We present a phase diagram as function of disorder in three-dimensional NbN thin films, the system enters critical for destruction superconducting state. The state is investigated using combination magnetotransport and tunneling spectroscopy measurements. Our studies reveal 3 different regimes. At low (k_{F}l~10-4), follows mean field Bardeen-Cooper-Schrieffer behavior where energy gap vanishes at temperature electrical resistance appears. For stronger (k_{F}l<4) "pseudogap" emerges...

We investigate evolution of the magnetic penetration depth and superconducting energy gap in epitaxial NbN films using a low frequency mutual inductance technique tunneling spectroscopy temperature scanning microscope (STM). The transition (Tc) for grown under optimal growth conditions decreases monotonically from 15.87K to 9.16K as film thickness is decreased 50nm 3nm. With decrease delta(0) decreases, whereas lambda(0) increases. observe that Tc, lambda(o) are well described by...

The hexatic fluid refers to a phase in between solid and liquid that has short-range positional order but quasi-long-range orientational order. In the celebrated theory of Berezinskii, Kosterlitz, Thouless subsequently refined by Halperin, Nelson, Young, it was predicted two-dimensional hexagonal can melt two steps: first, through transformation from fluid, which retains order; then an isotropic liquid. this Letter, using combination real space imaging transport measurements, we show vortex...

The most common allotrope of tungsten, $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{W}$, has a superconducting transition at temperature $\ensuremath{\sim}11\phantom{\rule{0.16em}{0ex}}\mathrm{mK}$. However, two other forms tungsten have been reported to transitions in the range ${T}_{c}\ensuremath{\sim}2\ensuremath{-}5\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ when synthesized as thin films: crystalline $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{W}$ and amorphous W...

ZnO nanostructured films were prepared by chemical bath deposition method on glass substrates without any assistance of either microwave or high pressure autoclaves. The effect solute concentration the pure wurtzite nanostructure morphologies is studied. controlling help to control nano-structure in form nano-needles, and rods.

We measure the frequency dependence of complex ac conductivity NbN films with different levels disorder in range 0.4-20 GHz. Films low exhibit a narrow dynamic fluctuation regime above T_c as expected for conventional superconductor. However, strongly disordered samples, extends well T_c, frequency-dependent superfluid stiffness which disappears only at temperature T* close to pseudogap obtained from scanning tunneling measurements. Such finite-frequency response is associated marked slowing...

Abstract The vortex lattice in a Type II superconductor provides versatile model system to investigate the order-disorder transition periodic medium presence of random pinning. Here, using scanning tunnelling spectroscopy weakly pinned Co 0.0075 NbSe 2 single crystal, we show that 3-dimensional disorders through successive destruction positional and orientational order, as magnetic field is increased across peak effect. At onset effect, equilibrium quasi-long range ordered state transforms...

We report the temperature dependence of resistivity $(\ensuremath{\rho})$ and Hall coefficient $({R}_{H})$ in normal state homogeneously disordered epitaxial NbN thin films with ${k}_{F}l\ensuremath{\sim}1.68--10.12$. The superconducting transition $({T}_{c})$ these varies from 2.7 to 16.8 K. While our least film displays usual metallic behavior, for all ${k}_{F}l\ensuremath{\le}8.13$, both $\frac{d\ensuremath{\rho}}{dT}$ $\frac{d{R}_{H}}{dT}$ are negative up 285 observe that${R}_{H}(T)$...

We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350 mK in magnetic fields up 9 T, with thin film deposition situ single crystal cleaving capabilities. The main focus lies on simple design STM head sample holder that allows us get spectroscopic data superconducting films grown insulating substrates. Other details transport, preparation chamber, vibration isolation schemes are also described. demonstrate...

Abstract We investigate the low-frequency electrodynamics in vortex state of two type-II superconducting films, namely, a moderate-to-strongly pinned Niobium Nitride (NbN) and very weakly amorphous Molybdenum Germanium ( -MoGe) film. employ two-coil mutual inductance technique to extract complex penetration depth, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mover> <mml:mi>λ</mml:mi> <mml:mo stretchy="true">~</mml:mo> </mml:mover> </mml:mrow>...

Recently, detailed real-space imaging using scanning tunneling spectroscopy of the vortex lattice in a weakly pinned $a$-MoGe thin film revealed that melts two steps with temperature or magnetic field, going first from solid to hexatic fluid and then an isotropic liquid. In this paper, we show resistance state is extremely sensitive radio-frequency electromagnetic perturbation. presence very low-amplitude excitation above few kilohertz, increases by several orders magnitude. On other hand,...

