Diamond vise turns hydrogen into a metal potentially ending 80year quest

first_img Click to view the privacy policy. Required fields are indicated by an asterisk (*) Sang-Heon Shim, Arizona State University Scientists have already made liquid metal hydrogen—the substance thought to form the interior of giant planets like Jupiter—by ramping up pressure at higher temperatures. Silvera wanted to work at low temperatures and transform hydrogen into something still more exotic: solid metal. At cryogenic temperatures, hydrogen is a liquid. As the pressure rises, the liquid quickly becomes a nonmetallic solid (see diagram, left). In 1935, Princeton University physicists Eugene Wigner and Hillard Bell Huntington predicted that beyond 25 GPa, the nonconductive solid hydrogen would become metallic. But experimentalists passed that threshold decades ago with no sign of a solid metal.Silvera and Dias claim they’ve pushed their cell into an unexplored realm of low temperature and extreme pressure, succeeding in part because they avoided continuous high-intensity laser monitoring that they say can also cause an anvil’s diamonds to fail. Eventually, as they neared 500 GPa, the black sample became shiny and reddish. A low-intensity infrared laser—one that wouldn’t risk stressing the diamonds—revealed a strong spike in the sample’s reflectance, as expected from a metal. Only then did the Harvard pair use a different laser, in a procedure called Raman spectroscopy, to verify the peak pressure in the diamond cell.Silvera and Dias concede that their reddish silver speck could be a liquid rather than a solid, and they have not dared to release it from their diamond-tipped vise. But they are confident it is a metal—a “very convincing” claim, says Neil Ashcroft, a Cornell University physicist who predicted the superconductive state of hydrogen nearly 50 years ago.Eremets and others say they need more proof that the team has created a solid metal or even a metal at all. “We see only one experiment. It should be reproduced,” Eremets says. He also wonders whether the team actually reached the claimed 495 GPa, because that is usually determined through continuous Raman laser monitoring. Except for the final 495-GPa Raman measurement, Silvera and Dias were forced to estimate pressures from the number of turns of the screws on their anvils. Raymond Jeanloz, a high-pressure physicist at the University of California, Berkeley, also wants to be sure the trapped speck is pure hydrogen, because the gasket or the diamond coating could have broken down and reacted at high pressures. “It has fooled people in the past,” he says.But Silvera remains steadfast. A comparison of reflectance measurements from the center of the hydrogen dot and the surrounding gasket at 495 GPa suggests the hydrogen in the sample is pure, he says. As for the pressure measurement, Silvera insists he and Dias have studied it closely and verified their calibration.Silvera says they have just one experiment to report because they wanted to announce their result before running further tests that could break their vise. Soon, he says, they plan to run additional Raman laser tests that should reveal whether the sample has the regular atomic lattice expected of a solid metal. Eventually they will unscrew the vice and see whether the metal is metastable.Then, they will begin the experiment again. Claiming total victory in the “hydrogen wars,” as Jeanloz calls them, will require another round or two of evidence. Diamond vise turns hydrogen into a metal, potentially ending 80-year quest Country * Afghanistan Aland Islands Albania Algeria Andorra Angola Anguilla Antarctica Antigua and Barbuda Argentina Armenia Aruba Australia Austria Azerbaijan Bahamas Bahrain Bangladesh Barbados Belarus Belgium Belize Benin Bermuda Bhutan Bolivia, Plurinational State of Bonaire, Sint Eustatius and Saba Bosnia and Herzegovina Botswana Bouvet Island Brazil British Indian Ocean Territory Brunei Darussalam Bulgaria Burkina Faso Burundi Cambodia Cameroon Canada Cape Verde Cayman Islands Central African Republic Chad Chile China Christmas Island Cocos (Keeling) Islands Colombia Comoros Congo Congo, the Democratic Republic of the Cook Islands Costa Rica Cote d’Ivoire Croatia Cuba Curaçao Cyprus Czech Republic Denmark Djibouti Dominica Dominican Republic Ecuador Egypt El Salvador Equatorial Guinea Eritrea Estonia Ethiopia Falkland Islands (Malvinas) Faroe Islands Fiji Finland France French Guiana French Polynesia French Southern Territories Gabon Gambia Georgia Germany Ghana Gibraltar Greece Greenland Grenada Guadeloupe Guatemala Guernsey Guinea Guinea-Bissau Guyana Haiti Heard Island and McDonald Islands Holy See (Vatican City State) Honduras Hungary Iceland India Indonesia Iran, Islamic Republic of Iraq Ireland Isle of Man Israel