Topological magnons driven by the Dzyaloshinskii-Moriya interaction in the centrosymmetric ferromagnet MnGe.

The phase of the quantum-mechanical wave function can encode a topological structure with wide-ranging physical consequences, such as anomalous transport effects and the existence of edge states robust against perturbations. While this has been exhaustively demonstrated for electrons, properties associated with the elementary quasiparticles in magnetic materials are still underexplored. Here, we show theoretically and via inelastic neutron scattering experiments that the bulk ferromagnet MnGe hosts gapped topological Dirac magnons.

Unconventional short-range structural fluctuations in cuprate superconductors.

The interplay between structural and electronic degrees of freedom in complex materials is the subject of extensive debate in physics and materials science. Particularly interesting questions pertain to the nature and extent of pre-transitional short-range order in diverse systems ranging from shape-memory alloys to unconventional superconductors, and how this microstructure affects macroscopic properties. Here we use neutron and X-ray diffuse scattering to uncover universal structural fluctuations in LaSrCuO and TlBaCuO, two cuprate superconductors with distinct point disorder effects and with optimal superconducting transition temperatures that differ by more than a factor of two.

Doping- and Strain-Dependent Electrolyte-Gate-Induced Perovskite to Brownmillerite Transformation in Epitaxial LaSrCoO Films.

Much recent attention has focused on the voltage-driven reversible topotactic transformation between the ferromagnetic metallic perovskite (P) SrCoO and oxygen-vacancy-ordered antiferromagnetic insulating brownmillerite (BM) SrCoO. This is emerging as a paradigmatic example of the power of electrochemical gating (using, , ionic liquids/gels), the wide modulation of electronic, magnetic, and optical properties generating clear application potential. SrCoO films are challenging with respect to stability, however, and there has been little exploration of alternate compositions.

Spin Fluctuations Drive the Inverse Magnetocaloric Effect in Mn_{5}Si_{3}.

Inelastic neutron scattering measurements are performed on single crystals of the antiferromagnetic compound Mn_{5}Si_{3} in order to investigate the relation between the spin dynamics and the magnetothermodynamics properties. It is shown that, among the two stable antiferromagnetic phases of this compound, the high temperature one has an unusual magnetic excitation spectrum where propagative spin waves and diffuse spin fluctuations coexist. Moreover, it is evidenced that the inverse magnetocaloric effect of Mn_{5}Si_{3}, the cooling by adiabatic magnetization, is associated with field induced spin fluctuations.