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SOLID STATE & STRUCTURAL CHEMISTRY UNIT

INDIAN INSTITUTE OF SCIENCE
BANGALORE 12
SPECIAL SEMINAR

By
Dr. Kaustuv Manna
Max Planck Institute for Chemical Physics of Solids
Dresden, Germany
Title
“Discovery of topological magnet and chiral Fermionic systems”
on Tuesday, 3rd September, 2019 at 4.00 PM
Venue : SSCU Auditorium
ALL ARE CORDIALLY INVITED TO ATTEND
CHAIRMAN, SSC
Abstract: 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 [7].

References:

1. K. Manna et al. Phys. Rev. X 8, 041045 (2018).

2. K. Manna et al. Nat. Rev. Mater. 3, 244 (2018).

3. I. Belopolski*, K. Manna* et al. “Discovery of topological Weyl lines and drumhead surface states in a room-temperature magnet”, Science (online around 20.09.2019), *equal contribution.

4. S. N. Guin, K. Manna et al. NPG Asia Mater. 11, 16 (2019).

5. D. S. Sanchez,.. K. Manna et al. Nature 567, 500 (2019).

6. N. Schröter,.. K. Manna et al. Nature Physics (2019).

7. D. Rees, K. Manna et al. arXiv:1902.03230 (2019).

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