New superconductors are both ordinary yet odd


superconductor

Crystal structure of Guloy's unconventional superconductor © ACS

Two new superconducting materials have been created: one’s unconventional, while the other is more conventional except for one difference, it doesn’t contain any transition metals. While the materials’ origins and characteristics are quite different both have layered structures, suggesting a new avenue for superconductivity research.

Arnold Guloy’s team at the University of Houston, Texas, US, has created a new example of what are known as ‘unconventional superconductors’ using titanium. Unconventional superconductors, also called high temperature superconductors, were first developed by creating layered cuprate pnictides. Iron arsenide pnictide-based high temperature superconductors followed and now layered titanium pnictides have also been shown to exhibit this unconventional superconductivity.1

Unconventional superconductors are so-called because the materials are normally insulating and it’s doping that allows the material to become superconducting. ‘They have very complicated phase diagrams,’ explains Guloy, ‘the key feature is that there are competing ordered states.’ So to find other materials that demonstrated these properties, Guloy’s team went looking for structures analogous to the current pnictide based superconductors, with their layered structures doped with metal atoms that act as charge reservoirs between the layers.

The new material, Ba1–xNaxTi2Sb2O, however, is superconducting at quite low temperatures (around 5.5K) compared with the cuprates. Nevertheless, Guloy says it took experimentation to raise the temperature of the cuprate superconductors. His lab is now working to play around with the material to try and improve it.

superconductor

Awana's superconductor also has a layered structure (Bi, violet; S, yellow; O, green) © ACS

Guloy is also sure that the new material will help with further investigation of these unconventional superconductors, which are still not well understood.

Meanwhile, in India, different layered structures which mimic cuprate superconductors have created a superconductor in the absence of a transition metal.2

Veer Awana’s group have shown that Bi4O4S3 does exhibit bulk superconductivity, with the superconductivity originating from the BiS2 layers because, according to Awana, of the strong hybridisation or correlations between the bismuth and sulfur sp orbitals. ‘The novel thing about [Awana’s work] is that, again, it’s based on layered structures,’ adds Guloy. ‘That’s the cool thing about it, there’s a new superconducting layer based on BiS, which is surprising.’

Both scientists say the opportunities opened up by these new materials could lead superconductivity research in new directions with Guloy saying that the possibility of combining these two pieces of work would be ‘challenging and quite exciting’.


Related Content

YBCO - Yttrium Barium Copper Oxide

8 May 2013 Podcast | Compounds

news image

Neil Withers recalls making this groundbreaking superconductor as a student

Good vibrations brighten superconductor outlook

13 November 2014 Research

news image

By coupling to phonons in their selenium titanate substrate’s lattice, electrons in iron selenide become superconductive be...

Most Read

UC Davis chemist sentenced to four years over explosion

19 November 2014 News and Analysis

news image

Postdoc sentenced over attempt to make explosive device and reckless disposal of hazardous waste

Spanish fly

10 October 2013 Podcast | Compounds

news image

Helen Scales looks at cantharidin, the active ingredient in this famous aphrodisiac

Most Commented

Beetle behind breath test for bank notes

17 November 2014 Research

news image

Photonic crystal inks inspired by longhorn beetle could help to fight counterfeiting

Bayer wins race to buy Merck & Co consumer care

9 May 2014 Business

news image

$14bn deal will make Aspirin inventor the number two over-the-counter healthcare company