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Strong Coupling Between Topological Surface States of Lights

Researchers of the I-Lum team at INL has suggested utilizing a synthetic 1D photonic crystal to achieve Fermi Arc reconstruction of 3D Weyl semimetals. Our system lays the groundwork for exploring physics in higher dimensions, like the 4D quantum Hall effect and 5D Weyl semimetal.

In 1929, Hermann Weyl discovered a massless fermion within the Dirac equation, later termed the Weyl fermion. Almost a century afterward, Weyl fermions have recently been demonstrated in materials known as Weyl semimetals. The topological blueprint of these materials consists of chiral surface states with open Fermi surfaces, known as Fermi arcs. Intriguingly, at the interface of two Weyl semimetals, these Fermi arcs are theorized to hybridize and change their connectivity, featuring an avoided-crossing characteristic. Nonetheless, there isn’t a practical configuration yet for observing Fermi Arc reconstruction.

Recently, the researchers of the I-Lum team at INL suggested utilizing a synthetic photonic crystal to achieve Fermi Arc reconstruction with light. Our design consists of three layers of photonic grating. The relative shifts between neighboring layers act as two synthetic momenta. This configuration mimics 3D crystals without time-reversal symmetry, encompassing Weyl semimetal, nodal line semimetal, and Chern insulator. The phase transition from Weyl semimetal to Chern insulator at telecom wavelengths is nicely demonstrated, with perfect agreement between numerical simulations and analytical theory. Most importantly, we observe for the first time the Fermi Arc reconstruction in a realistic and practical system. Our system lays the groundwork for exploring not just physics in higher dimensions, like the 4D quantum Hall effect and 5D Weyl semimetal, but also novel phases of non-Hermitian topologies. This work is now published in Physical Review Letters.

Contact: Hai-Son NGUYEN

Reference: “Fermi arc reconstruction in synthetic photonic lattice”
D.-H.-Minh Nguyen, Chiara Devescovi, Dung Xuan Nguyen, Hai Son Nguyen, Dario Bercioux
Physical Review Letters 131, 053602 (2023) – https://doi.org/10.1103/PhysRevLett.131.053602

Collaborations: Donostia International Physics Center (San Sebastián, Spain), Center for Theoretical Physics of Complex Systems, Institute for Basic Science (Daejeon, Korea)

Gauche : Trois couches de réseaux photoniques qui imitent le semi-métal de Weyl 3D avec des moments synthétiques. Droite : Le concept de reconstruction des arcs de Fermi.