Quasi-one-dimensional trichalcogenides

MX₃: TiS₃, ZrS₃, ZrTe₃, NbS₃, NbSe₃, TaSe₃; the chain compound (TaSe₄)₂I

Also called TiS₃, ZrS₃, ZrTe₃, NbSe₃, TaSe₃, transition-metal trichalcogenides, MX₃ chain compounds

van der Waals crystal depends on form

Layered crystals whose electrons and light care about direction. Inside each layer the atoms line up in chains, so conduction, absorption and emission differ strongly along and across them – a 2D sheet with a built-in 1D grain. In metallic NbSe₃, electrons below 145 K form a charge-density wave that, above a threshold electric field, slides through the crystal and carries current collectively – one of the classic phenomena of condensed-matter physics. TiS₃ is a semiconductor with a gap close to silicon’s that tells light polarisations apart, and hBN-capped TaSe₃ wires survive current densities an order of magnitude beyond copper’s breakdown limit.

Cell: Rectangular, a = 4.95 Å (across chains), b = 3.38 Å (along chains)
Atoms per cell: 8
Ti–S bonds: 2.44–2.64 Å
S–S bond: 2.12 Å
Height: 5.67 Å between the outer atom centres

Titanium sits in trigonal prisms of sulfur that share faces and run as chains along one direction; neighbouring chains join more loosely to make the layer. Two of the three sulfur atoms in each formula unit are bonded to each other as a disulfide pair, 2.12 Å apart, so TiS₃ is really titanium with one S²⁻ ion and one S₂²⁻ pair. The chains make the layer strongly anisotropic, both electrically and optically. One layer of bulk TiS₃ (Lipatov and colleagues, Nanoscale 7, 12291, 2015; COD 1520546): a = 4.95 Å across the chains, b = 3.38 Å along them, S–S 2.12 Å.

Data sheet

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Kind of sheet: van der Waals crystal
Peels off a layered crystal, one sheet at a time
Behaves as: depends on form
Band gap: TiS₃: ~1 eV, an n-type semiconductor; ZrS₃: ~2 eV, with strongly polarised emission. NbSe₃ and TaSe₃ are metals, and ZrTe₃ is a metal with a charge-density wave

In colour: this family, 1–2 eV. In grey: the other 39 families on the catalogue’s chart, each at the middle of its range.
Thickness: ~0.9 nm per TiS₃ layer
Structure: Chains of face-sharing MX₆ trigonal prisms run along one in-plane axis; neighbouring chains bond more weakly into layers, and the layers stack by van der Waals forces (monoclinic, P2₁/m). NbSe₃ has three distinct types of chain in one cell
Space group: TiS₃: bulk P2₁/m, monolayer Pmmn
ZrS₃: bulk P2₁/m, monolayer Pmmn
NbSe₃: bulk P2₁/m, monolayer P2₁/m
Bulk: the Materials Project crystal linked below. Monolayer: the 2DMatPedia layer, as a periodic slab
Stability: TiS₃ tolerates ambient handling and atomic-layer deposition of alumina, which even improves its transistors. Thin metallic wires are sensitive to surface oxidation, so NbSe₃ and TaSe₃ devices are usually capped with hBN.
First made: Charge-density-wave sliding with a threshold field in NbSe₃ reported in 1979 (Fleming and Grimes); few-layer TiS₃ transistors in 2014–2015 (Island and colleagues; Lipatov and colleagues)
Materials Project: TiS₃
ZrS₃
NbSe₃
Computed crystal structure and properties
2DMatPedia: TiS₃
ZrS₃
NbSe₃
Computed monolayer, exfoliated from a bulk crystal of the same compound

Compare with other materials

Key properties

NbSe₃: two independent charge-density waves, at 145 K and 59 K, yet the crystal stays metallic
Above a threshold electric field the NbSe₃ charge-density wave depins and slides, giving nonlinear conduction and a characteristic conduction noise
TiS₃: ~1 eV gap, n-type field-effect mobilities of ~20–40 cm² V⁻¹ s⁻¹ in few-layer transistors, and an in-plane mobility anisotropy of up to ~8 at low temperature
TiS₃ flakes show linear dichroism with transmission ratios up to 30, larger than in other anisotropic 2D materials
ZrS₃: photoluminescence strongly polarised along the chains
TaSe₃: hBN-capped nanowires carry more than 10 MA cm⁻² before breaking down; ZrTe₃ combines a charge-density wave with superconductivity at a few kelvin
(TaSe₄)₂I, built from the same kind of chains, hosts a charge-density wave in a Weyl semimetal whose sliding mode is argued to behave as an axion

