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The interplay between topology and various symmetry-breaking phases of matter has emerged as
a key frontier in solid-state physics. This provides a fertile platform to realize the elusive concepts from
particle physics in a condensed matter system. Their topologically protected unusual electronic behavior
carries immense interest for future dissipationless spintronics to other applications. Here I shall discuss
our discovery of a room temperature topological magnet (Co2MnGa), with a topological transport-bulksurface correspondence. The anomalous Hall conductivity attains a colossal value of ~ 1600 Ω
-1
cm-1
at 2
K for Co2MnGa [1-3]. Even at room temperature, we observe the highest anomalous Hall angle upto 12%
and largest anomalous Nernst thermopower of ~6.0 µV K−1
, which is approximately 7 times larger than
any material ever reported in literature [1,4]. Then with experimental proof, I demonstrate how one can
tune the anomalous Hall conductivity in topological magnetic Heusler compounds, via the symmetry
engineering, from a colossal value of ~ 2000 Ω-1
cm-1
to zero without disturbing sample’s magnetization
[1-3]. In the second section, I shall discuss our recent discovery of topological chiral crystals [5,6]. This
novel phase of matter carries many intrinsic ideal and near-ideal properties that emerge as a direct
consequence of the structural chirality of the crystals. I shall illustrate high-quality crystal growth
procedures of various chiral crystals and the controllability of their structural chirality for tuning the
physical properties. For the first time, we have observed room temperature quantized circular
photogalvanic response in a candidate chiral crystal RhSi, which arose significant enthusiasm in the
topological community. |