Strange quantum effect found in an exotic superconductor
Researchers discovered a mysterious quantum effect that breaks a 60-year-old physics theorem.
- Princeton scientists lead an international team that discovered unusual behavior in iron-based superconductors.
- The researchers observed how adding cobalt atoms disrupted superconductivity.
- The experiment demonstrated unexpected quantum behavior.
An international team of researchers observed an unexpected quantum effect in an exotic superconductor. Their discovery can lead to the next generation of energy-saving technologies.
Traditional superconductors, used for conducting electricity without resistance, work at low temperatures. However, some iron-based superconductors discovered about a decade ago, work at high temperatures. How they do it has been unclear, especially as the magnetism of iron conflicts with the appearance of superconductivity, explains the press release from Princeton, whose scientists led the research.
Figuring out how these iron-based superconductors operate could open doors to new applications, prompting the focus of researchers. They probed these materials by adding impurities — atoms of cobalt — to see how superconductivity was created and dissipated. Introducing cobalt has been shown to make iron-based superconductors to lose the property of superconductivity. It starts acting like a regular metal, where electrical flow is met with resistance and loss of energy.
The team's leader, M. Zahid Hasan, Professor of Physics at Princeton University, likened their approach to throwing a stone in the water to see how water would react, pointing out "The way the superconducting properties react to the impurity reveals their secrets with quantum-level detail."
Their team employed a technique called scanning tunneling microscopy to image individual atoms in a superconductor made of lithium, iron and arsenic while they added in cobalt atoms. They were able to observe how introducing more cobalt atoms made superconductivity disappear.
What was surprising, the researchers found that the cobalt atoms were able to disrupt electron pairing while replacing iron atoms in the metal. This behavior, which resulted in a quantum phase transition, changing the state from superconducting to non-superconducting, also violated the well-established Anderson's theorem. Proposed in 1959 by the Nobel Prize-winning physicist Philip Anderson, it was the accepted explanation for what would happen if you added impurities to a superconductor. The new research clearly shows an exception to Anderson's theorem.
Another unusual find revealed that the cobalt impurities also transformed the nature and the shape of the so-called "energy gap" - a feature emblematic of superconductivity. The shape of the gap is indicative of the "order parameter" linked to the nature of the superconductivity. The effect on this property is mysterious and points to a sign change in the order parameter's phase.
From left to right: Graduate student Nana Shumiya, Professor M. Zahid Hasan, Postdoctoral Research Associate Jia-Xin Yin and Graduate Student Yuxiao Jiang. Photo by Zijia Cheng
Credit: Princeton University
Postdoctoral researcher Ilya Belopolski, the co-author of the study, explained the significance of the researchers' feat:
"Naively, distinguishing between conventional superconductivity and sign-changing superconductivity requires a phase-sensitive measurement of the superconducting order parameter, which can be extremely challenging," said Belopolski. "A beautiful aspect of our experiment is that by considering violations of Anderson's theorem, we can get around this requirement.
Check out the study published in Physical Review Letters.
What would happen if you tripled the US population? Join Matthew Yglesias and Charles Duhigg at 1pm ET on Monday, September 28.
Whether or not women think beards are sexy has to do with "moral disgust"
- A new study found that women perceive men with facial hair to be more attractive as well as physically and socially dominant.
- Women tend to associate more masculine faces with physical strength, social assertiveness, and formidability.
- Women who display higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, are more likely to prefer hairy faces.
