Related papers: Internal pressure in superconducting Cu intercalat…
The superconducting systems emerging from topological insulators upon metal ion intercalation or application of high pressure are ideal for investigation of possible topological superconductivity. In this context, Sr-intercalated…
Recent observations of two nodeless gaps in superconducting CeCu$_2$Si$_2$ have raised intensive debates on its exact gap symmetry, while a satisfactory theoretical basis is still lacking. Here we propose a phenomenological approach to…
The heating-compensated interlayer tunneling spectroscopy is performed on stacks of Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$ intrinsic junctions. The high-accuracy spectra without the local heating, for varying temperatures and magnetic fields, reveal…
When certain elemental metals like Cu, Sr and Nb are intercalated between the layers of Bi$_2$Se$_3$, a topological insulator, the intercalated systems superconduct with critical temperatures around 3 K. Naturally, in all these cases, the…
We have investigated the optimally doped tri-layer cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+\delta}$ (Bi2223) by angle-resolved photoemission spectroscopy, and observed energy bands and Fermi surfaces originated from the outer and inner…
A topological insulator Bi2Se3 which shows superconducting property due to Cu doping has been studied using high resolution transmission electron microscopy which provides for the first time, the direct evidence of intercalation sites. A…
We present muon spin rotation measurements on superconducting Cu intercalated Bi$_2$Se$_3$, which was suggested as a realization of a topological superconductor. We observe a clear evidence of the superconducting transition below 4 K, where…
We discuss polarization selection rules for angle-resolved photoemission spectroscopy in Bi2212. Using these we show that the ``hump'' in the superconducting gap observed in the $X$ quadrant in our earlier work is not on the main $CuO_2$…
We report on the structural and electronic properties of a single bismuth layer intercalated underneath a graphene layer grown on an Ir(111) single crystal. Scanning tunneling microscopy (STM) reveals a hexagonal surface structure and a…
The recently discovered topological insulators exhibit topologically protected metallic surface states which are interesting from the fundamental point of view and could be useful for various applications if an appropriate electronic gating…
The temperature dependence of the complex optical properties of the three-dimensional topological insulator Bi2Te2Se is reported for light polarized in the a-b planes at ambient pressure, as well as the effects of pressure at room…
The crystal structure of the candidate topological superconductor Cu$_x$Bi$_2$Se$_3$ was studied by single-crystal neutron diffraction using samples obtained by inserting the Cu dopant electrochemically. Neither structural refinements nor…
Proximity-effect-induced superconductivity was studied in epitaxial topological insulator Bi2Se3 thin films grown on superconducting NbSe2 single crystals. A point contact spectroscopy (PCS) method was used at low temperatures down to 40…
Topological insulators are bulk semiconductors that manifest in-gap massless Dirac surface states due to the topological bulk-boundary correspondence principle [1-3]. These surface states have been a subject of tremendous ongoing interest,…
In high temperature cuprate superconductors, the interlayer coupling between the CuO$_2$ planes plays an important role in dictating superconductivity, as indicated by the sensitive dependence of the critical temperature (T$_C$) on the…
We have investigated the optical properties of thin films of topological insulators Bi$_{2}$Te$_{3}$, Bi$_{2}$Se$_{3}$ and their alloys Bi$_2$(Te$_{1-x}$Se$_x$)$_3$ on BaF$_{2}$ substrates by a combination of infrared ellipsometry and…
Metal intercalation into layered topological insulator materials such as the binary chalcogenide Bi2X3 (X=Te or Se) has yielded novel two-dimensional electron-gas physics, phase transitions to superconductivity, as well as interesting…
We report point contact measurements in high quality single crystals of Cu0.2Bi2Se3. We observe three different kinds of spectra: (1) Andreev-reflection spectra, from which we infer a superconducting gap size of 0.6mV; (2) spectra with a…
In this article, a brief introduction is first given on infrared studies of materials at high pressures using a diamond anvil cell. Then, our recent results of high-pressure infrared studies are described for Mg$_2$Si, InAs, and InSb. For…
Pressure dependence of the electronic and crystal structures of K$_{x}$Fe$_{2-y}$Se$_{2}$, which has pressure-induced two superconducting domes of SC I and SC II, was investigated by x-ray emission spectroscopy and diffraction. X-ray…