English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The BaAl$_4$ prototype crystal structure is the most populous of allstructure types, and is the building block for a diverse set of sub-structuresincluding the famous ThCr$_2$Si$_2$ family that hosts high-temperaturesuperconductivity and numerous magnetic and strongly correlated electronsystems. The MA$_4$ family of materials (M=Sr, Ba, Eu; A=Al, Ga, In) themselvespresent an intriguing set of ground states including charge and spin orders,but have largely been considered as uninteresting metals. Using electronicstructure calculations, symmetry analysis and topological quantum chemistrytechniques, we predict the exemplary compound BaAl$_4$ to harbor athree-dimensional Dirac spectrum with non-trivial topology and possible nodallines crossing the Brillouin zone, wherein one pair of semi-Dirac points withlinear dispersion along the $k_z$ direction and quadratic dispersion along the$k_x/k_y$ direction resides on the rotational axis with $C_{4v}$ point groupsymmetry. Electrical transport measurements reveal the presence of an extremelylarge, unsaturating positive magnetoresistance in BaAl$_4$ despite anuncompensated band structure, and quantum oscillations and angle-resolvedphotoemission spectroscopy measurements confirm the predicted multibandsemimetal structure with pockets of Dirac holes and a Van Hove singularity(VHS) remarkably consistent with the theoretical prediction. We thus presentBaAl$_4$ as a new topological semimetal, casting its prototype status into anew role as building block for a vast array of new topological materials.

Crystalline symmetry-protected non-trivial topology in prototype compound BaAl$_4$