Stanene is a topological insulator made up of atoms typically arranged in a similar pattern to those in graphene. Stanene films have shown promise for the realization of numerous intriguing physics phases, including the quantum spin Hall phase and intrinsic superconductivity.
Some theoretical studies also suggested that these films are topological superconductivity, a state particularly valuable for the development of quantum computing technology. Until now, however, topological edge states in stanene have not been reliably and consistently observed in experimental settings.
Researchers from Shanghai Jiao Tong University, University of Science and Technology of China, Henan University, Zhengzhou University and other institutes in China recently demonstrated the coexistence of topological edge states and superconductivity in stanene films from one to five layers that are on the Bi (111) substrate† Their observations, set forth in a paper published in Physical Assessment Letterscould have important implications for the development of Stanene-based quantum devices.
“The current work is a final step forward in our systematic review after our previous work published in 2015, which represented the first report on the successful growth of a stanene monoatomic layer (ML),” Jinfeng Jia, one of the researchers who the study, told Phys.org. “The challenge at the time was the Bi2At3 substrate places a compressive stress on the stanene layer, leading to an unfavorable overlap between the conduction and valence bands.”
Building on previous findings, Jia’s team and other research groups around the world have been trying to realize topological superconductivity placed in stanene on different substrates with greater lattice constraints than Bi2At3, as these might preserve the non-trivial topology of stanene. But so far few had succeeded.
To build efficient quantum computing technologies based on stanene films, physicists will first need to identify a substrate that can be used to grow stably stanene with nontrivial topological properties and intrinsic superconductivity. Here’s what Jia and his colleagues set out to do in their recent paper.
“The ultimate goal of our recent paper is to achieve the topological superconductor in stanene, a single-element material system,” Jia said. “Such a desirable substrate was identified by our more recent theoretical study, pointing to the Bi(111) substrate.”
In their experiments, Jia and his colleagues collected measurements using scanning tunneling microscopy and spectroscopy at an ultra-low temperature of 400 mK. These methods allowed them to detect localized topological edge states on their nanometer-scale stanene samples and confirm the superconducting pairing in the material.
“Our first principle calculations further confirmed the nontrivial topology of those films, and the vital importance of significant spin-orbital coupling through the Bi(111) substrate,” Jia explained. “We have also shown that hydrogen is indispensable to adapt the growth habit to grow smoothly and layer by layer.”
The recent work of this team of researchers conclusively demonstrates the coexistence of topological edge states and superconductivity in standard films. Unlike other previous realizations of these states, these two properties are sampled in a single element system, rather than in a complicated heterostructure.
The short bilateral penetration lengths of the edge states observed by Jia and colleagues are particularly beneficial for the development of low loss conductive devices with dense edge channels. In addition, the stanene film platform identified by the researchers could enable the development of topological quantum computing devices based on fewer stanene layers.
“For the stanene/Bi(111) system, the next step is to identify the pairing symmetry of its superconductivity and realize Majorana null modes by creating boundaries for the closed-loop edge channel,” Jia added. “The long-term goal of our group is to realize the interlacing of the Majorana modes and even move on to topological quantum computers.”
Chenxiao Zhao et al, Coexistence of robust edge states and superconductivity in low-layer Stanene, Physical Assessment Letters (2022). DOI: 10.1103/PhysRevLett.128.206802
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Quote: Study observes the coexistence of topological edge states and superconductivity in stanene films (2022, June 16) retrieved June 20, 2022 from https://phys.org/news/2022-06-coexistence-topological-edge-states- superconductivity.html
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