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 (Ga 3 þ ,Mn 2 þ ) 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 À x K x )(Zn 1 À y Mn y ) 2 As 2 , which is isostructural to the 122 iron-based superconductors with the tetragonal ThCr 2 Si 2 (122) structure. Holes are doped via (Ba 2 þ , K 1 þ ) replacements, while spins via isovalent (Zn 2 þ ,Mn 2 þ ) substitutions. Bulk samples with x ¼ 0.1 À 0.3 and y ¼ 0.05 À 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) 2 As 2 shares the same 122 crystal structure with semiconducting BaZn 2 As 2 , antiferromagnetic BaMn 2 As 2 and superconducting (Ba,K)Fe 2 As 2 , which makes them promising for the development of multilayer functional devices.

In its orthorhombic T d polymorph, MoTe2 is a type-II Weyl semimetal, where the Weyl fermions emerge at the boundary between electron and hole pockets. Non-saturating magnetoresistance and superconductivity were also observed in T d-MoTe2. Understanding the superconductivity in T d-MoTe2, which was proposed to be topologically non-trivial, is of eminent interest. Here, we report high-pressure muon-spin rotation experiments probing the temperature-dependent magnetic penetration depth in T d-MoTe2. A substantial increase of the superfluid density and a linear scaling with the superconducting critical temperature T c is observed under pressure. Moreover, the superconducting order parameter in T d-MoTe2 is determined to have 2-gap s-wave symmetry. We also exclude time-reversal symmetry breaking in the superconducting state with zero-field μSR experiments. Considering the strong suppression of T c in MoTe2 by disorder, we suggest that topologically non-trivial s +− state is more likely to be realized in MoTe2 than the topologically trivial s ++ state.

We employ NMR techniques to investigate the nature of Mn spins in the I-II-V diluted magnetic semiconductor Li(Zn1−xMnx)P (x = 0.1, Curie temperature Tc = 25 K). We successfully identify the 7 Li NMR signals arising from the Li sites adjacent to Mn 2+ , and probe the static and dynamic properties of Mn spins. From the NMR spin-lattice relaxation data, we show that the Mn spin-spin interactions extend over many unit cells.

We report the discovery of a new diluted magnetic semiconductor, Li(Zn,Mn)P, in which charge and spin are introduced independently via lithium off-stoichiometry and the isovalent substitution of Mn 2+ for Zn 2+ , respectively. Isostructural to (Ga,Mn)As, Li(Zn,Mn)P was found to be a p-type ferromagnetic semiconductor with excess Lithium providing charge doping. First principles calculations indicate that excess Li is favored to partially occupy the Zn site, leading to hole doping. Ferromagnetism is mediated in semiconducting samples of relative low mobile carriers with a small coercive force, indicating an easy spin flip.

Understanding the role played by broken-symmetry states such as charge, spin and orbital orders in the mechanism of emergent properties, such as high-temperature superconductivity, is a major current topic in materials research. That the order may be within one unit cell, such as nematic, was only recently considered theoretically, but its observation in the iron-pnictide and doped cuprate superconductors places it at the forefront of current research. Here, we show that the recently discovered BaTi 2 Sb 2 O superconductor and its parent compound BaTi 2 As 2 O form a symmetry-breaking nematic ground state that can be naturally explained as an intra-unit-cell nematic charge order with d-wave symmetry, pointing to the ubiquity of the phenomenon. These findings, together with the key structural features in these materials being intermediate between the cuprate and iron-pnictide hightemperature superconducting materials, render the titanium oxypnictides an important new material system to understand the nature of nematic order and its relationship to superconductivity.