Controlled alignment of supermoiré lattice in double-aligned graphene heterostructures.

The supermoiré lattice, built by stacking two moiré patterns, provides a platform for creating flat mini-bands and studying electron correlations. An ultimate challenge in assembling a graphene supermoiré lattice is in the deterministic control of its rotational alignment, which is made highly aleatory due to the random nature of the edge chirality and crystal symmetry. Employing the so-called "golden rule of three", here we present an experimental strategy to overcome this challenge and realize the controlled alignment of double-aligned hBN/graphene/hBN supermoiré lattice, where the twist angles between graphene and top/bottom hBN are both close to zero.

Active Ultrahigh-Q (0.2 × 10 ) THz Topological Cavities on a Chip.

Rapid scaling of semiconductor devices has led to an increase in the number of processor cores and integrated functionalities onto a single chip to support the growing demands of high-speed and large-volume consumer electronics. To meet this burgeoning demand, an improved interconnect capacity in terms of bandwidth density and active tunability is required for enhanced throughput and energy efficiency. Low-loss terahertz silicon interconnects with larger bandwidth offer a solution for the existing inter-/intrachip bandwidth density and energy-efficiency bottleneck.

Electrically pumped topological laser with valley edge modes.

Quantum cascade lasers are compact, electrically pumped light sources in the technologically important mid-infrared and terahertz region of the electromagnetic spectrum. Recently, the concept of topology has been expanded from condensed matter physics into photonics, giving rise to a new type of lasing using topologically protected photonic modes that can efficiently bypass corners and defects. Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime.

Fermi-Arc-Induced Vortex Structure in Weyl Beam Shifts.

In periodic media, despite the close relationship between geometrical effects in the bulk and topological surface states, the two are typically probed separately. We show that when beams in a Weyl medium reflect off an interface with a gapped medium, the trajectory is influenced by both bulk geometrical effects and the Fermi arc surface states. The reflected beam experiences a displacement, analogous to the Goos-Hänchen or Imbert-Fedorov shifts, that forms a half-vortex in the two-dimensional surface momentum space.