Also called TaIrTe₄, NbIrTe₄, ZrTe₅, HfTe₅, pentatellurides
Layered crystals where ideas from topology turn into measurable effects, some of them at room temperature. TaIrTe4 is a Weyl semimetal whose low symmetry lets thin flakes rectify radio waves and detect mid-infrared light without any bias, and lets its spin currents flip magnets that point out of the plane without a magnetic field. A single TaIrTe4 layer conducts along its edges in two separate ranges of electron density. ZrTe5 and HfTe5 sit so close to a change of topology that strain can tip them across it, and bulk crystals show Hall plateaus reported as a three-dimensional quantum Hall effect.
Three layers of HfTe5, seen across the chains. Each layer is shifted by half a cell along the chains against the one below, so every second layer lines up: 7.25 Å between layers. Cell from Furuseth, Brattås and Kjekshus, Acta Chemica Scandinavica 27, 2367 (1973); COD 1527386.
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TaIrTe4 is a minimal type-II Weyl semimetal: its four Weyl points are the fewest that time-reversal symmetry allows. Broken inversion and its low Pmn21 symmetry permit a Berry-curvature dipole, which drives the second-order nonlinear Hall response, and out-of-plane spin polarisation in spin–orbit torques. In the monolayer, van Hove singularities reached by modest electron doping make correlations strong enough to open a new gap, inside which helical edges reappear. In ZrTe5 and HfTe5 the gap at Γ is so small that its sign – and with it the topology – changes with the lattice constants, so calculations should start from the measured structure at the temperature of the experiment.
For nonlinear Hall measurements, drive at frequency ω and lock in at 2ω, and rotate the current relative to the crystal axes: a genuine signal follows the crystal symmetry, while thermoelectric and contact artefacts do not. In ZrTe5, negative longitudinal magnetoresistance is easily faked by current jetting, so use several voltage-contact pairs across the sample width. Carrier density and the resistivity-peak temperature differ between vapour-grown and flux-grown crystals; report both before comparing samples.
The appeal is function without cooling: TaIrTe4 rectifies radio frequencies and detects mid-infrared light at room temperature with no bias, and its out-of-plane spins switch perpendicular magnets without the in-plane field that conventional heavy-metal layers need. Every demonstration so far uses exfoliated flakes; wafer-scale growth, the cost of iridium and the scarcity of tellurium stand between them and a product. ZrTe5 and HfTe5 remain research materials.
The newest items tagged TaIrTe4, ZrTe5, HfTe5, from the news feed updated 5 Oct 2026.
Pressure can drive Weyl semimetals toward superconductivity through qualitatively distinct reconstructions of their lattices and normal-state electronic structures. Here, we report the first observation of superconductivity in compressed TaRhTe4. This finding enables a direct comparison of the distinct reconstruction…
The functional quantum spin Hall insulators (QSHI), protected by time-reversal symmetry against single-particle backscattering, hold great promise for dissipationless quantum electronics. Realization of QSHI with gapped helical edge states, which would enable deterministic on/off switching of the edge-channel…
Monolayer ZrTe5 is predicted to host a large-gap quantum spin Hall phase, motivating efforts to isolate single layers of the material. Gold-assisted exfoliation produces clean monolayers of many chalcogen-terminated van der Waals crystals, but the strong Te-Au bond may compete with the bonding network of the ZrTe5…
Recent transport experiments reported a quantum spin Hall insulator phase in monolayer 1T-TaIrTe4 gated away from charge neutrality. This phase is not predicted by band structure calculations and has been attributed to an electronic instability induced by strong correlations at a putative van Hove singularity. Here, we…
Theoretical and experimental mapping of monolayer TaIrTe 4 reveals a rich landscape of interaction-driven topological phases on a single naturally layered crystal—no moiré engineering required. [Phys. Rev. X 16, 031017] Published Fri Jul 24, 2026
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