Skip to main content

ALS

Home / News / Science Briefs / Crossing from One to Two Dimensions in a Single Material

Crossing from One to Two Dimensions in a Single Material

Low-dimensional (1D or 2D) materials often exhibit fascinating emergent physics that make them candidates for next-generation electronic devices. Despite this, the realization of low-dimensional electronic states that are tunable—which is useful for experimentation—appears to be rare. Now, researchers have discovered that a family of layered compounds offers an ideal platform for tuning between 1D and 2D physics.

“Different dimensional systems have different phenomena, and it’s important to know how a system evolves from one to the other and how each system’s uniqueness disappears,” said study co-author Yulin Chen of ShanghaiTech University and the University of Oxford. “But it’s typically pretty hard. For example, if you want to study a 1D system, you go to a nanowire system; if you want to study a 2D system, you need to grow 2D films. But then they’re apples and oranges, different systems. This system is cleaner. It’s the same material essentially, and you just tweak the electronic interactions.”

The material in question is NbSixTe2, which previous studies have shown to contain 1D metallic chains of NbTe2. By changing the silicon content (values of x) during synthesis, the spacing between chains can be altered.

To investigate the 1D nature of the metallic chains as well as their evolution with different x values, the researchers used angle-resolved photoemission spectroscopy (ARPES) at Advanced Light Source Beamline 10.0.1. The data showed that, as the Si content decreased (from x = 0.43 to x = 0.40) and the chains were brought closer together, interactions between the chains increased.

“The physical scenario is that the electrons are traveling fast along these metallic chains. But because of the smaller distances, the electrons are able to hop between chains,” said co-author Zhongkai Liu of ShanghaiTech University. “These interactions transform the 1D structures into 2D, and you can see these changes reflected in the ARPES data.”

Thus, with this system, scientists will be able to study how 1D and 2D states evolve from one another. The ability to tune and control two very different yet important phenomena expands possibilities for device engineering, and more generally, offers a versatile platform for the exploration of intriguing low-dimensional physics.

Comparison of 1D and 2D cases: crystal structures (left), schematic band shapes (center), and ARPES data (right).
Left: Crystal structure of NbSixTe2. The distance between chains (red rows) is smaller for smaller values of x. Center: Schematic of ARPES features for systems with and without dimensional crossover. Cuts through the planes at various points (labeled S and X) would not change for a 1D system (top). Similar cuts in the 2D case would show variations in the band slopes (bottom). Right: ARPES data show no change in the band slopes (crossed red lines) for the 1D case, but a clear difference is seen for the 2D case.

J. Zhang, Y. Lv, X. Feng, A. Liang, W. Xia, S.-K. Mo, C. Chen, J. Xue, S.A. Yang, L. Yang, Y. Guo, Y. Chen, Y. Chen, and Z. Liu, “Observation of dimension-crossover of a tunable 1D Dirac fermion in topological semimetal NbSixTe2,” npj Quantum Mater. 7, 54 (2022), doi:10.1038/s41535-022-00462-6.