# An On/Off Berry Phase Switch in Circular Graphene Resonators

## TL;DR

This paper demonstrates a magnetic-field-controlled Berry phase switch in circular graphene resonators, causing significant energy shifts in angular-momentum states, with potential applications in optoelectronic devices.

## Contribution

It reveals a novel Berry-phase-induced spectroscopic feature in graphene, enabling magnetic control of topological phases for device applications.

## Key findings

- Large energy increase at critical magnetic field due to Berry phase transition
- Berry phase switch can be toggled with small magnetic field changes (~10 mT)
- Topological properties of Dirac fermions enable new optoelectronic functionalities

## Abstract

The phase of a quantum state may not return to its original value after the system's parameters cycle around a closed path; instead, the wavefunction may acquire a measurable phase difference called the Berry phase. Berry phases typically have been accessed through interference experiments. Here, we demonstrate an unusual Berry-phase-induced spectroscopic feature: a sudden and large increase in the energy of angular-momentum states in circular graphene p-n junction resonators when a small critical magnetic field is reached. This behavior results from turning on a $\pi$-Berry phase associated with the topological properties of Dirac fermions in graphene. The Berry phase can be switched on and off with small magnetic field changes on the order of 10 mT, potentially enabling a variety of optoelectronic graphene device applications.

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Source: https://tomesphere.com/paper/1705.11117