Topic
Topological materials research, explained
11 open-access topological materials studies, each with a flashcard deck and a quiz.
- Can light's frequency act as an extra dimension for topology?
Simulations show that pairs of modulated ring resonators can use light's frequency as an extra dimension to build a higher-order topological insulator whose corner states resist disorder.
- Do topological edge states need a crystal lattice?
Light-guiding one-way edge states, usually thought to need a periodic crystal, survived in a disordered (amorphous) lattice of magnetic rods but disappeared once the lattice lost its local order.
- Can topological insulators triple terahertz frequencies efficiently?
Thin films of topological insulators convert terahertz light to three times its frequency far more efficiently than graphene at high power, reaching about half a milliwatt of output.
- Can topological corner states survive inside the bulk energy band?
Light injected at a corner of a topological photonic lattice stays trapped there even though the corner states share their energy with bulk states, until the bandgap is made too small.
- How do hot electrons change a Weyl semimetal's direction-dependence?
After a laser pulse heats its electrons, the Weyl semimetal TaIrTe4 responds to light more equally in all in-plane directions, the opposite of what happens in black phosphorus.
- Can a passive, static structure show one-way topological effects?
Simply making the two diagonal bars of a lattice unequally stiff lets a motionless, unpowered mechanical metamaterial steer and squeeze deformation toward one edge, a topological effect normally needing active energy input.
- Can light bend the 'wrong' way at every angle with no reflection?
Surface waves on a specially designed topological metamaterial are predicted to bend backwards at a boundary for every incoming angle while reflecting nothing, which could allow a perfect flat lens.
- Can magnetic skyrmions make flat topological bands?
Calculations predict that a semiconductor layer placed on a magnet with skyrmion textures can host an almost perfectly flat band that also carries a topological Chern number.
- Can light absorption reveal the hidden geometry of electron waves?
Calculations show that in a thin magnetic topological insulator, how much light is absorbed encodes the quantum geometry of its electrons, and a three-layer film absorbs one circular polarization almost exclusively.
- Can a topological insulator turn heat into spin current?
A thin film of the topological insulator bismuth selenide turns a temperature gradient into a flow of electron spin far more efficiently than platinum or tungsten.
- Can swapping bismuth for antimony flip a magnet's Hall signals?
Replacing bismuth with antimony in a magnetic topological insulator reverses the sign of both its anomalous Hall signal and its second-harmonic Hall signal, because the band structure's Berry curvature and spin texture change.