Related papers: Vortex pinning and dynamics in high performance Sr…
Vortex pinning is a crucial factor that determines the critical current of practical superconductors and enables their diverse applications. However, the underlying mechanism of vortex pinning has long been elusive, lacking a clear…
Superconducting performance is tunable not only via chemical modification or defect engineering, but also through external parameters such as pressure, though this method remains less readily accessible. In this work, we study how…
We have studied the isothermal magnetization $M(H)$ of CeCo(In$_{1-x}$Cd$_x$)$_5$ with $x$ = 0.0075 and 0.01 down to 50 mK. Pronounced field-history dependent phenomena occur in the coexistence regime of the superconducting and…
The evolution of the vortex glass (VG) phase transition and vortex creep with decreasing film thickness is studied in ultrathin, polycrystalline niobium films, with thickness in the range 7.4 nm to 44 nm, using current-voltage…
We have conducted extensive investigations on the magnetization and its dynamical relaxation on a Ba$_{0.66}$K$_{0.32}$BiO$_{3+\delta}$ single crystal. It is found that the magnetization relaxation rate is rather weak compared with that in…
122 type pnictide superconductors are of particular interest for high-field applications because of their large upper critical fields Hc2 (> 100 T), low Hc2 anisotropy r (< 2), and high thin-film critical current densities Jc (> 1 MA/cm2 at…
We report on the superior vortex pinning of single and multilayer Ba(Fe1-xCox)2As2 thin films with self-assembled c-axis and artificially introduced ab-plane pins. Ba(Fe1-xCox)2As2 can accept a very high density of pins (15-20 vol%) without…
We report that single crystals of (Ba,K)Fe2As2 with Tc = 32 K have a pinning potential, U0, as high as 10^4 K, with U0 showing very little field depend-ence. In addition, the (Ba,K)Fe2As2 single crystals become isotropic at low temperatures…
Magnetization and its relaxation have been measured in $Ba(Fe_{1-x}Co_x)_2As_2$ single crystals at various doping levels ranging fromvery underdoped to very overdoped regimes. Sizable magnetization relaxation rate has been observed in all…
We report measurements of the field and angular dependences of Jc of truly epitaxial Co-doped BaFe2As2 thin films grown on SrTiO3/(La,Sr)(Al,Ta)O3 with different SrTiO3 template thicknesses. The films show Jc comparable to Jc of single…
The work reported in my doctoral thesis is an experimental study of vortex dynamics and phase transitions in thin films of type II superconductors using scanning tunneling spectroscopy, low frequency ac susceptibility measurements and…
We identify a phase transition in the vortex system of a high-temperature superconductor with nano-columnar stacks of precipitates as strong vortex pinning centers. Above a particular, temperature-dependent field $B_X(T)$ the vortex…
We present a comprehensive overview of vortex pinning in single crystals of the isovalently substituted iron-based superconductor BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, a material that qualifies as an archetypical clean superconductor,…
Mechanisms of vortex dynamics and pinning and self-field effects which could account for the thickness dependence of the critical current density J_c of superconducting films are addressed. It is shown that at low magnetic fields B, the 2D…
One important factor affecting the critical current density in type-II superconductors is the formation of artificial pinning centers. Hence, the engineering of pinning centers in superconducting systems has garnered considerable attention.…
We examine vortex pinning and dynamics in thin-film superconductors interacting with square and rectangular pinning arrays for varied vortex densities including densities significantly larger than the pinning density. For both square and…
The interactions between vortices in a thin superconducting film and one magnetic dipole in the presence of a magnetic field applied parallel to the film surfaces are studied theoretically in the London limit. The dipole magnetic moment is…
We report numerical simulations of a trapped elastic vortex driven by a strong ac magnetic field $H(t)=H\sin\omega t$ parallel to the surface of a superconducting film. The surface resistance and the power dissipated by an oscillating…
We report on isofield magnetic relaxation data on a single crystal of $Ba_{1-x}K_xFe_2As_2$ with superconducting transition temperature $T_c$= 32.7 K which exhibit the so called fish-tail effect. A surface map of the superconducting…
We report on the thickness dependence of the superconducting characteristics including critical current Ic, critical current density Jc, transition temperature Tc, irreversibility field Hirr, bulk pinning force plot Fp(H), and the normal…