Nav: Home

Uncovering the superconducting phosphine: P2H4 and P4H6

March 19, 2019

Searching high-Tc superconductor has become a hot topic in physics since superconducting mercury was first reported more than one century ago. Dense hydrogen was predicted to metalize and become superconductor at high pressure and room temperature. However, it has been very challenging and no widely accepted experimental work has been reported yet. In 2004, Ashcroft predicted hydrogen-dominant hydrides could become high-Tc superconductor at high pressure, due to the 'chemical precompression'. Later, Drozdov et al. observed the superconductive transition of H2S at 203 K and 155 GPa, which broke the highest Tc record. Very recently, LaH6 was reported to shown superconducting behavior at ~260K. Motivated by these works, extensive investigations on hydrides system have been reported.

PH3, a typical hydrogen-rich hydride, has attracted a great deal of research interest because of its superconducting transition discovered at high pressure. However, structural information was not provided, and the origin of the superconducting transition remains puzzling. Although a series of theoretical works suggested possible structures, the PH3 phase under compression has remained unknown and no relevant experimental studies have been reported.

In a recent research article published in National Science Review, scientists from the Center for High Pressure Science and Technology Advanced Research, School of Physics and Electronic Engineering, Jiangsu Normal University, Key Laboratory of Carbon Materials of Zhejiang Province, College of Chemistry and Materials Engineering, Wenzhou University and Shanghai Institute of Applied Physics, Chinese Academy of Sciences present their results on the studies of stoichiometric evolutions of PH3 under high pressure. It was found that PH3 is stable below 11.7 GPa and then it starts to dehydrogenate through two dimerization processes at room temperature and pressures up to 25 GPa. Two resulting phosphorus hydrides, P2H4 and P4H6, were verified experimentally and can be recovered to ambient pressure. Under further compression above 35 GPa, the P4H6 directly decomposed into elemental phosphorus. Low temperature can greatly hinder polymerization/decomposition under high pressure, and retain P4H6 up to at least 205 GPa. "Our findings suggested that P4H6 might be responsible for superconductivity at high pressures." said Dr. Lin Wang, the corresponding author of the article.

To determine the possible structure of P4H6 at high pressure, structural searches were further performed. Theoretical calculations revealed that two stable structures with space group Cmcm (< 182 GPa) and C2/m (> 182 GPa) were found. Phonon dispersions calculations of the two structures do not give any imaginary frequencies and therefore, this verifies their dynamic stabilities. The superconducting Tc of the C2/m structure at 200 GPa was estimated to be 67 K. "All of these findings confirmed P4H6 might be the corresponding superconductor, which is helpful for shedding light on the superconducting mechanism." Dr. Wang added.
-end-
This work was mainly supported by Natural Science Foundation of China (Grant No. 11874076), National Science Associated Funding (NSAF, Grant No. U1530402) and Science Challenging Program (Grant No. JCKY2016212A501).

See the article:

Ye Yuan, Yinwei Li, Guoyong Fang, Guangtao Liu, Cuiying Pei, Xin Li, Haiyan Zheng, Ke Yang, Lin Wang

Stoichiometric evolutions of PH3 under high pressure: implication for high Tc superconducting hydrides

Natl Sci Rev, https://doi.org/10.1093/nsr/nwz010

The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.

Science China Press

Related Physics Articles:

Diamonds coupled using quantum physics
Researchers at TU Wien have succeeded in coupling the specific defects in two such diamonds with one another.
The physics of wealth inequality
A Duke engineering professor has proposed an explanation for why the income disparity in America between the rich and poor continues to grow.
Physics can predict wealth inequality
The 2016 election year highlighted the growing problem of wealth inequality and finding ways to help the people who are falling behind.
Physics: Toward a practical nuclear pendulum
Researchers from Ludwig-Maximilians-Universitaet (LMU) Munich have, for the first time, measured the lifetime of an excited state in the nucleus of an unstable element.
Flowers use physics to attract pollinators
A new review indicates that flowers may be able to manipulate the laws of physics, by playing with light, using mechanical tricks, and harnessing electrostatic forces to attract pollinators.
Physics, photosynthesis and solar cells
A University of California, Riverside assistant professor has combined photosynthesis and physics to make a key discovery that could help make solar cells more efficient.
2-D physics
Physicist Andrea Young receives a 2016 Packard Fellowship to pursue his studies of van der Waals heterostructures.
Cats seem to grasp the laws of physics
Cats understand the principle of cause and effect as well as some elements of physics.
Plasma physics' giant leap
For the first time, scientists are looking at real data -- not computer models, but direct observation -- about what is happening in the fascinating region where the Earth's magnetic field breaks and then joins with the interplanetary magnetic field.
Nuclear physics' interdisciplinary progress
The theoretical view of the structure of the atom nucleus is not carved in stone.

Related Physics Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Changing The World
What does it take to change the world for the better? This hour, TED speakers explore ideas on activism—what motivates it, why it matters, and how each of us can make a difference. Guests include civil rights activist Ruby Sales, labor leader and civil rights activist Dolores Huerta, author Jeremy Heimans, "craftivist" Sarah Corbett, and designer and futurist Angela Oguntala.
Now Playing: Science for the People

#520 A Closer Look at Objectivism
This week we broach the topic of Objectivism. We'll be speaking with Keith Lockitch, senior fellow at the Ayn Rand Institute, about the philosophy of Objectivism as it's taught through Ayn Rand's writings. Then we'll speak with Denise Cummins, cognitive scientist, author and fellow at the Association for Psychological Science, about the impact of Objectivist ideology on society. Related links: This is what happens when you take Ayn Rand seriously Another Critic Who Doesn’t Care What Rand Thought or Why She Thought It, Only That She’s Wrong Quote is from "A Companion to Ayn Rand"