How it is made

TiS₃: millimetre-long whiskers and ribbons by direct reaction of titanium with sulfur, with no transport agent
NbSe₃ nanowires and ribbons by direct reaction of the elements; ZrTe₃ and TaSe₃ crystals by chemical vapour transport
Mechanical exfoliation into ribbons and flakes – down to a single layer for TiS₃ nanosheets – with hBN capping for transport

Uses, and how close they are

Polarisation-sensitive photodetectors (TiS₃, ZrS₃)lab
Anisotropic field-effect transistors (TiS₃)lab
Downscaled local interconnects from quasi-1D metal wires (TaSe₃)lab
Charge-density-wave oscillators and nonlinear devices (NbSe₃)lab

Readiness runs lab → prototype → pilot → deployed.

Open problems

How do the charge-density waves of NbSe₃ and ZrTe₃ change when crystals are thinned to a few chains or a single layer, and does sliding survive?
Does TiS₃ form a charge-density wave or undergo a metal–insulator transition at low temperature? The same transistor data have been read both ways
Can measured TiS₃ mobilities approach the ~10,000 cm² V⁻¹ s⁻¹ predicted along the chains of a monolayer, when today’s values are more than a hundred times lower?
Can quasi-1D metal wires be grown in place, at back-end-of-line temperatures, and tested as interconnects below the size where copper fails?

Going deeper

Short notes for specialists. Choose a lens in the header and yours comes first.

For theoreticians · your lens

Chains make the Fermi surfaces of the metallic members nearly one-dimensional and prone to nesting, so NbSe₃ develops charge-density waves at two wavevectors on different chain types while ungapped pockets keep it metallic. Sliding is the problem of an elastic condensate pinned by impurities – the Fukuyama–Lee–Rice picture – and threshold fields grow as samples shrink. For monolayer TiS₃, DFT predicts a direct gap near 1 eV and an electron mobility along the chains about a hundred times the hole mobility, but such estimates leave out the low-energy polar optical phonons that transport experiments point to. DFT also places TaSe₃ in a strong topological insulator phase, next to its long-known superconductivity.

For experimentalists · your lens

Find the chain axis first: ribbons grow and cleave along it, and angle-resolved polarised Raman confirms it. Measure along and across the chains separately, because averaged values hide the physics. For charge-density-wave transport, look for a sharp threshold field and conduction noise, keep current contacts well away from the voltage probes, and watch for Joule heating near threshold. Thin wires of the metallic members need hBN capping.

For engineers · your lens

Mostly research materials. TiS₃ is closest to a device material, with a ~1 eV gap, compatibility with atomic-layer-deposited dielectrics and strong dichroism for polarisation-sensitive imaging, though its mobility is modest. TaSe₃ wires are studied as local interconnects because they have no grain boundaries and survive current densities that destroy copper. None of these compounds has scalable growth yet.

In the research tracks

Theory frontiers

Electron–phonon coupling and intrinsic mobility

Growth methods

Chemical vapour transport (CVT)

Recent news

The newest items tagged TiS₃, ZrTe₃, NbSe₃, TaSe₃, from the news feed updated 5 Oct 2026.

Preprintnot yet peer reviewed 30 Sep 2026 arXiv

Facet- and thickness-dependent band-edge alignment at ZrSe\texorpdfstring{₃}{3} surfaces: hybrid-functional calculations with spin-orbit coupling

Transition-metal trichalcogenides MX₃ are quasi-one-dimensional van der Waals materials whose layers form through lateral chain binding, giving them an interlayer cleavage plane and in-plane electronic anisotropy. Among them, ZrSe₃ is stable under ambient conditions and semiconducting. Exfoliated crystals expose four…

TheoryTiS₃, ZrTe₃, NbSe₃, TaSe₃

Preprintnot yet peer reviewed 8 Sep 2026 arXiv

Tuning Charge Density Wave transitions through lattice strain in NbSe3

The Charge Density Wave (CDW) state is a perfect example of a combined structural and electronic state, both characterized by a periodic lattice distortion and an electronic modulation of condensed electrons, resulting from electron-phonon coupling. They are thus prone to be tuned by lattice strain. NbSe3 is a…

