# INTERPLAY OF GEOMETRY WITH IMPURITIES AND DEFECTS IN TOPOLOGICAL STATES OF MATTER

The discovery of topological quantum states of matter has required physicists to look beyond Landau’s theory of symmetry-breaking, previously the main paradigm for

studying states of matter. This has led also to the development of new topological theories for describing the novel properties. In this dissertation an investigation in this

frontier research area is presented, which looks at the interplay between the quantum geometry of these states, defects and disorder. After a brief introduction to the topological quantum states of matter considered herein, some aspects of my work in this area are described. First, the disorder-induced band structure engineering of topological insulator surface states is considered, which is possible due to their resilience from Anderson localization, and believed to be a consequence of their topological origin.

Next, the idiosyncratic behavior of these same surface states is considered, as observed in experiments on thin film topological insulators, in response to competition between

hybridization effects and an in-plane magnetic field. Then moving in a very different direction, the uncovering of topological ‘gravitational’ response is explained: the

topologically-protected charge response of two dimensional gapped electronic topological states to a special kind of 0-dimensional boundary – a disclination – that encodes spatial curvature. Finally, an intriguing relation between the gravitational response of quantum Hall states, and their response to an apparently unrelated perturbation – nonuniform electric fields is reported.

studying states of matter. This has led also to the development of new topological theories for describing the novel properties. In this dissertation an investigation in this

frontier research area is presented, which looks at the interplay between the quantum geometry of these states, defects and disorder. After a brief introduction to the topological quantum states of matter considered herein, some aspects of my work in this area are described. First, the disorder-induced band structure engineering of topological insulator surface states is considered, which is possible due to their resilience from Anderson localization, and believed to be a consequence of their topological origin.

Next, the idiosyncratic behavior of these same surface states is considered, as observed in experiments on thin film topological insulators, in response to competition between

hybridization effects and an in-plane magnetic field. Then moving in a very different direction, the uncovering of topological ‘gravitational’ response is explained: the

topologically-protected charge response of two dimensional gapped electronic topological states to a special kind of 0-dimensional boundary – a disclination – that encodes spatial curvature. Finally, an intriguing relation between the gravitational response of quantum Hall states, and their response to an apparently unrelated perturbation – nonuniform electric fields is reported.

## History

## Degree Type

- Doctor of Philosophy

## Department

- Physics and Astronomy

## Campus location

- West Lafayette

## Advisor/Supervisor/Committee Chair

Rudro Biswas## Additional Committee Member 2

Gabor Csathy## Additional Committee Member 3

Chris Greene## Additional Committee Member 4

Michael Manfra## Usage metrics

## Categories

## Keywords

Topological quantum phasesspatial curvaturetopological invarianttopological gravitational responsegauge-invariant variablequantum Halltopological insulatorChern insulatorDirac fermionimpuritytopological defectdisclinationT matrixGreen's functiondisorderCondensed Matter PhysicsComputational PhysicsQuantum MechanicsElectronic and Magnetic Properties of Condensed Matter; SuperconductivityGeneral Relativity

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