Beards and perceptions of masculinity<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg0MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY0NzkxMjM3N30.cH-GqNwP5GVqvstgJWAhBPn1B_lYpVEAI0I7iax7EQw/img.jpg?width=1245&coordinates=0%2C1900%2C0%2C849&height=700" id="caae6" class="rm-shortcode" data-rm-shortcode-id="cb0a355a4e8e1899789bc45f3f7aef56" data-rm-shortcode-name="rebelmouse-image" />
Photo Credit: Wikimedia<p>The study used 919 American (mostly white) women ages 18-70 who rated 30 pictures of men they were shown with various stages of facial hair growth. The photographs depicted men with faces that had been digitally altered to look more feminine or more masculine, with a beard and without a beard. The women rated the men according to perceived attractiveness for long-term and short-term relationships. The study found that the more facial hair the men had, the higher the men were rated on their attractiveness, particularly for their suitability for a long-term relationship.</p><p>Part of this might be attributed to facial masculinity — i.e. protruding brow ridge, wide cheekbones, thick jawline, and deeply set narrow eyes — which conveys information to a woman about a man's underlying health and formidability. Women tend to associate more masculine faces with physical strength and social assertiveness. It can also indicate a man with a superior immune response. The researchers suggested that their findings favoring bearded men could be due to the fact that facial hair enhances the masculine facial features on a man's face, like creating the illusion of a thicker jaw line. This could communicate direct benefits to women like resources and protection that would enhance survival among mothers and their infants. In other words, while a beard doesn't mean superior genetics in and of itself, it might be a primitive, ornamental way of saying, "Hey girl, I'm a testosterone-fueled lean, mean, pathogen fighting machine." <br></p><p>It could also be that a beard becomes its own destiny. The researchers in this study cite prior research that found that by growing a beard, men felt more masculine and had higher levels of serum testosterone, which was linked to a higher level of social dominance. They also tended to subscribe to more old-school beliefs about gender roles in their relationships with women as compared to men with clean-shaven faces.<span></span><br></p>
What does disgust have to do with beard preference?<p>Obviously, not all women dig beards. The researchers were particularly interested in what traits make a women prefer bearded men over clean-shaven faces. They looked into several factors including a woman's disgust levels on various concepts, her desire to become pregnant, and her exposure to facial hair in her personal life. </p><p>According to the study, women who were not into facial hair were turned-off by potential parasites or other critters they imagined could be in the hair or skin. Women ranking high on this "ectoparasite disgust" scale might have viewed beards as a sign of poor grooming habits. However, women who ranked higher in levels of "pathogen" did find the bearded men to be desirable, possibly because they perceived beards as a signal of good health and immune function. An intriguing discovery in the study was links to morality. Women who displayed higher levels of "moral disgust," or feelings of repugnance toward taboo behaviors, were more likely to prefer hairy faces. The authors opined that this could reflect a link between beardedness, politically conservative outlooks, and traditional views regarding performances of masculinity in heterosexual relationships.</p>
Additional findings<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjU5OTg1My9vcmlnaW4uZ2lmIiwiZXhwaXJlc19hdCI6MTYyNDI1NjUyOX0.P9B8WbmJR0q4nfzYZKbuNSA-2SAigVWJgrQE-_Gxlds/img.gif?width=980" id="49143" class="rm-shortcode" data-rm-shortcode-id="2ed3b1d6f20fc170bf2974646e565e8d" data-rm-shortcode-name="rebelmouse-image" />Giphy<p>The correlations that existed between married and single women's rating on the attractiveness of beards were not particularly clear, although the researchers noted that single and married women who wanted children tended to find beards more attractive than the women who didn't want children. They also found that women with bearded husbands found beards to be more attractive, which might indicate that social exposure to beards influences how desirable they are perceived of as being. Or it could be that men with wives who like beards grow beards.</p><p>It's important to note that culture plays a huge role in how attractive women perceive certain male characteristics as being. This study looked at a small, culturally specific group of American women, so no big, universal claims should be made about masculinity, facial hair, and male desirability to women. However, research like this is important in highlighting how human grooming decisions are driven by much more than fashion trends. Sociobiological, economic, and ecological factors all play a part in the way we choose to present ourselves.</p>
Dominique Crenn, the only female chef in America with three Michelin stars, joins Big Think Live.
Having been exposed to mavericks in the French culinary world at a young age, three-star Michelin chef Dominique Crenn made it her mission to cook in a way that is not only delicious and elegant, but also expressive, memorable, and true to her experience.
New experiments find weird quantum activity in supercold gas.
Quantum Mechanics, Onions, and a Theory of Everything<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="036ae7b8dd661df2d125a3421a0299ba"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/bcVruA0AJ-o?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Researchers say that moral self-licensing occurs "because good deeds make people feel secure in their moral self-regard."
Books about race and anti-racism have dominated bestseller lists in the past few months, bringing to prominence authors including Ibram Kendi, Ijeoma Oluo, Reni Eddo-Lodge, and Robin DiAngelo.