TheoryExperimentTiS₃, ZrTe₃, NbSe₃, TaSe₃

Preprintnot yet peer reviewed 10 Jun 2026 arXiv

Multiband Superconductivity and Charge Density Wave in HfxZr1-xTe3 single crystals

We report on the bulk multiband superconductivity and charge density wave (CDW) in HfxZr1-xTe3 single crystals. The parent compound ZrTe3 is a layered van der Waals material that undergoes a CDW transition near 63 K and exhibits only filamentary superconductivity below 2.0 K. Upon the introduction of a small amount of…

TheoryTiS₃, ZrTe₃, NbSe₃, TaSe₃

Preprintnot yet peer reviewed 24 Mar 2026 arXiv

Comment on 'Observation of Shapiro Steps in the Charge Density Wave State Induced by Strain on a Piezoelectric Substrate'

In their Letter Fujiwara et al. (10.48550/arXiv.2511.09888. 2025) report a high-quality experiment demonstrating the synchronization of the CDW sliding in NbSe3 whiskers (nanowires) with surface acoustic waves (SAWs). The SAWs are induced in the conventional LiNbO3 piezoelectric substrates through application of rf…

ExperimentTiS₃, ZrTe₃, NbSe₃, TaSe₃

Preprintnot yet peer reviewed 3 Feb 2026 arXiv

Synthesis and guided assembly of niobium trisulfide nanowires and nanowire chains by chemical vapor deposition

One-dimensional (1D) nanostructures of transition metal trichalcogenides (TMT) show unique properties through the combination of their anisotropic bonding and low dimensionality. Scalable synthesis approaches that enable control over the morphology, dimensions, and interfaces of 1D TMTs with other nanoscale materials…

ExperimentTiS₃, ZrTe₃, NbSe₃, TaSe₃ Graphene CrSBr

All 7 items tagged TiS₃, ZrTe₃, NbSe₃, TaSe₃ in the news feed · RSS feed for TiS₃, ZrTe₃, NbSe₃, TaSe₃

Key references

Charge-density waves in NbSe₃ at 145K: crystal structures, X-ray and electron diffraction studiesHodeau et al. · Journal of Physics C 11, 4117 (1978)cited by 180doi:10.1088/0022-3719/11/20/009
Sliding-mode conductivity in NbSe₃: observation of a threshold electric field and conduction noiseFleming & Grimes · Physical Review Letters 42, 1423 (1979)cited by 468doi:10.1103/PhysRevLett.42.1423
The dynamics of charge-density wavesGrüner · Reviews of Modern Physics 60, 1129 (1988)cited by 2,192doi:10.1103/RevModPhys.60.1129
Few-layered titanium trisulfide (TiS₃) field-effect transistorsLipatov et al. · Nanoscale 7, 12291 (2015)cited by 133doi:10.1039/C5NR01895A
Titanium trisulfide monolayer: theoretical prediction of a new direct-gap semiconductor with high and anisotropic carrier mobilityDai & Zeng · Angewandte Chemie International Edition 54, 7572 (2015)cited by 297doi:10.1002/anie.201502107
Titanium trisulfide (TiS₃): a 2D semiconductor with quasi-1D optical and electronic propertiesIsland et al. · Scientific Reports 6, 22214 (2016)cited by 141doi:10.1038/srep22214
Strong dichroic emission in the pseudo one dimensional material ZrS₃Pant et al. · Nanoscale 8, 16259 (2016)cited by 76doi:10.1039/C6NR05238J
Breakdown current density in h-BN-capped quasi-1D TaSe₃ metallic nanowires: prospects of interconnect applicationsStolyarov et al. · Nanoscale 8, 15774 (2016)cited by 117doi:10.1039/C6NR03469A
One-dimensional van der Waals quantum materialsBalandin et al. · Materials Today 55, 74 (2022)cited by 187doi:10.1016/j.mattod.2022.03.015
Axionic charge-density wave in the Weyl semimetal (TaSe₄)2IGooth et al. · Nature 575, 315 (2019)cited by 245doi:10.1038/s41586-019-1630-4