A new iron-based superconductor stabilized by inter-block charger transfer

May 16, 2019

Iron-based superconductors (IBSCs) have attracted sustained research attention over the past decade, partly because new IBSCs were discovered one after another in the earlier years. At the time being, however, exploration of IBSCs becomes more and more challenging. A research team from Zhejiang University developed a structural design strategy for the exploration (H. Jiang et al., China Phys. B, 2013, 22:087410), from which they succeeded in finding a series of hole-doped IBSCs with double FeAs layers in recent years. Nevertheless, the electron-doped analogue has not been realized until now.

The newly discovered electron-doped IBSC is BaTh2Fe4As4(N0.7O0.3)2, an intergrowth compound of un-doped BaFe2As2 and electron-doped ThFeAsN0.7O0.3 (see the inset of Figure 1). The new superconductor could be synthesized only when nitrogen is partially replaced with oxygen as in the case of BaTh2Fe4As4(N0.7O0.3)2. Namely, the oxygen-free phase, BaTh2Fe4As4N2, could not be prepared albeit of the lattice matching. The realized synthetic process is actually a redox reaction, BaFe2As2 + 2ThFeAsN0.7O0.3 = BaTh2Fe4As4(N0.7O0.3)2, which indicates an essential role of inter-block charge transfer for stabilizing the intergrowth structure. Note that, while both the constituent structural blocks share identical iron atoms, they contain crystallographically different arsenic atoms, as a consequence of the charge transfer.

Although the new superconductor is isostructural to the previous "12442-type" ones, it shows contrasting structural and physical properties. First, the structural details in the FeAs layers are different from those of hole-doped 12442-type IBSCs, but similar to most electron-doped IBSCs. Second, the Hall-effect measurement shows negative Hall coefficient in the whole temperature range, and the Hall coefficient values are consistent with the electron doping level due to the oxygen substitution. Third, the superconducting properties such as the upper critical fields and specific-heat jump are close to most electron-doped IBSCs.

The onset resistive transition temperature of the new double-FeAs-layer IBSC is 30 K, and the zero-resistance temperature is 22 K. Correspondingly, the magnetic susceptibility and specific-heat data suggest two transitions, and the bulk superconductivity appears at 22 K. The result is in contrast with the single-FeAs-layer counterpart, ThFeAsN0.85O0.15, with the same doping level. The latter does not show superconductivity above1.8 K.

The essential role of inter-block charge transfer demonstrated seems to be insightful, which could be helpful for the exploration of broader layered materials beyond the layered IBSCs.
-end-
See the article: Ye-Ting Shao, Zhi-Cheng Wang, Bai-Zhuo Li, Si-Qi Wu, Ji-Feng Wu, Zhi Ren, Su-Wen Qiu, Can Rao, Cao Wang and Guang-Han Cao,"BaTh2Fe4As4(N0.7O0.3)2: an iron-based superconductor stabilized by inter-block-layer charge transfer," Sci. China Mater. (2019) doi: 10.1007/s40843-019-9438-7

This article was published online (http://engine.scichina.com/publisher/scp/journal/SCMs/doi/10.1007/s40843-019-9438-7?slug=fulltext)

Science China Press

Related Superconductor Articles from Brightsurf:

Researchers identify new type of superconductor
Until now, the history of superconducting materials has been a tale of two types: s-wave and d-wave.

Electric current is manipulated by light in an organic superconductor
A polarized petahertz current is driven by an ultrashort laser in an organic superconductor.

Editors' Choice in Science: an unusual superconductor
Professor Wang Jian at Peking University and collaborators observed the experimental evidence of anomalous metallic state and detected type-II Ising superconductivity existing in centrosymmetric systems.

New measurements reveal evidence of elusive particles in a newly-discovered superconductor
Now a team of researchers at the University of Illinois, led by physicist Vidya Madhavan, in collaboration with researchers from the National Institute of Standards and Technology, the University of Maryland, Boston College, and ETH Zurich, have used high-resolution microscopy tools to peer at the inner-workings of an unusual type of superconductor, uranium ditelluride (UTe2).

Scientists see energy gap modulations in a cuprate superconductor
Scientists studying high-Tc superconductors at the US Department of Energy's Brookhaven National Laboratory have definitive evidence for the existence of a state of matter known as a pair density wave -- first predicted by theorists some 50 years ago.

CaPtAs: A new noncentrosymmetric superconductor
A research group from Zhejiang University in China has found that the noncentrosymmetric compound CaPtAs is a superconductor, which shows evidence for unconventional properties.

Quantum fluctuations sustain the record superconductor
Calculations performed by an international team of researchers from Spain, Italy, France, Germany, and Japan show that the crystal structure of the record superconducting LaH10 compound is stabilized by atomic quantum fluctuations.

Electronic map reveals 'rules of the road' in superconductor
Using a clever technique that causes unruly crystals of iron selenide to snap into alignment, Rice University physicists have drawn a road map that reveals the quantum ''rules of the road'' that electrons must follow in the enigmatic superconductor.

Princeton scientists discover surprising quantum effect in an exotic superconductor
Superconductors are already in use in various capacities, but newer iron-based superconductors have potential for future use.

Thorium superconductivity: Scientists discover new high-temperature superconductor
A group of scientists led by Artem Oganov of Skoltech and the Moscow Institute of Physics and Technology, and Ivan Troyan of the Institute of Crystallography of RAS has succeeded in synthesizing thorium decahydride (ThH10), a new superconducting material with the very high critical temperature of 161 kelvins.

Read More: Superconductor News and Superconductor Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.