Jia Yu

Bio: Jia Yu is an academic researcher from Sun Yat-sen University. The author has contributed to research in topics: Superconductivity & Antiferromagnetism. The author has an hindex of 8, co-authored 31 publications receiving 212 citations. Previous affiliations of Jia Yu include Chinese Academy of Sciences.

Ion-exchange synthesis and superconductivity at 8.6 K of Na2Cr3As3 with quasi-one-dimensional crystal structure

Abstract: A new Cr-based quasi-one-dimensional superconductor Na2Cr3As3 was synthesized by an ion-exchange method in sodium naphthalenide solution. The crystals are thread-like and the structure was analyzed by X-ray diffraction with a noncentrosymmetric hexagonal space group P-6m2 (No. 187), in which the (Cr3As3)2- linear chains are separated by Na+ ions, and the refined lattice parameters are a = 9.239(2) A and c = 4.209(6) A. The measurements for electrical resistivity, magnetic susceptibility, and heat capacity reveal a superconducting transition with unconventional characteristic at the Tc of 8.6 K, which exceeds that of all previously reported Cr-based superconductors.

Superconductivity at 7.3 K in the 133-type Cr-based RbCr3As3 single crystals

Abstract: Here we report the preparation and superconductivity of the 133-type Cr-based quasi–one-dimensional (Q1D) RbCr3As3 single crystals. The samples were prepared by the deintercalation of Rb+ ions from the 233-type Rb2Cr3As3 crystals which were grown from a high-temperature solution growth method. The RbCr3As3 compound crystallizes in a centrosymmetric structure with the space group P63/m (No. 176) different from its non-centrosymmetric Rb2Cr3As3 superconducting precursor, and the refined lattice parameters are and . Electrical resistivity and magnetic susceptibility characterizations reveal the occurrence of superconductivity with an interestingly higher onset T c of 7.3 K than other Cr-based superconductors, and an estimated high upper critical field H c2(0) about 72.4 T in this 133-type RbCr3As3 crystals.

Discovery of a novel 112-type iron-pnictide and La-doping induced superconductivity in Eu1−xLaxFeAs2 (x = 0–0.15)

Abstract: We report the discovery and characterization of a novel 112-type iron pnictide EuFeAs2, with La-doping induced superconductivity in a series of Eu1−xLaxFeAs2. The polycrystalline samples were synthesized through solid state reaction method only within a very narrow temperature window around 1073 K. Small single crystals were also grown from a flux method with the size about 100 μm. The crystal structure was identified by single crystal X-ray diffraction analysis as a monoclinic structure with space group of P21/m. From resistivity and magnetic susceptibility measurements, we found that the parent compound EuFeAs2 shows distinct anomalies probably due to the Fe2+ related antiferromagnetic/structural phase transition near 110 K and the Eu2+ related antiferromagnetic phase transition near 40 K. La-doping suppressed both phase transitions to lower temperatures and induced superconducting transitions with a Tc ∼ 11 K for Eu0.85La0.15FeAs2.

Large negative magnetoresistance in the new antiferromagnetic rare-earth dichalcogenide EuTe$_2$

Abstract: We report the synthesis and characterization of a rare-earth dichalcogenide EuTe$_2$. An antiferromagnetic transition was found at T$_M$ = 11 K. The antiferromagnetic order can be tuned by an applied magnetic field to access a first-order spin flop transition and a spin flip transition. These transitions are associated with a giant negative magnetoresistance with a value of nearly 100\%. Heat capacity measurements reveal strong electronic correlations and a reduced magnetic entropy. Furthermore, density functional theory calculations demonstrate that the electrons near the Fermi surface mainly originate from the Te 5$p$ orbitals and the magnetism is dominated by localized electrons from the Eu 4$f$ orbitals. These results suggest that both the RKKY and Kondo interactions between the local moments and itinerant electrons play crucial roles in the magnetism and large negative magnetoresistance of EuTe$_2$.