Italy Jamaica Japan Jersey Jordan Kazakhstan Kenya Kiribati Korea, Democratic People’s Republic of Korea, Republic of Kuwait Kyrgyzstan Lao People’s Democratic Republic Latvia Lebanon Lesotho Liberia Libyan Arab Jamahiriya Liechtenstein Lithuania Luxembourg Macao Macedonia, the former Yugoslav Republic of Madagascar Malawi Malaysia Maldives Mali Malta Martinique Mauritania Mauritius Mayotte Mexico Moldova, Republic of Monaco Mongolia Montenegro Montserrat Morocco Mozambique Myanmar Namibia Nauru Nepal Netherlands New Caledonia New Zealand Nicaragua Niger Nigeria Niue Norfolk Island Norway Oman Pakistan Palestine Panama Papua New Guinea Paraguay Peru Philippines Pitcairn Poland Portugal Qatar Reunion Romania Russian Federation Rwanda Saint Barthélemy Saint Helena, Ascension and Tristan da Cunha Saint Kitts and Nevis Saint Lucia Saint Martin (French part) Saint Pierre and Miquelon Saint Vincent and the Grenadines Samoa San Marino Sao Tome and Principe Saudi Arabia Senegal Serbia Seychelles Sierra Leone Singapore Sint Maarten (Dutch part) Slovakia Slovenia Solomon Islands Somalia South Africa South Georgia and the South Sandwich Islands South Sudan Spain Sri Lanka Sudan Suriname Svalbard and Jan Mayen Swaziland Sweden Switzerland Syrian Arab Republic Taiwan Tajikistan Tanzania, United Republic of Thailand Timor-Leste Togo Tokelau Tonga Trinidad and Tobago Tunisia Turkey Turkmenistan Turks and Caicos Islands Tuvalu Uganda Ukraine United Arab Emirates United Kingdom United States Uruguay Uzbekistan Vanuatu Venezuela, Bolivarian Republic of Vietnam Virgin Islands, British Wallis and Futuna Western Sahara Yemen Zambia Zimbabwe A pressing matter Squeezing hydrogen at ultracold temperatures, scientists may have found the boundary where it becomes solid metal. (Hydrogen is a gas at low pressures, in a region too small to be seen in the lower left.) Last October, Harvard University physicist Isaac Silvera invited a few colleagues to stop by his lab to glimpse something that may not exist anywhere else in the universe. Word got around, and the next morning there was a line. Throughout the day, hundreds filed in to peer through a benchtop microscope at a reddish silver dot trapped between two diamond tips. Silvera finally closed shop at 6 p.m. to go home. “It took weeks for the excitement to die down,” Silvera says.That excitement swirled because by squeezing hydrogen to pressures well beyond those in the center of Earth, Silvera and his postdoc Ranga Dias had seen a hint that it had morphed into a solid metal, capable of conducting electricity. “If it’s true it would be fantastic,” says Reinhard Boehler, a physicist at the Carnegie Institution for Science in Washington, D.C. “This is something we as a community have been pushing to see for decades.”The feat, reported online this week in Science, is more than an oddity. Solid metallic hydrogen is thought to be a superconductor, able to conduct electricity without resistance. It may even be metastable, meaning that like diamond, also formed at high pressures, the metallic hydrogen would maintain its state—and even its superconductivity—once brought back to room temperatures and pressures. Still, claims of solid metallic hydrogen have come and gone before, and some experts want more proof. “From our point of view it’s not convincing,” says Mikhail Eremets, who is pursuing solid metallic hydrogen at the Max Planck Institute for Chemistry in Mainz, Germany. Others in the contentious field are downright hostile to the result. “The word garbage cannot really describe it,” says Eugene Gregoryanz, a high-pressure physicist at the University of Edinburgh, who objects to several of the experiment’s procedures.The dispute arises because high-pressure hydrogen experiments are hard to pull off, and even harder to interpret. First, scientists place a thin metal gasket between two flat-tipped diamonds. The gasket holds the hydrogen in place between the tips as the diamonds are cranked together. The intense pressure can force hydrogen into defects on the surface of the diamonds, causing them to become brittle and crack. So researchers have learned to apply transparent protective coatings to their diamonds. But the additional material makes it tricky to interpret laser measurements of what’s going on in the center. Furthermore, past pressures of about 400 gigapascals (GPa)—about 4 million times atmospheric pressure—the hydrogen turns black, preventing laser light from getting in. By Robert F. ServiceJan. 26, 2017 , 2:00 PM Using two diamonds, scientists squeezed hydrogen to pressures above those in Earth’s core. (Graphic) K. Sutliff/Science; (Data) Ranga Dias and Isaac Silvera, Harvard University Sign up for our daily newsletter Get more great content like this delivered right to you! Country Emaillast_img read more