Observation of a flat and extended surface state in a topological semimetal

Abstract

A topological flatband, also known as drumhead states, is an ideal platform to drive new exotic topological quantum phases. Using angle-resolved photoemission spectroscopy experiments, we reveal the emergence of a highly localized possible drumhead surface state in a topological semimetal BaAl4 and provide its full energy and momentum space topology. We find that the observed surface state is highly localized in momentum, inside a square-shaped bulk Dirac nodal loop, and in energy, leading to a flat band and a peak in the density of state. These results establish this class of materials as a possible experimental realization of drumhead surface states and provide an important reference for future studies of fundamental physics of topological quantum phase transition.

References in corpus (10)

• Quantum ESPRESSO: a modular and open-source software project for quantum simulations of materials
• High-temperature superconductivity in iron-based materials
• High temperature fractional quantum Hall states
• Fractional quantum Hall states at zero magnetic field
• Nearly-flat bands with nontrivial topology
• Room temperature magnetic order on zigzag edges of narrow graphene nanoribbons
• Flat bands and Wigner crystallization in the honeycomb optical lattice
• Bose condensation in flat bands
• Strain-induced partially flat band, helical snake states, and interface superconductivity in topological crystalline insulators
• Topological surface superconductivity in doped Weyl loop materials

Cited by in corpus (2)

• Non-centrosymmetric, transverse structural modulation in SrAl4, and elucidation of its origin in the BaAl4 family of compounds
• Tuning Incommensurate Charge Order in Ba${}_{1-x}$Sr${}_x$Al${}_4$ and Ba${}_{1-y}$Eu${}_y$Al${}_4$