Absence of Superconductivity in LK-99 at Ambient Conditions.

The report of the synthesis of modified lead apatite (LK-99), with evidence of superconductivity at more than boiling water temperature, has steered the scientific community. There have been several failures to reproduce superconductivity in LK-99, despite partial successes. Here, we have continued our efforts to synthesize phase-pure LK-99 with improved precursors.

Growth and characterization of the magnetic topological insulator candidate MnSbTe.

We report a new member of topological insulator (TI) family i.e. MnSbTe, which belongs to MnSbTefamily and is a sister compound of MnBiTe.

Probing the topological surface states in superconducting SnAu single crystal: a magneto transport study.

Materials exhibiting bulk superconductivity along with magnetoresistance (MR) in their normal state have emerged as suitable candidates for topological superconductivity. In this article, we report a flux free method to synthesize single crystal of topological superconductor candidate SnAu. The phase purity and single crystalline nature are confirmed through various characterizations viz.

Signature of weak-antilocalization in sputtered topological insulator BiSe thin films with varying thickness.

We report a low-temperature magneto transport study of BiSe thin films of different thicknesses (40, 80 and 160 nm), deposited on sapphire (0001) substrates, using radio frequency magnetron sputtering technique. The high-resolution x-ray diffraction measurements revealed the growth of rhombohedral c-axis {0003n} oriented BiSe films on sapphire (0001). Vibrational modes of BiSe thin films were obtained in the low wavenumber region using Raman spectroscopy.

Detailed magneto heat capacity analysis of SnAs topological superconductor.

In this article, we report magneto heat capacity analysis of superconducting SnAs. Magneto heat capacity analysis of superconductors is an important tool to determine bulk superconductivity as well as the pairing mechanism of Cooper pairs. SnAs crystal is characterized through x-ray diffraction and x-ray photoelectron spectroscopy.

Pressure Dependence of Superconducting Properties, Pinning Mechanism, and Crystal Structure of the FeMnSeTe Superconductor.

We have investigated the pressure () effect on structural (up to 10 GPa), transport [(): up to 10 GPa], and magnetic [((): up to 1 GPa)] properties and analyzed the flux pinning mechanism of the FeMnSeTe superconductor. The maximum superconducting transition temperature ( ) of 22 K with the coefficient of d /d = +2.6 K/GPa up to 3 GPa (d /d = -3.

Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies.

Proximity-induced superconducting energy gap in the surface states of topological insulators has been predicted to host the much wanted Majorana fermions for fault-tolerant quantum computation. Recent theoretically proposed architectures for topological quantum computation via Majoranas are based on large networks of Kitaev's one-dimensional quantum wires, which pose a huge experimental challenge in terms of scalability of the current single nanowire based devices. Here, we address this problem by realizing robust superconductivity in junctions of fabricated topological insulator (BiSe) nanowires proximity-coupled to conventional s-wave superconducting (W) electrodes.

Unexplored photoluminescence from bulk and mechanically exfoliated few layers of BiTe.

We report the exotic photoluminescence (PL) behaviour of 3D topological insulator BiTe single crystals grown by customized self-flux method and mechanically exfoliated few layers (18 ± 2 nm)/thin flakes obtained by standard scotch tape method from as grown BiTe crystals. The experimental PL studies on bulk single crystal and mechanically exfoliated few layers of BiTe evidenced a broad red emission in the visible region from 600-690 nm upon 375 nm excitation wavelength corresponding to optical band gap of 2 eV. These findings are in good agreement with our theoretical results obtained using the ab initio density functional theory framework.

Enhanced flux pinning in YBCO multilayer films with BCO nanodots and segmented BZO nanorods.

The flux pinning properties of the high temperature superconductor YBaCuO (YBCO) have been conventionally improved by creating both columnar and dot-like pinning centres into the YBCO matrix. To study the effects of differently doped multilayer structures on pinning, several samples consisting of a multiple number of individually BaZrO (BZO) and BaCeO (BCO) doped YBCO layers were fabricated. In the YBCO matrix, BZO forms columnar and BCO dot-like defects.

Superconducting gap structure in the electron doped BiS-based superconductor.

The influence of electron doping on semimetallic SrFBiS has been investigated by means of resistivity, zero and transverse  -  field (ZF/TF) muon spin relaxation/rotation (μSR) experiments. SrFBiS is semimetallic in its normal state and small amounts of La doping results in bulk superconductivity at 2.8 K, at ambient pressure.

Observation of quantum oscillations in FIB fabricated nanowires of topological insulator (BiSe).

In the last few years, research based on topological insulators (TIs) has been of great interest due to their intrinsic exotic fundamental properties and potential applications such as quantum computers or spintronics. The fabrication of TI nanodevices and the study of their transport properties has mostly focused on high quality crystalline nanowires or nanoribbons. Here, we report a robust approach to BiSe nanowire formation from deposited flakes using an ion beam milling method.

