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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Recently discovered intrinsic antiferromagnetic topological insulatorMnBi$_2$Te$_4$ presents an exciting platform for realization of the quantumanomalous Hall effect and a number of related phenomena at elevatedtemperatures. An important characteristic making this material attractive forapplications is its predicted large magnetic gap at the Dirac point (DP).However, while the early experimental measurements reported on large DP gaps, anumber of recent studies claimed to observe a gapless dispersion of theMnBi$_2$Te$_4$ Dirac cone. Here, using micro($\mu$)-laser angle-resolvedphotoemission spectroscopy, we study the electronic structure of 15 differentMnBi$_2$Te$_4$ samples, grown by two different chemists groups. Based on thecareful energy distribution curves analysis, the DP gaps between 15 and 65 meVare observed, as measured below the N\'eel temperature at about 10-16 K. Atthat, roughly half of the studied samples show the DP gap of about 30 meV,while for a quarter of the samples the gaps are in the 50 to 60 meV range.Summarizing the results of both our and other groups, in the currentlyavailable MnBi$_2$Te$_4$ samples the DP gap can acquire an arbitrary valuebetween a few and several tens of meV. Further, based on the density functionaltheory, we discuss a possible factor that might contribute to the reduction ofthe DP gap size, which is the excess surface charge that can appear due tovarious defects in surface region. We demonstrate that the DP gap is influencedby the applied surface charge and even can be closed, which can be takenadvantage of to tune the MnBi$_2$Te$_4$ DP gap size.

Sample-dependent Dirac point gap in MnBi$_2$Te$_4$ and its response to the applied surface charge: a combined photoemission and ab initio study