Topological Transition of Dirac Points in a Microwave Experiment

Abstract

By means of a microwave tight-binding analogue experiment of a graphene-like lattice, we observe a topological transition between a phase with a point-like band gap characteristic of massless Dirac fermions and a gapped phase. By applying a controlled anisotropy on the structure, we investigate the transition directly via density of states measurements. The wave function associated with each eigenvalue is mapped and reveals new states at the Dirac point, localized on the armchair edges. We find that with increasing anisotropy, these new states are more and more localized at the edges.

Artificial honeycomb lattices for electrons, atoms and photons

“…Close to the Dirac point there appear states at the straight edge of the photonic crystal that represent the artificial counterpart of the states at a zigzag edge of natural graphene. Optical analogues of graphene operating in the microwave frequency range have been recently used to simulate anisotropic honeycomb lattices and to observe topological phase transitions of Dirac points [53].…”

Valley-dependent gauge fields for ultracold atoms in square optical superlattices

“…On the other hand, a growing class of Dirac materials with synthetic honeycomb structure have recently been proposed and explored [8], such as trapped cold atoms in optical lattices (OL) [9,10], confined photons in photonic crystals [11,12], and molecular graphene [13]. Interestingly, the pseudo-magnetic fields and related Landau levels have been experimentally demonstrated in photonic graphene [11] and molecular graphene [13] by designing a spatial texture of hopping parameters.…”

“…It has been show that such gauge fields can be realized by modulating the electronic hopping with strains in a two-dimensional (2D) honeycomb lattice [5,6]. These findings open up an exciting area of mechanically engineering band structure of graphene [3], as well as realizing some exotic phenomena absent in other solid-state materials, such as new types of quantum Hall related effects [4,7].On the other hand, a growing class of Dirac materials with synthetic honeycomb structure have recently been proposed and explored [8], such as trapped cold atoms in optical lattices (OL) [9,10], confined photons in photonic crystals [11,12], and molecular graphene [13]. Interestingly, the pseudo-magnetic fields and related Landau levels have been experimentally demonstrated in photonic graphene [11] and molecular graphene [13] by designing a spatial texture of hopping parameters.…”

Quantum Hall effect in ac driven graphene: From the half-integer to the integer case

“…2(c) 16 . While the physics of Dirac cones merging is originally formulated in the context of graphene, various analog systems [33][34][35] have paved the way to its physical realization including new aspects being addressed 36 . In the following, we will focus on the Hall transport phenomenon.…”