Engineering topics

Addison, Zachariah

Publications and source records attributed to Addison, Zachariah.

3 records

DOE OSTI2020

Nonlinear time-domain spectroscopy near a band inversion

We develop a theory for the nonlinear time-domain response of a semimetal driven by an ultrafast optical pulse. At quadratic order in the driving field we find that the response near a band inversion transition contains a coherent oscillating component proportional to field intensity with a frequency that can be tuned over a wide range (from terahertz to the near IR) selected by the chemical potential. Finally, we illustrate the effect by calculating the induced current as a function of time for a two-band system with time-reversal symmetry but broken parity symmetry to study semimetals where large Berry curvature near a band inversion transition promotes this nonlinear response.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2020

Quadrupole topological photonic crystals

Quadrupole topological phases, exhibiting protected boundary states that are themselves topological insulators of lower dimensions, have recently been of great interest. Extensions of these ideas from current tight binding models to continuum theories for realistic materials require the identification of quantized invariants describing the bulk quadrupole order. Here we identify the analog of quadrupole order in Maxwell’s equations for a gyromagnetic photonic crystal (PhC) through a double-band-inversion process. The quadrupole moment is quantized by the simultaneous presence of crystalline symmetry and broken time-reversal symmetry, which is confirmed using three independent methods: analysis of symmetry eigenvalues, numerical calculations of the nested Wannier bands and the expectation value of the quadrupole operator. Furthermore, we reveal the boundary manifestations of quadrupole phases as quantized edge polarizations and fractional corner charges. The latter are the consequence of a filling anomaly of energy bands as first predicted in electronic systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2019

Optically Controlled Orbitronics on a Triangular Lattice

The propagation of electrons in an orbital multiplet dispersing on a lattice can support anomalous transport phenomena deriving from an orbitally induced Berry curvature. In striking contrast to the related situation in graphene, we find that anomalous transport for an L = 1 multiplet on the primitive 2D triangular lattice is activated by easily implemented on site and optically tunable potentials. Further, we demonstrate this for dynamics in a Bloch band where point degeneracies carrying opposite winding numbers are generically offset in energy, allowing both an anomalous charge Hall conductance with the sign selected by off-resonance coupling to circularly polarized light and a related anomalous orbital Hall conductance activated by layer buckling.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