We report a successful observation of pressure-induced superconductivity in a topological compound Bi ₂ Te ₃ with T _c of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the hole-type carrier in the pressure-induced superconducting Bi ₂ Te ₃ single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi ₂ Te ₃ due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor.

Searching for superconductivity with T_c near room temperature is of great interest both for fundamental science & many potential applications. Here we report the experimental discovery of superconductivity with maximum critical temperature (T_c) above 210 K in calcium superhydrides, the new alkali earth hydrides experimentally showing superconductivity above 200 K in addition to sulfur hydride & rare-earth hydride system. The materials are synthesized at the synergetic conditions of 160~190 GPa and ~2000 K using diamond anvil cell combined with in-situ laser heating technique. The superconductivity was studied through in-situ high pressure electric conductance measurements in an applied magnetic field for the sample quenched from high temperature while maintained at high pressures. The upper critical field Hc(0) was estimated to be ~268 T while the GL coherent length is ~11 Å. The in-situ synchrotron X-ray diffraction measurements suggest that the synthesized calcium hydrides are primarily composed of CaH₆ while there may also exist other calcium hydrides with different hydrogen contents.

The cubic perovskite BaRuO ₃ has been synthesized under 18 GPa at 1,000°C. Rietveld refinement indicates that the new compound has a stretched Ru–O bond. The cubic perovskite BaRuO ₃ remains metallic to 4 K and exhibits a ferromagnetic transition at T _c = 60 K, which is significantly lower than the T _c ≈ 160 K for SrRuO ₃ . The availability of cubic perovskite BaRuO ₃ not only makes it possible to map out the evolution of magnetism in the whole series of ARuO ₃ (A = Ca, Sr, Ba) as a function of the ionic size of the A-site r _A, but also completes the polytypes of BaRuO ₃ . Extension of the plot of T _c versus r _A in perovskites ARuO ₃ (A = Ca, Sr, Ba) shows that T _c does not increase as the cubic structure is approached, but has a maximum for orthorhombic SrRuO ₃ . Suppressing T _c by Ca and Ba doping in SrRuO ₃ is distinguished by sharply different magnetic susceptibilities χ( T ) of the paramagnetic phase. This distinction has been interpreted in the context of a Griffiths' phase on the (Ca Sr)RuO ₃ side and bandwidth broadening on the (Sr,Ba)RuO ₃ side.

Diluted magnetic semiconductors have received much attention due to their potential applications for spintronics devices. A prototypical system (Ga,Mn)As has been widely studied since the 1990s. The simultaneous spin and charge doping via hetero-valent (Ga³⁺,Mn²⁺) substitution, however, resulted in severely limited solubility without availability of bulk specimens. Here we report the synthesis of a new diluted magnetic semiconductor (Ba_1−xK_x)(Zn_1−yMn_y)₂As₂, which is isostructural to the 122 iron-based superconductors with the tetragonal ThCr₂Si₂ (122) structure. Holes are doped via (Ba²⁺, K¹⁺) replacements, while spins via isovalent (Zn²⁺,Mn²⁺) substitutions. Bulk samples with x=0.1−0.3 and y=0.05−0.15 exhibit ferromagnetic order with T_C up to 180 K, which is comparable to the highest T_C for (Ga,Mn)As and significantly enhanced from T_C up to 50 K of the ‘111’-based Li(Zn,Mn)As. Moreover, ferromagnetic (Ba,K)(Zn,Mn)₂As₂ shares the same 122 crystal structure with semiconducting BaZn₂As₂, antiferromagnetic BaMn₂As₂ and superconducting (Ba,K)Fe₂As₂, which makes them promising for the development of multilayer functional devices.

The recently discovered Dirac and Weyl semimetals are new members of topological materials. Starting from them, topological superconductivity may be achieved, e.g., by carrier doping or applying pressure. Here we report high-pressure resistance and X-ray diffraction study of the three-dimensional topological Dirac semimetal Cd₃As₂. Superconductivity with T_c≈2.0 K is observed at 8.5 GPa. The T_c keeps increasing to about 4.0 K at 21.3 GPa, then shows a nearly constant pressure dependence up to the highest pressure 50.9 GPa. The X-ray diffraction measurements reveal a structure phase transition around 3.5 GPa. Our observation of superconductivity in pressurised topological Dirac semimetal Cd₃As₂ provides a new candidate for topological superconductor, as argued in a recent point contact study and a theoretical work.

In a prototypical ferromagnet (Ga,Mn)As based on a III–V semiconductor, substitution of divalent Mn atoms into trivalent Ga sites leads to severely limited chemical solubility and metastable specimens available only as thin films. The doping of hole carriers via (Ga,Mn) substitution also prohibits electron doping. To overcome these difficulties, Masek et al. theoretically proposed systems based on a I–II–V semiconductor LiZnAs, where isovalent (Zn,Mn) substitution is decoupled from carrier doping with excess/deficient Li concentrations. Here we show successful synthesis of Li_1+y(Zn_1−xMn_x)As in bulk materials. Ferromagnetism with a critical temperature of up to 50 K is observed in nominally Li-excess (y=0.05–0.2) compounds with Mn concentrations of x=0.02–0.15, which have p-type metallic carriers. This is presumably due to excess Li in substitutional Zn sites. Semiconducting LiZnAs, ferromagnetic Li(Zn,Mn)As, antiferromagnetic LiMnAs, and superconducting LiFeAs systems share square lattice As layers, which may enable development of novel junction devices in the future.