Abstract

Topological insulators are insulators in the bulk but permit spin-polarized electrons to flow on their surface. Till date, non-magnetic topological materials have been extensively studied. However, due to the complex symmetries of magnetic crystals as well as theoretical and experimental difficulties associated with modeling and measuring quantum magnets, only a few magnetic materials have been explored so far. Therefore, by utilizing angle-resolved photoemission spectroscopy (ARPES), along with first-principles calculations, and magneto-transport measurements, we have chosen one doped and four intrinsic magnetic materials to study the interplay between magnetic order and nontrivial topology. First, we have observed a single topological non-trivial surface state in a spin-orbit-induced bulk bandgap magnetic material (Gd doped Sb2Te3), where the surface states are possibly associated with the 4f -electron magnetism of gadolinium. Our subsequent research has focused on an intrinsic magnetic quantum material, EuMg2Bi2, which reveals multiple Dirac states, with the Dirac nodes located at distinct binding energies. Next, we have investigated kagome-net magnets, due to the unusual lattice geometry and breaking of time-reversal symmetry, they can support diverse quantum magnetic phases. We have studied HoMn6Sn6 and ErMn6Sn6 kagome net magnets, which revealed large anomalous, topological Hall effects, and Dirac-like dispersions near the Fermi level indicating the existence of a Chern gapped Dirac cone. Finally, numerous fascinating topological phases of rare-earth monopnictide (REM) family led us to investigate the electronic structure of another REM magnetic topological material NdSb, which revealed significant band reconstruction due to the onset of an antiferromagnetic transition. Our results reveal a linear Dirac-like state at the zone center and two Dirac-like states at the zone corner of the Brillouin zone, indicating non-trivial topology in this material. Our detailed electronic structure study of these 4f magnetic materials could potentially provide a foundation for future research investigating the interaction between topology and magnetism.

Notes

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Graduation Date

2021

Semester

Fall

Advisor

Neupane, Madhab

Degree

Doctor of Philosophy (Ph.D.)

College

College of Sciences

Department

Physics

Degree Program

Physics

Format

application/pdf

Identifier

CFE0008857

Language

English

Release Date

December 2022

Length of Campus-only Access

1 year

Access Status

Doctoral Dissertation (Campus-only Access)

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