Magnetic field can penetrate into type II superconductors in the form of Abrikosov vortices, which are magnetic flux tubes surrounded by circulating supercurrents often trapped at defects referred to as pinning sites. Although the average properties of the vortex matter in superconductors can be tuned with magnetic fields, temperature or electric currents, handling of individual Abrikosov vortices remains challenging and has been demonstrated only with sophisticated scanning local probe microscopies. Here we introduce a far-field optical method based on local heating of the superconductor with a focused laser beam to realize a fast and precise manipulation of individual vortices, in the same way as with optical tweezers. This simple approach provides the perfect basis for sculpting the magnetic flux profile in superconducting devices like a vortex lens or a vortex cleaner, without resorting to static pinning or ratchet effects.

Three independent components of critical current density, one for the H//c axis and the other two for the H//ab plane, have been studied in CaKFe 4 As 4 single crystals. When the magnetic field is applied along the c axis, we observed fish-tail-like peaks in the M-H hysteresis loop, and the magnetization at higher temperatures exceeds that at lower temperatures at high fields. When the field is applied parallel to the ab plane, a dip structure is observed in the M-H hysteresis loop near the self-field. In addition, for the H//ab plane, we succeeded in separately evaluating the large and significantly anisotropic in-plane and out-of-plane J c . Transmission electron microscopy revealed the presence of planar defects parallel to the ab plane in CaKFe 4 As 4 , which have not been observed in any other iron-based superconductors. We discuss the possible relationship between the anomalous J c behavior and the planar defects. anisotropy parameter  = H c2 ab /H c2 c is evaluated from the temperature dependence of H c2 (T). The temperature dependences of H c2 are summarized in Fig. 2(c). The definitions of T c onset and T c end are shown in Fig. 2(a). Estimated  at T ~ 34 K is 2.2. This value is consistent with the former report by Meier et al. [12], and similar to that of 122-type compounds of (Ba,K)Fe 2 As 2 with  ~ 2-3 near T c [4]. Next we performed magneto-optical (MO) imaging of a CaKFe 4 As 4 single crystal to evaluate its homogeneity and the value of in-plane J c . Figure 3(c) shows an optical micrograph of the crystal, which shows a smooth surface with no visible cracks. Figures 3(a) and 3(b) display MO images of the CaKFe 4 As 4 single crystal in the remanent state at (a) 5 K and (b) 35 K, respectively, after cycling the field up to 1.6 kOe for 0.2 s. At 5 K, the magnetic field does not fully penetrate the sample because of large J c and limitation of the value of the applied field. On the other hand, the magnetic field fully penetrates the sample at 35 K, and the MO image shows the critical state field profile expected for a uniform thin-plate superconductor with clear current discontinuity lines (d-lines).Local magnetic induction profiles at different temperatures taken along the dotted line in Fig. 3(a) are shown in Fig. 3(d). Magnetic induction profiles at higher temperatures of 30 and 35 K show roof-top patterns, indicating that the large and homogeneous current flows throughout the sample. At lower temperatures, however, the magnetic induction profiles are saturated around 700 G because of large J c and the saturation of the magnetization of the indicator film. From the value of the trapped field, J c can be roughly evaluated [19]. At 30 K, magnetic induction B of 580 G is trapped. Using t l l c (0<<1) = 1 H J c2 J c3 H t l l c (0<<1) = 2 J c2 J c3 (c) (d)