A Punch line: altermagnetism

This is the first version of the editorial foreword to the Perspective review "Research Landscape of Altermagnetism" by L. \v{S}mejkal, et al, published in Phys. Rev. X 12, 040501 (2022). Due to various editorial constraints the publish version (DOI:10.1103/PhysRevX.12.040002) deviates substantially from the initial text. This posting intends to make this original version available for perusal of potential readers

Ising superconductivity: a first-principles perspective

The recent discovery of Ising superconductivity has garnered a lot of interest due in part to the resilience of these superconductors to large in-plane magnetic fields. In this Perspective we explain the basic concepts that define the behavior of Ising superconductors, provide an overview of the electronic structure and magnetic properties with a focus on NbSe$_2$, summarize key experimental observations that have been made in this class of superconductors, highlight the role that defects and proximity-induced effects at interfaces have on Ising superconductivity and finally discuss the prospects for observing Ising superconductivity in bulk materials.Comment: 10 pages, 8 figure

Superconductivity in La₂Ni₂In

We report here the properties of single crystals of La2Ni2In. Electrical resistivity and specific heat measurements concur with the results of density functional theory calculations, finding that La2Ni2In is a weakly correlated metal, where the Ni magnetism is almost completely quenched, leaving only a weak Stoner enhancement of the density of states. Superconductivity is observed at temperatures below 0.9 K. A detailed analysis of the field and temperature dependencies of the resistivity, magnetic susceptibility, and specific heat at the lowest temperatures reveals that La2Ni2In is a dirty type-II superconductor with likely s-wave gap symmetry. Nanoclusters of ferromagnetic inclusions significantly affect the subgap states resulting in a nonexponential temperature dependence of the specific heat C(T) at T ≪ Tc

CrRhAs: a member of a large family of metallic kagome antiferromagnets

Kagome lattice materials are an important platform for highly frustrated magnetism as well as for a plethora of phenomena resulting from flat bands, Dirac cones and van Hove singularities in their electronic structures. We study the little known metallic magnet CrRhAs, which belongs to a vast family of materials that include $3d$, $4f$ and $5f$ magnetic elements, as well as numerous nonmagnetic metals and insulators. Using noncollinear spin density functional calculations (mostly spin spirals), we extract a model magnetic Hamiltonian for CrRhAs. While it is dominated by an antiferromagnetic second nearest neighbor coupling in the kagome plane, the metallic nature of the compound leads to numerous nonzero longer range couplings and to important ring exchange terms. We analyze this Hamiltonian and find unusual ground states which are dominated by nearly isolated antiferromagnetic triangles that adopt 120$^\circ$ order either with positive or with negative vector chirality. We discuss the connection to the few known experimental facts about CrRhAs. Finally, we give a brief survey of other interesting magnetic members of this family of kagome compounds.Comment: 16 page

Vitaly Ginzburg and High Temperature Superconductivity: Personal Reminiscences

I offer some personal reminiscences from the period of 1976-1983, when I was a M. Sc. and then a Ph.D. student in Vitaly L. Ginzburg's High Temperature Superconductivity group at the P.N. Lebedev Institute in MoscowComment: To be published in proceedings of the Notre Dame Workshop on the Possibility of Room Temperature Superconductivity, June 2005 v.2: an apposite epigraph adde