Superconductivity at 3.85 K in BaPd2As2 with the ThCr2Si2-type structure

Abstract: The single crystal of ThCr2Si2-type BaPd2As2 was successfully prepared by a self-flux method, and the crystal structure was characterized by X-ray diffraction method with the lattice parameters and (space group , No. 139). Bulk superconductivity below a T c (critical temperature) of 3.85 K was revealed in this compound by the measurements of resistivity, magnetic susceptibility and specific heat, and this T c is much higher than those of other isostructural Pd-based superconductors.

Materials design for new superconductors.

Abstract: Since the announcement in 2011 of the Materials Genome Initiative by the Obama administration, much attention has been given to the subject of materials design to accelerate the discovery of new materials that could have technological implications. Although having its biggest impact for more applied materials like batteries, there is increasing interest in applying these ideas to predict new superconductors. This is obviously a challenge, given that superconductivity is a many body phenomenon, with whole classes of known superconductors lacking a quantitative theory. Given this caveat, various efforts to formulate materials design principles for superconductors are reviewed here, with a focus on surveying the periodic table in an attempt to identify cuprate analogues.

(Sr_3Sc_2O_5)Fe_2As_2 as a possible parent compound for the FeAs-based superconductors

Abstract: A new compound with the FeAs-layers, namely (Sr_3Sc_2O_5)Fe_2As_2 (abbreviated as FeAs-32522), was successfully fabricated. It has a layered structure with the space group of I4/mmm, and with the lattice constants a = 4.069 $\AA$ and c = 26.876 $\AA$. The in-plane Fe ions construct a square lattice which is close to that of other FeAs-based superconductors, such as REFeAsO (RE = rare earth elements) and (Ba,Sr)Fe_2As_2. However the inter FeAs-layer spacing in the new compound is greatly enlarged. The temperature dependence of resistivity exhibits a weak upturn in the low temperature region, but a metallic behavior was observed above about 60 K. The magnetic susceptibility shows also a non-monotonic behavior. Interestingly, the well-known resistivity anomaly which was discovered in all other parent compounds, such as REFeAsO, (Ba,Sr)Fe_2As_2 and (Sr,Ca,Eu)FeAsF and associated with the Spin-Density-Wave (SDW)/structural transition has not been found in the new system either on the resistivity data or the magnetization data. This could be induced by the large spacing distance between the FeAs-planes, therefore the antiferromagnetic correlation between the moments of Fe ions in neighboring FeAs-layers cannot be established. Alternatively it can also be attributed to the self-doping effect between Fe and Sc ions. The Hall coefficient R_H is negative but strongly temperature dependent in wide temperature region, which indicates the dominance of electrical conduction by electron-like charge carriers and probably a multi-band effect or a spin related scattering effect. It is found that the magnetoresistance cannot be described by the Kohler's rule, which gives further support to above arguments.

Ion-exchange synthesis and superconductivity at 8.6 K of N a 2 C r 3 A s 3 with quasi-one-dimensional crystal structure

Abstract: A Cr-based quasi-one-dimensional superconductor $\mathrm{N}{\mathrm{a}}_{2}\mathrm{C}{\mathrm{r}}_{3}\mathrm{A}{\mathrm{s}}_{3}$ was synthesized by an ion-exchange method in a sodium naphthalenide solution. The crystals are threadlike and the structure was analyzed by x-ray diffraction with a noncentrosymmetric hexagonal space group $P\ensuremath{-}6m2$ (No. 187), in which the ${{(\mathrm{C}{\mathrm{r}}_{3}\mathrm{A}{\mathrm{s}}_{3})}^{2}}^{\ensuremath{-}}$ linear chains are separated by $\mathrm{N}{\mathrm{a}}^{+}$ ions, and the refined lattice parameters are $a=9.239(2)\phantom{\rule{0.16em}{0ex}}\AA{}$ and $c=4.209(6)\phantom{\rule{0.16em}{0ex}}\AA{}$. The measurements for electrical resistivity, magnetic susceptibility, and heat capacity reveal a superconducting transition with unconventional characteristic at 8.6 K, which exceeds that of all previously reported Cr-based superconductors.