Current methods of chemical vapour deposition (CVD) graphene on copper are complicated by multiple processing steps and high temperatures required in both preparing the inducing subsequent film growth. Here we demonstrate a plasma-enhanced CVD chemistry that enables entire process to take place single step, at reduced (<420 °C), matter minutes. Growth foils is found nucleate from arrays well-aligned domains, ensuing films possess sub-nanometre smoothness, excellent crystalline quality, low...

We report directional tunneling and point-contact spectroscopy measurements on the ${100}$, ${110}$, ${001}$ faces of ${\mathrm{YBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ single crystals at 4.2 K. The conductance spectra show fully developed quasiparticle tunneling, Andreev reflection, zero-bias peak characteristics, depending systematically junction orientation impedance. Quantitative spectral analysis using generalized formalism Blonder, Tinkham, Klapwijk...

We have used in situ resistivity measurements to monitor the diffusion of oxygen and out ceramic oxide $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$. The study out-diffusion was carried by annealing ambient helium at constant heating rates temperatures. rate has been found be independent $\ensuremath{\delta}$, changes linearly with time during isothermal anneals. Assuming that is surface reaction limited, we determined a barrier 1.7 eV....

We report a direct observation of surface dominated conduction in an intrinsic Bi(2)Se(3) thin film with thickness six quintuple layers grown on lattice-matched CdS (0001) substrates by molecular beam epitaxy. Shubnikov-de Haas oscillations from the topological states suggest that Fermi level falls inside bulk band gap and is 53 ± 5 meV above Dirac point, which agreement 70 20 obtained scanning tunneling spectroscopies. Our results demonstrate great potential producing genuine insulator...

A detailed study of the electrical transport properties in high-quality bulk single crystals ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ has manifested a Kosterlitz-Thouless (K-T)--type transition ab plane 0.2 K below mean-field superconducting (${T}_{c}^{0}$=93.15 K). The c-axis correlation length ${l}_{c}$(T=0)\ensuremath{\simeq}6 A\r{} and large two-dimensional effective mass (${m}_{\mathrm{ab}}^{\mathrm{*}}$/${m}_{e}$\ensuremath{\sim}10) supercarrier are estimated based on...

We demonstrate evidence of a surface gap opening in topological insulator (TI) thin films (Bi(0.57)Sb(0.43))(2)Te(3) below six quintuple layers through transport and scanning tunneling spectroscopy measurements. By effective tuning the Fermi level via gate-voltage control, we unveil striking competition between weak localization antilocalization at low magnetic fields nonmagnetic ultrathin films, possibly owing to change net Berry phase. Furthermore, when is swept into samples, overall...

Graphene has emerged as an electronic material that is promising for device applications and studying two-dimensional electron gases with relativistic dispersion near two Dirac points. Nonetheless, deviations from Dirac-like spectroscopy have been widely reported varying interpretations. Here we show evidence strain-induced spatial modulations in the local conductance of single-layer graphene on SiO2 substrates scanning tunneling microscopic (STM) studies. We find strained exhibits...

The realization of many promising technological applications graphene and graphene-based nanostructures depends on the availability reliable, scalable, high-yield low-cost synthesis methods. Plasma enhanced chemical vapor deposition (PECVD) has been a versatile technique for synthesizing carbon-based materials, because PECVD provides rich environment, including mixture radicals, molecules ions from hydrocarbon precursors, which enables growth variety material surfaces at lower temperatures...

Controlling the density of exciton and trion quasiparticles in monolayer two-dimensional (2D) materials at room temperature by nondestructive techniques is highly desired for development future optoelectronic devices. Here, effects different orbital angular momentum (OAM) lights on tungsten disulfide both low temperatures are investigated, which reveal simultaneously enhanced intensity suppressed photoluminescence spectra with increasing topological charge OAM light. In addition,...

We report phenomena manifesting nonequilibrium superconductivity induced by spin-polarized quasiparticles in perovskite ferromagnet-insulator-superconductor (F-I-S) heterostructures. Measurements of the critical current ${J}_{c},$ using a pulsed technique to minimize Joule heating, reveal monotonic increase with increasing insulator thickness; and for F-I-S thin insulating barriers, slight ${J}_{c}$ is observed under small injection currents ${I}_{m}$ from ferromagnet, followed strong...

Scanning tunneling spectroscopy (STS) studies reveal long-range spatial homogeneity and predominantly $d_{x^2-y^2}$-pairing spectral characteristics in under- optimally doped $\rm YBa_2Cu_3O_{7-\delta}$ superconductors, whereas STS on YBa_2(Cu_{0.9934}Zn_{0.0026}Mg_{0.004})_3O_{6.9}$ exhibits {\it microscopic} modulations strong scattering near the Zn or Mg impurity sites, together with global suppression of pairing potential. In contrast, overdoped (Y_{0.7}Ca_{0.3})Ba_2Cu_3O_{7-\delta}$,...

