ABSTRACT
Interfaces between materials with differently ordered phases present unique opportunities for exotic physical properties, especially the interplay between ferromagnetism and superconductivity in the ferromagnet/superconductor heterostructures. The investigation of zero- and π-junctions has been of particular interest for both fundamental physical science and emerging technologies. Here, we report the experimental observation of giant oscillatory Gilbert damping in the superconducting niobium/nickel-iron/niobium junctions with respect to the nickel-iron thickness. This observation suggests an unconventional spin pumping and relaxation via zero-energy Andreev bound states that exist not only in the niobium/nickel-iron/niobium π-junctions but also in the niobium/nickel-iron/niobium zero-junctions. Our findings could be important for further exploring the exotic physical properties of ferromagnet/superconductor heterostructures and potential applications of ferromagnet π-junctions in quantum computing, such as half-quantum flux qubits.
ABSTRACT
Spin current historically referred to the flow of electrons carrying spin information, in particular since the discovery of giant magnetoresistance in the 1980s. Recently, it has been found that spin current can also be mediated by spin-triplet supercurrent, superconducting quasiparticles, spinons, magnons, spin superfluidity and so on. Here, we review key progress concerning the developing research direction utilizing spin current as a probe of quantum materials. We focus on spin-triplet superconductivity and spin dynamics in the ferromagnet/superconductor heterostructures, quantum spin liquids, magnetic phase transitions, magnon-polarons, magnon-polaritons, magnon Bose-Einstein condensates and spin superfluidity. The unique characteristics of spin current as a probe will be fruitful for future investigation of spin-dependent properties and the identification of new quantum materials.
ABSTRACT
Objective To summarize clinical experience and explore application value of endoscopic clipping with histoacryl using in management of type 2 gastroesophageal varices. Methods Clinical data of 30 patients with type 2 gastroesophageal varices patients (including acute hemorrhage and primary prevention) from May 2015 to December 2016 were collected. Then evaluate therapeutic effect and safety of endoscopic clipping adjuvant therapy. Results Average glue dosage was (1.46 ± 0.70) ml, average using of clips were (5 ~ 6), and intraoperative needle pulling hemorrhage occurred in 2 cases. 14 patients (46.7%) underwent endoscopic re-examination, 3 patients (10.0%) achieved varicose vein elimination, 11 cases (36.7%) remained residual. Rebleeding occurred in 4 cases (13.3%), and 2 cases died (6.7%), one because of postoperative hematemesis and hemorrhagic shock, the other one died of spontaneous peritonitis and septic shock. For general curative effect, 2 cases (6.7%) were healed, 22 cases (73.3%) were improved, and 6 cases were unhealed (20.0%, 4 cases occurred rebleeding, 2 cases died); 17 cases underwent CT portal venograpy, abnormal embolization was not found in any patients, glue extrusion bleeding occurred in 1 case (3.3%), no patients had severe postoperative complications. Conclusion Endoscopic clipping with histoacryl can be used in the prevention and treatment of type 2 gastroesophageal varices to improve the treatment effect and reduce postoperative bleeding risk, may have good clinical practice value.
ABSTRACT
The topological insulator/normal insulator (TI/NI) superlattices (SLs) with multiple Dirac channels are predicted to offer great opportunity to design novel materials and investigate new quantum phenomena. Here, we report first transport studies on the SLs composed of TI Bi2Se3 layers sandwiched by NI In2Se3 layers artificially grown by molecular beam epitaxy (MBE). The transport properties of two kinds of SL samples show convincing evidence that the transport dimensionality changes from three-dimensional (3D) to two-dimensional (2D) when decreasing the thickness of building block Bi2Se3 layers, corresponding to the crossover from coherent TI transport to separated TI channels. Our findings provide the possibility to realizing "3D surface states" in TI/NI SLs.
ABSTRACT
We study the spin-1/2 J1-J2 Heisenberg model on a square lattice using the cluster mean-field theory. We find a rapid convergence of phase boundaries with increasing cluster size. By extrapolating the cluster size L to infinity, we obtain accurate phase boundaries J(c1)(2) ≈ 0.42 (between the Néel antiferromagnetic phase and non-magnetic phase), and J(c2)(2) ≈ 0.59 (between non-magnetic phase and the collinear antiferromagnetic phase). Our results support the second-order phase transition at J(c1)(2) and the first-order one at J(c2)(2). For the spin-anisotropic J1-J2 model, we present its finite temperature phase diagram and demonstrate that the non-magnetic state is unstable towards the first-order phase transition under intermediate spin anisotropy.
