Tc = 18.5 K. No superconductivity is observed down to 1.75 K. Band structure calculation results show that its band at the Fermi level is mainly composed of Co-3d and Ga-4p electrons states, which explains its similarity of physical properties to YbCoGa5 and LuCoGa5.
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In this letter, we report growth and characterization of bulk Bi2Se3 single crystals. The studied Bi2Se3 crystals are grown by self flux method through solid state reaction from high temperature (950C) melt of constituent elements and slow cooling (2C/hour). The resultant crystals are shiny and grown in [00l] direction, as evidenced from surface XRD. Detailed Reitveld analysis of PXRD (powder x-ray diffraction) of the crystals showed that these are crystallized in rhombohedral crystal structure with space group of R3m (D5) and the lattice parameters are a = 4.14(2)A, b = 4.14 (2) A and c = 28.7010(7) A. Temperature versus resistivity (R-T) plots revealed metallic conduction down to 2K, with typical room temperature resistivity (R300K) of around 0.53 mohm-cm and residual resistivity of 0.12 mohm-cm. Resistivity under magnetic field ] measurements exhibited large +Ve magneto resistance right from 2K to 200K. Isothermal magneto resistance [RH] measurements at 2K, 100K and 200K exhibited magneto resistance (MR) of up to 240, 130 and 60 percent respectively at 14 Tesla. Further the MR plots are non saturating and linear with field at all temperature. At 2K the MR plots showed clear quantum oscillations at above say 10 Tesla applied field. Also the Kohler plots i.e., were seen consolidating on one plot. Interestingly, the studied Bi2Se3 single crystal exhibited the Shubnikov-de Haas oscillations (SdH) at 2K under different applied magnetic fields ranging from 4Tesla to 14 Tesla
We report a corrected crystal structure for the CePt2In7 superconductor, refined from single crystal x-ray diffraction data. The corrected crystal structure shows a different Pt-In stacking along the c-direction in this layered material than was previously reported. In addition, all the atomic sites are fully occupied with no evidence of atom site mixing, resolving a discrepancy between the observed high resistivity ratio of the material and the atomic disorder present in the previous structural model The Ce-Pt distance and coordination is typical of that seen in all other reported Ce_nM_mIn_3n+2m compounds. Our band structure calculations based on the correct structure reveal three bands at the Fermi level that are more three dimensional than those previously proposed, and Density functional theory (DFT) calculations show that the new structure has a significantly lower energy.
Orthorhombic (space group: Pnma) Nb2P5 is a high-pressure phase that is quenchable to ambient pressure, which could viewed as the zigzag infinite P chain-inserted NbP2. We report herein the high-pressure crystal growth of Nb2P5 and the discovery of its superconducting transition at Tc ~ 2.6 K. The electrical resistivity, magnetization, and specific heat capacity measurements on the high-quality crystal unveiled a conventional type-II weakly coupled s-wave nature of the superconductivity, with the upper critical field Hc2(0) ~ 0.5 T, the electron-phonon coupling strength {lambda}ep ~ 0.5 - 0.8, and the Ginzburg-Landau parameter k{appa} ~ 100. The ab initio calculations on the electronic band structure unveiled nodal-line structures protected by different symmetries. The one caused by band inversion, for example, on the {Gamma}-X and U-R paths of the Brillouin zone, likely could bring nontrivial topology and hence possible nontrivial surface state on the surface. The surface states on the (100), (010) and (110) surfaces were also calculated and discussed. The discovery of the phosphorus-rich Nb2P5 superconductor would be instructive for the design of more metal phosphides superconductors which might host unconventional superconductivity or potential technical applications.
Superconductivity was discovered in a Ni0:05TaS2 single crystal. A Ni0:05TaS2 single crystal was successfully grown via the NaCl/KCl flux method. The obtained lattice constant c of Ni0:05TaS2 is 1.1999 nm, which is significantly smaller than that of 2H-TaS2 (1.208 nm). Electrical resistivity and magnetization measurements reveal that the superconductivity transition temperature of Ni0:05TaS2 is enhanced from 0.8 K (2H-TaS2) to 3.9 K. The charge-density-wave transition of the matrix compound 2H-TaS2 is suppressed in Ni0:05TaS2. The success of Ni0:05TaS2 single crystal growth via a NaCl/KCl flux demonstrates that NaCl/KCl flux method will be a feasible method for single crystal growth of the layered transition metal dichalcogenides.
Recent experiments showed the distinct observations on the transition metal ditelluride NiTe$_2$ under pressure: one reported a superconducting phase transition at 12 GPa, whereas another observed a sign reversal of Hall resistivity at 16 GPa without the appearance of superconductivity. To clarify the controversial experimental phenomena, we have carried out first-principles electronic structure calculations on the compressed NiTe$_2$ with structure searching and optimization. Our calculations show that the pressure can transform NiTe$_2$ from a layered P-3m1 phase to a cubic Pa-3 phase at $sim$10 GPa. Meanwhile, both the P-3m1 and Pa-3 phases possess nontrivial topological properties. The calculated superconducting $T_c$s for these two phases based on the electron-phonon coupling theory both approach 0 K. Further magnetic transport calculations reveal that the sign of Hall resistance for the Pa-3 phase is sensitive to the pressure and the charge doping, in contrast to the case of the P-3m1 phase. Our theoretical predictions on the compressed NiTe$_2$ wait for careful experimental examinations.
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