Disorder induced melting, where the increase in positional entropy created by random pinning sites drives order-disorder transition a periodic solid, provides an alternate route to more conventional thermal melting. Here, using real space imaging of vortex lattice through scanning tunneling spectroscopy, we show that presence weak pinning, type II superconductor disorders two distinct topological transitions. Across each transition, separately identify metastable states formed superheating...

We present the first observation of dynamically modulated quantum phase transition between two distinct charge density wave (CDW) phases in two-dimensional $2H\text{\ensuremath{-}}{\mathrm{NbSe}}_{2}$. There is recent spectroscopic evidence for presence these phases, but its bulk measurements remained elusive. studied suspended, ultrathin $2H\text{\ensuremath{-}}{\mathrm{NbSe}}_{2}$ devices fabricated on piezoelectric substrates---with tunable flakes thickness, disorder level, and strain....

We investigate the evolution of superconductivity with decreasing film thickness in ultrathin amorphous MoGe (a-MoGe) films using a combination sub-Kelvin scanning tunneling spectroscopy, magnetic penetration depth measurements and magneto-transport measurements. observe that is strongly affected by quantum classical phase fluctuations for below 5 nm. The superfluid density suppressed at low temperatures evolves towards linear-T dependence higher temperatures. This associated rapid decrease...

We report the experimental observation of Ising superconductivity in three-dimensional ${\mathrm{NbSe}}_{2}$ stacked with single-layer ${\mathrm{MoS}}_{2}$. The angular dependence upper critical magnetic field and temperature parallel confirm appearance two-dimensional a ${\mathrm{MoS}}_{2}$ overlay. show that superconducting phase has strong spin-orbit correlations which make holes spin nondegenerate. Our heterostructures few-layer thickness $\ensuremath{\sim}15$ nm raises interesting...

Real space imaging using a scanning tunnelling microscope reveals the formation of an inhomogeneous vortex liquid state in few nanometer thick superconducting films that does not freeze into crystal or glass down to 0.41 $K$. Vortices this two-dimensional form network percolating paths, due combined effect pinning and intervortex interaction. While some vortices remain static, others move on network, with their relative fractions changing magnetic field, temperature, applied current.

We investigate the magnetic field variation of thermally activated flux flow resistivity, ρ TAFF and critical current density, J c, in a weakly pinned thin film amorphous superconductor a-MoGe, where vortices are fluid state over large range fields. show that both quantities can be understood within framework collective pinning theory. In particular, our results demonstrate 'peak effect' arise at order-disorder transition vortex lattice even when ordered disordered states fluids, such as...

Although matching effects in superconducting anti-dot arrays have been studied extensively through magneto-resistance oscillations, these investigations restricted to a very narrow temperature window close the transition. Here, we report “two coil” mutual inductance technique, which allows study of this phenomenon deep state, direct measurement magnetic field variation shielding response. We demonstrate how technique can be used resolve outstanding issues on origin thin films with periodic...

We report the effect of electric current and magnetic field, separately in conjugation, on transport behaviour patterned La0.7Ce0.3MnO3 thin films. In absence a significant reduction peak resistance (Rp) was found with increasing bias current. This is also present when field applied, though magnitude electroresistance (ER = [R(I 0.05 µA)−R(I 50 µA)]/R(I µA)) decreases. The metal–insulator transition temperature (Tp) increases both field. observe an interesting correlation between field:...

Superconductivity in granular films is controlled by the grain size and inter-grain coupling. In a two-component system formed random mixture of normal metal (N) superconductor (S), superconducting nano-grains may become coupled through S-N weak links, thereby affecting properties network. We report on study superconductivity immiscible Nb-Cu nanocomposite with varying compositions. The microstructure revealed presence phase separated, closely spaced, Nb Cu whose sizes changed marginally...

We have investigated the dynamics of vortices at subcritical microwave currents in dc magnetic fields (up to 0.8 T) epitaxial ${\mathrm{DyBa}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (DBCO) thin films. Microwave measurements were performed using microstrip resonators as test vehicles 4.88 GHz and 9.55 on laser ablated DBCO films thickness range 1800--3800 \AA{}. Experimental evidence indicates that peak effect (PE) observed surface resistance vs temperature...

The influence of electric current on the transport behaviour La0.7Ce0.3MnO3 thin epitaxial films (001) LaAlO3 substrate is studied. Measurements were carried out in regime low densities (0.0325–32.5 A cm−2), for dc absence magnetic field. Significant reduction peak resistance (Rp) with monotonic increase metal–insulator transition temperature (Tp) was found increasing bias current. voltage characteristics at various temperatures above and below Tp show nonlinearity small currents. behaviours...