FIB synthesis of BiSe 1D nanowires demonstrating the co-existence of Shubnikov-de Haas oscillations and linear magnetoresistance.

Since the discovery of topological insulators (TIs), there are considerable interests in demonstrating metallic surface states (SS), their shielded robust nature to the backscattering and study their properties at nanoscale dimensions by fabricating nanodevices. Here we address an important scientific issue related to TI whether one can clearly demonstrate the robustness of topological surface states (TSS) to the presence of disorder that does not break any fundamental symmetry. The simple straightforward method of FIB milling was used to synthesize nanowires of BiSe which we believe is an interesting route to test robustness of TSS and the obtained results are new compared to many of the earlier papers on quantum transport in TI demonstrating the robustness of metallic SS to gallium (Ga) doping.

Unusual Dirac Fermions on the Surface of a Noncentrosymmetric α-BiPd Superconductor.

Combining multiple emergent correlated properties such as superconductivity and magnetism within the topological matrix can have exceptional consequences in garnering new and exotic physics. Here, we study the topological surface states from a noncentrosymmetric α-BiPd superconductor by employing angle-resolved photoemission spectroscopy and first-principles calculations. We observe that the Dirac surface states of this system have several interesting and unusual properties, compared to other topological surface states.

Dirty limit scattering behind the decreased anisotropy of doped YBa2Cu3O7-δ thin films.

We measured the resistivity of pulsed-laser-deposited BaCeO3 (BCO)-doped YBCO thin films containing spherical BCO particles in fields up to 30 T. The average diameter of the particles depends on the dopant concentration being below 4 nm in all the samples. Raised values of the upper critical field, Bc2, were observed in all the samples.

Ultrasensitive interplay between ferromagnetism and superconductivity in NbGd composite thin films.

A model binary hybrid system composed of a randomly distributed rare-earth ferromagnetic (Gd) part embedded in an s-wave superconducting (Nb) matrix is being manufactured to study the interplay between competing superconducting and ferromagnetic order parameters. The normal metallic to superconducting phase transition appears to be very sensitive to the magnetic counterpart and the modulation of the superconducing properties follow closely to the Abrikosov-Gor'kov (AG) theory of magnetic impurity induced pair breaking mechanism. A critical concentration of Gd is obtained for the studied NbGd based composite films (CFs) above which superconductivity disappears.

Effect of pressure on superconductivity in the indium-doped topological crystalline insulator SnTe.

We report on the impact of hydrostatic pressure on the superconductivity of optimally (indium)-doped SnTe which is established to be derived from a topological crystalline insulating phase. Single crystals of Sn(1-x)In(x)Te were synthesized by a modified Bridgman method that exhibited maximum superconducting Tc of 4.4 K for x = 0.

Photoemission studies of the near EF spectral weight shifts in FeSe1-xTex superconductor.

Our valence band photoelectron spectroscopic studies show a temperature dependent spectral weight transfer near the Fermi level in the Fe-based superconductor FeSe1-xTex. Using theoretical band structure calculations we have shown that the weight transfer is due to the temperature induced changes in the Fe(Se,Te)4 tetrahedra. These structural changes lead to shifts in the electron occupancy from the xz/yz and x2-y2 orbitals to the 3z2-r2 orbitals indicating a temperature induced crossover from a metallic state to an Orbital Selective Mott (OSM) Phase.

Local electromagnetic properties of magnetic pnictides: a comparative study probed by NMR measurements.

(75)As and (31)P NMR studies are performed in PrCoAsO and NdCoPO respectively. The Knight shift data in PrCoAsO indicate the presence of an antiferromagnetic interaction between the 4f moments along the c axis in the ferromagnetic state of Co 3d moments. We propose a possible spin structure in this system.

Bulk superconductivity in bismuth oxysulfide Bi4O4S3.

A very recent report on the observation of superconductivity in Bi(4)O(4)S(3) [Mizuguchi, Y.; http://arxiv.org/abs/1207.

Superconductivity of the bulk MgB(2)+nano(n)-SiC composite system: a high field magnetization study.

We study the effect of nano(n)-SiC addition on the crystal structure, critical temperature (T(c)), critical current density (J(c)) and flux pinning in MgB(2) superconductors. X-ray diffraction patterns show that all the samples have MgB(2) as the main phase with a very small amount of MgO; further, with n-SiC addition the presence of Mg(2)Si is also noted and confirmed by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The T(c) value for pure MgB(2) is 18.

Superconducting and magnetic behaviour of niobium doped RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-δ).

Polycrystalline samples of Ru(1-x)Nb(x)Sr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-δ), 0≤x≤0.

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212).

Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature.