The Superconductor Sensation Has Fizzled, and That’s Fine

2023-08-16 01:11:51
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It’s rare that condensed matter physics is the talk of the town. But recently a remarkable amount of Internet discussion and news coverage has revolved around a purported advance in the field: bombshell claims from a team of South Korean scientists professing to have discovered an ambient-pressure, room-temperature superconductor. Independent confirmation of the researchers’ claims would’ve meant that their buzzy new material—a compound of copper, lead, phosphorus and oxygen dubbed “LK-99”—could conduct electricity frictionlessly, without any loss of current, in a wider array of environmental conditions than any other known substance. Such a capability could, in principle, lead to revolutionary advances in power plants, energy grids, computers and transportation.

Yet weeks removed from the release of the initial research findings, those claims seem all but debunked. After a fortnight of unfettered positivity and interest on social media (including some amateur experimental attempts that were streamed on Twitch), authoritative efforts from physicists around the world to double-check the South Korean team’s claims have mostly deflated the hype. All of LK-99’s bizarre behavior that hinted at superconductivity—such as its partial levitation over a magnet—can apparently be explained away by odd but distinctly nonsuperconductive properties, such as ferromagnetism, the same structural quirk that allows magnetic fields to permeate iron and reconfigure the metal’s electrons.

Considering the new work, “[LK-99’s] room-temperature superconductivity seems less and less likely,” says Nadya Mason, a materials physicist at the University of Illinois at Urbana-Champaign. “The experimental papers showing ferromagnetism were pretty convincing, and the new theories are also more carefully done.” Richard Greene, a physicist studying superconductors at the University of Maryland, generally agrees. “It is still a bit too early to put the nail in the coffin,” he says. “But we are getting close. The coffin is there, the nails are ready, and a hammer is ready, too.”

Of course, the boom-and-bust cycle of LK-99 is a classic demonstration of science in action. The scientific method worked as it should. But in the fading afterglow of LK-99’s social-media-fueled rise and fall, it’s probably worth examining one dimension of what might’ve driven all that excitement in the first place. Many Internet posters, along with some researchers and journalists, have positioned a room-temperature superconductor as a technological panacea for climate change that could accelerate the world’s transition away from reliance on fossil fuels.

On the heels of Earth’s hottest month in recorded history, it’s easy to understand why people are eager for positive news and signs of progress. After all, with the perfect material, electricity could flow along transmission lines with flawless efficiency—but that’s just the start of potentially revolutionary applications. In principle, a room-temperature superconductor could lead to more compact wind turbines that are easier to build and less resource-intensive, says Susie Speller, a materials scientist specializing in superconductors at the University of Oxford. Electronic devices from computers to electric vehicles would need far less power if they all contained some ideal superconducting substance. Deeper into the land of hypotheticals, the right superconductor could enable scalable nuclear fusion reactors to offer an abundant source of carbon-free energy, Speller says.

Even if LK-99 had proved to be a room-temperature superconductor, its feasibility for addressing energy and climate concerns would rest on an exceedingly flimsy foundation of faraway “ifs.” If LK-99 were a superconductor, if it could withstand high currents, if it weren’t too brittle to form into wire, if it were easy and cheap to synthesize, if the materials for its manufacture could be readily acquired, and if policy and funding followed suit, then maybe it could provide a small boost for energy efficiency a decade or more down the line. In short, it would be far from the quick climate fix that the U.S. seems particularly hungry for.

Superconductivity alone isn’t enough. For a material to be useful in power generation and electronics, it would need to have many other exceptional qualities. Some superconductors lose their capacity to freely transport electricity at high currents or in the presence of magnetic fields, yet both abilities are necessary for an electrical component to be practical. Ductility and flexibility are also crucial, points out Michael Norman, director of the Quantum Institute at Argonne National Laboratory: if you can’t easily stretch LK-99 into a wire, then using it in turbines, transmission lines or fusion reactors becomes much more challenging. Processing a material into thin films could offer a wireless workaround, Norman notes, but then the problem becomes one of difficulty and cost—which has disqualified past proved superconducting products, such as cuprate tape, from being widely manufactured.

Beyond those questions of material properties, even the most ideal “all-weather” superconductor still wouldn’t solve climate change, Mason adds. That’s partially because it would bring only marginal improvements to the transmission lines of most state-of-the-art power grids, which are already quite efficient. “They only lose about 5 percent of their energy as heat,” Mason notes, and we’re not going to “solve climate change at the 5 percent scale.”

Pablo Duenas Martinez, an engineer studying energy decarbonization at the Massachusetts Institute of Technology, agrees. In his field, Duenas Martinez says, no one is really talking about superconductors. “We are more worried about, for example, materials for batteries,” he explains. For power grids, transmission losses are trivial compared to the harder problem of having sufficient energy storage to fully benefit from solar and wind power, which can only intermittently provide electricity. And beyond the need for better batteries, there are even harder problems still, such as the societal challenge of changing attitudes and behaviors that have held the world in thrall to fossil fuels for so long.

Boosting transmission efficiency, Duenas Martinez notes, doesn’t require wondrous superconductors at all and can instead be achieved with existing technology by simply updating old infrastructure. It’s a lack of investment, not a lack of possibility, that’s kept the grid as-is. Then, he adds, there are policy decisions, such as continuing to provide subsidies for fossil fuels, that maintain oil, gas and coal as artificially inexpensive options despite the fact that wind and solar power have rapidly become comparatively cheaper. Climate change is a problem that requires immediate and sustained action—on multiple fronts—if we’re to avoid ever worsening consequences. Our governments and global economies are so enmeshed with fossil fuels that the emissions crisis can’t be fixed by scientific or technological advances alone.

All that doesn’t mean the possibility of a practical room-temperature superconductor is worthless—such a thing would be an enormous boon for technological development and scientific research, perhaps in ways we can’t yet fully comprehend. But in retrospect, the enthusiasm surrounding LK-99 may well say more about our collective desire for easy answers and propensity for wishful thinking than it ever did about the potential of the material itself.

“We cannot wait for a disruptive technology to happen to start decarbonizing,” Duenas Martinez says. The wind turbines we have now aren’t perfect, but we need more of them. Power grids must be expanded and upgraded, even if doing so relies on transmission lines made from ordinary copper. Weaning ourselves from fossil fuels requires somehow moderating our enormous energy demands and rethinking economic myths of infinite growth. There is no silver (or LK-99) bullet that can snap the planet’s perilously warming climate back to some preindustrial idyll, Duenas Martinez emphasizes. At first, a floating rock might look like magic, but it isn’t—it never is.

参考译文
高温超导体热潮已经消退,这也没什么不好
在凝聚态物理成为热门话题的场合并不多见。但最近,围绕该领域的一项所谓重大进展,网上讨论和媒体报道数量惊人:一个韩国科学家团队声称发现了常压常温下的超导体。如果其他研究人员能确认这些说法,那么他们新发现的引人注目的材料——一种铜、铅、磷和氧的化合物,被命名为“LK-99”——便可以在比其他任何已知物质更广泛的环境条件下无摩擦地传导电流,而不会造成电流损失。从理论上讲,这种能力可以带来发电厂、能源网络、计算机和交通领域的革命性进步。然而,距离最初研究成果的公布仅数周,这些说法似乎已被几乎完全推翻。在社交媒体上经历了一两周的狂热和兴趣(包括一些在Twitch上直播的业余实验尝试)之后,世界各地的物理学家对韩国团队的说法进行了权威性的验证,大多让这种狂热逐渐消退。LK-99所表现出来的所有奇异行为——例如部分悬浮在磁铁之上——都可以被一些奇怪但完全非超导的特性所解释,比如铁磁性,这种结构特性使磁场能够渗透铁并重塑金属的电子结构。伊利诺伊大学厄巴纳-香槟分校的材料物理学家纳迪亚·梅森(Nadya Mason)表示,考虑到新近的研究工作,“LK-99的常温超导性似乎越来越不可能了”。“那些显示铁磁性的实验论文相当有说服力,而且新的理论也更加严谨。”马里兰大学研究超导体的物理学家理查德·格林(Richard Greene)基本同意这一点。“现在还为时过早去彻底否定它,”他说。“但我们已经非常接近了。棺材在那里,钉子已经准备好了,锤子也已经准备好。”当然,LK-99的涨跌周期是科学运作的一个经典示例。科学方法正如它应该的那样运作着。但在LK-99在社交媒体上兴衰的余波逐渐消退之际,也许值得探讨一下最初引发所有这些兴奋的可能因素之一。许多网友、研究人员和记者都将常温超导体视为应对气候变化的技术灵丹妙药,可以加速世界摆脱对化石燃料的依赖。在经历了有记录以来最热的一个月之后,人们渴望看到积极的新闻和进步的迹象,这一点很容易理解。毕竟能够用完美的材料沿着输电线路无损传导电力——但这只是潜在革命性应用的开始。牛津大学专门研究超导体的材料科学家苏西·斯帕勒(Susie Speller)表示,原则上,常温超导体可以带来更紧凑的风力涡轮机,更容易建造且资源消耗更少。如果所有电子设备,从计算机到电动汽车,都包含某些理想的超导材料,那么它们将需要更少的电能。更进一步,Speller指出,如果拥有合适的超导体,还能使可扩展的核聚变反应堆成为可能,从而为世界提供大量零碳排放的能源。即使LK-99被证明是常温超导体,它在应对能源和气候问题的可行性上,也将建立在极为脆弱的“如果”基础之上。如果LK-99是超导体,如果它能够承受高电流,如果它不会过于脆弱而无法制成导线,如果它易于且便宜地合成,如果其制造材料易于获取,同时如果政策和资金支持到位,那么也许十年后,它才能为能源效率带来一些微小的提升。简而言之,它距离美国渴望得到的快速气候解决方案还差得很远。超导性本身并不足够。为了在发电和电子领域发挥作用,材料还需要具备许多其他优异的性能。一些超导体在高电流或磁场环境中会失去自由传输电能的能力,而这两点能力对电气元件的实际应用却是必不可少的。阿贡国家实验室量子研究所所长迈克尔·诺曼(Michael Norman)指出,延展性和灵活性也是关键因素:如果你无法轻易地将LK-99拉伸成导线,那么将其用于涡轮机、输电线或聚变反应堆会变得更具挑战性。诺曼指出,将材料制成薄膜或许可以提供一种无线替代方案,但这样一来问题就变成了制造难度和成本问题——这正是过去一些经证实的超导产品(如铜氧化物磁带)未能广泛制造的原因。梅森补充道,即使是最理想的“全气候”超导体,也无法真正解决气候变化问题。部分原因是它对大多数先进电网中已经相当高效的输电线带来的改进只是边际性的。“它们只损失了大约5%的能量作为热能,”梅森指出,“我们无法在5%的层面‘解决’气候变化问题。”麻省理工学院研究能源脱碳的工程师帕布罗·杜纳斯·马丁内斯(Pablo Duenas Martinez)也表示同意。在杜纳斯·马丁内斯所在的领域,没人真正在谈论超导体。“我们更担心的是例如电池材料,”他解释道。对于电力网络来说,输电损耗在面临更棘手的问题——比如拥有足够的储能以充分利用太阳能和风能——相比之下根本微不足道,因为太阳能和风能只能间歇性地提供电力。而且在需要更好的电池之外,还有更艰难的问题,比如社会挑战,如改变长期使世界依赖化石燃料的态度和行为。杜纳斯·马丁内斯指出,提高输电效率根本不需要神奇的超导体,仅通过使用现有技术更新旧基础设施即可实现。电网保持现状的原因是缺乏投资,而非缺乏可能性。然后,他补充说,还有政策上的决定,例如继续为化石燃料提供补贴,这使得石油、天然气和煤炭成为人为廉价的选择,尽管风能和太阳能的成本已经迅速下降。气候变化是一个需要在多个领域立即并持续采取行动的问题,如果我们想要避免日益恶化的后果。我们的政府和全球经济与化石燃料联系如此紧密,以至于碳排放危机无法仅通过科学或技术进步来解决。这一切并不意味着实用的常温超导体的可能性毫无价值——这样的发现将对技术发展和科学研究带来巨大好处,可能在我们尚未完全理解的方面。但回顾来看,围绕LK-99的狂热很可能会比它本身的实际潜力更说明我们的集体渴望寻找捷径和容易的答案。杜纳斯·马丁内斯说道:“我们不能等着某项颠覆性技术出现才开始去实现去碳化。”我们现有的风力涡轮机并不完美,但我们需要更多。电力网络必须扩展和升级,即使这意味着使用普通铜制造的输电线路。摆脱化石燃料,需要我们以某种方式调节巨大的能源需求,并重新思考经济神话中关于无限增长的观念。杜纳斯·马丁内斯强调,没有银弹(或LK-99)能够让地球急剧变暖的气候瞬间回归到某个前工业化时代的伊甸园。起初,一块漂浮的石头可能看起来像魔法,但它不是——从来都不是。
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