Papers by Dipak Bhattarai
Bibechana, Nov 29, 2023
The transition from trivial to non-trivial phase in two-dimensional materials are called a topolo... more The transition from trivial to non-trivial phase in two-dimensional materials are called a topological phase transition (TPT). The Berry phase, non-local string order parameter, and edge states define the topological nature of the system. A newly discovered jacutingaite material Pt 2 HgSe 3 is a layered material which occurs naturally in the form of minerals. The material can be exfoliated and was predicted as a quantum spin Hall insulator. Here, on the basis of density functional theory and tight-binding calculations, we explore Pt 2 Hg 1-x Tl x Se 3 (x = 0.25, 0.50, 0.75, 1) to understand the electronic and topological properties. We start with the parent material Pt 2 HgSe 3 wherein Hg is replaced partially with x amount of Tl, to tune the topological phases. From the electronic structure calculations, Pt 2 HgSe 3 is found to be a non-trivial semimetal in it's bulk. Upon electron doping, the material transforms to strong topological metallic phase. The topological Z 2 invariant calculation shows TPT in Pt 2 Hg 1-x Tl x Se 3 with weak topological insulating state (0;001) for x=0, to strong topological metal (1;000) for x=1, respectively.
npj Quantum Materials
Interplay of magnetism and electronic band topology in unconventional magnets enables the creatio... more Interplay of magnetism and electronic band topology in unconventional magnets enables the creation and fine control of novel electronic phenomena. In this work, we use scanning tunneling microscopy and spectroscopy to study thin films of a prototypical kagome magnet Fe3Sn2. Our experiments reveal an unusually large number of densely-spaced spectroscopic features straddling the Fermi level. These are consistent with signatures of low-energy Weyl fermions and associated topological Fermi arc surface states predicted by theory. By measuring their response as a function of magnetic field, we discover a pronounced evolution in energy tied to the magnetization direction. Electron scattering and interference imaging further demonstrates the tunable nature of a subset of related electronic states. Our experiments provide a direct visualization of how in-situ spin reorientation drives changes in the electronic density of states of the Weyl fermion band structure. Combined with previous repor...
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Papers by Dipak Bhattarai