Direct experimental evidence of half-metallic density states (DOS) is observed by scanning tunneling spectroscopy on ferromagnetic ${\mathrm{La}}_{0.7}{\mathrm{Ca}}_{0.3}{\mathrm{MnO}}_{3}$, which exhibits colossal magnetoresistance (CMR). Tunneling conductance data taken at 77 K, well below the Curie temperature ${T}_{C}\ensuremath{\approx}260\mathrm{K}$, show close resemblance to spin-split DOS spectrum calculated for itinerant bands in state. The spectral characteristics are absent...

Experimental evidence of a Bose-glass transition in the vortex state ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7}$ single crystals with columnar defects along c axis is manifested by universal critical exponents ${\ensuremath{\nu}}_{\mathrm{\ensuremath{\perp}}}$, ${\ensuremath{\nu}}_{\mathrm{\ensuremath{\parallel}}}$ (\ensuremath{\equiv}\ensuremath{\zeta}${\ensuremath{\nu}}_{\mathrm{\ensuremath{\perp}}}$), and z' derived from (d'+1)-dimension scaling frequency-dependent ac...

Monolayer transition-metal dichalcogenides (TMDCs) in the 2H-phase are promising semiconductors for opto-valleytronic and opto-spintronic applications because of their strong spin-valley coupling. Here, we report detailed studies properties heterogeneous domains CVD-grown monolayer WS2 single crystals. By illuminating with off-resonance circularly polarized light measuring resulting spatially resolved emission (Pcirc), find significantly large circular polarization (Pcirc up to 60% 45% α-...

Scanning tunneling spectroscopic studies of $Ba(Fe_{1-x}Co_x)_2As_2$ (x = 0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition $T_c$. The nature slightly doping- energy-dependent quasiparticle scattering interferences near wave-vectors $(\pm \pi, 0)$ $(0, \pm \pi)$ are consistent sign-changing $s$-wave excess zero-bias conductance large gap-to-$T_c$...

Hexagonal boron nitride (h-BN) is a promising two-dimensional insulator with large band gap and low density of charged impurities that isostructural isoelectronic graphene. Here we report the chemical atomic-scale structure CVD-grown wafer-scale (∼25 cm2) h-BN sheets ranging in thickness from 1 to 20 monolayers. Atomic-scale images on Au graphene/Au substrates obtained by scanning tunneling microscopy reveal high crystalline quality monolayer samples. Further characterization 1–20 samples...

The research field of topological phases and materials is one the most exciting frontiers in modern condensed matter physics [1]; [2]; [3]; [4]; [5]; [6] ; [7]. In contrast to classification conventional according their symmetries, different states generally do not involve broken symmetries. Rather, they are associated with certain fundamental physical properties that insensitive smooth changes parameters. Therefore, a state cannot change into another unless system undergoes quantum phase transition

The existence of nontrivial Berry phases associated with two inequivalent valleys in graphene provides interesting opportunities for investigating the valley-projected topological states. Examples such studies include observation anomalous quantum Hall effect monolayer graphene, demonstration zero modes molecular assembled by scanning tunneling microscopy, and detection valley transport either superlattices or at bilayer domain walls. However, all aforementioned experiments involved...

Monolayer transition metal dichalcogenides (TMDs) have intrinsic valley degrees of freedom, making them appealing for exploiting valleytronic applications in information storage and processing. WS2 monolayer possesses two inequivalent valleys the Brillouin zone, each coupling selectively with a circular polarization light. The degree (DVP) under excitation circularly polarized light (CPL) is parameter that determines purity photoluminescence (PL) . Here efficient tailoring valley-polarized...

Quasiparticle tunneling spectra of the electron-doped (n-type) infinite-layer cuprate Sr_{0.9}La_{0.1}CuO_2 reveal characteristics that counter a number common phenomena in hole-doped (p-type) cuprates. The optimally doped with T_c = 43 K exhibits momentum-independent superconducting gap \Delta 13.0 +- 1.0 meV substantially exceeds BCS value, and spectral indicate insignificant quasiparticle damping by spin fluctuations absence pseudogap. response to quantum impurities Cu-sites also differs...

The critical fluctuations and pinning effects in the vortex state of twinned superconducting Y-Ba-Cu-O single crystals are investigated. A second-order vortex-solid melting transition is manifested by universal static dynamic exponents \ensuremath{\nu}\ensuremath{\approxeq}2/3 z\ensuremath{\approxeq}3 vortex-transport functions, independent experimental techniques magnitude orientation applied magnetic fields. vortex-correlation length critical-relaxation rate also determined.

The high-frequency vortex dynamics of high-temperature superconductors near the flux-line depinning threshold is investigated based on a thermally activated flux-flow (TAFF) model. Dissipation due to motion driven by microwave electromagnetic field studied as function frequency, temperature, dc magnetic field, and power. generalized TAFF model also compared conventional flux-creep theory found qualitatively consistent.