International Conference on Condensed Matter Physics
Calculations motivated by the successful prediction of the nickelate phase diagram suggest that palladates might hit the sweet spot for high-temperature superconductivity.
Copper-based (cuprate) superconductors have long held the record for the highest superconducting critical temperature (Tc) at ambient pressure. In 2019, after decades of theoretical and experimental effort, researchers reported a nickel-based (nickelate) analog to cuprate superconductors (see Trend: Entering the Nickel Age of Superconductivity). Since then, others have sought to pinpoint the factors that control superconductivity in such single-orbital-dominated systems. Motoharu Kitatani of the University of Hyogo in Japan and his colleagues now identify some of these factors and suggest that swapping out nickel for palladium could deliver a material that superconducts at even higher temperatures than cuprate superconductors [1]. The study could help guide the ongoing search for novel superconducting materials and establish “palladates” as the new kid on the block.
Kitatani and his colleagues previously had used a standard condensed-matter-physics model, called the single-band Hubbard model, to predict Tc for nickelates and had validated their predictions using measurements in defect-free nickelate films. Now, by simulating this system while varying the electrons’ interaction strength, filling factor, and energy-momentum dispersion, the researchers have tracked the strength of electron–electron pairing that leads to the emergence of superconductivity. This allows them to determine the electronic configuration that optimizes Tc. However, according to their results, neither nickelates nor cuprates come close to these optimized conditions. Instead, the researchers have found that palladates, thanks to somewhat weaker interactions and thus weaker correlations, could more closely approach the optimal “Goldilocks” conditions that maximize Tc. The researchers hope their theoretical results will encourage experimentalists to grow and examine palladates as new candidates for higher-Tc options.
International Conference on Condensed Matter Physics Researchers from the Institute of Theoretical Physics (ITP) of the Chinese Academy of Sciences (CA S) and Shanghai Jiao Tong University (SJTU) have found that granular matter (such as sand) and some black hole models display similar nonlinear effects. The bridge between the two is the holographic duality. Holographic duality allows one to map unsolved physical problems to tractable higher-dimensional gravitational counterparts and vice versa. The mapping between different dimensions resembles the optical holographic projection technique, hence the name. Although the holographic duality originated from string theory and was part of the quest for a consistent theory of quantum gravity, it has also been widely applied to quantum chromodynamics, condensed matter physics, and quantum information. In this work, the idea of holographic duality is extended to a concrete type of athermal, disordered solids—granular materials. Sinc...
International Conference on Condensed Matter Physics In 1934, Eugene Wigner, a pioneer of quantum mechanics, theorized a strange kind of matter — a crystal made from electrons. The idea was simple; proving it wasn’t. Physicists tried many tricks over eight decades to nudge electrons into forming these so-called Wigner crystals, with limited success. In June, however, two independent groups of physicists reported in Nature the most direct experimental observations of Wigner crystals yet. “Wigner crystallization is such an old idea,” said Brian Skinner, a physicist at Ohio State University who was not involved with the work. “To see it so cleanly was really nice.” To make electrons form a Wigner crystal, it might seem that a physicist would simply have to cool them down. Electrons repel one another, and so cooling would decrease their energy and freeze them into a lattice just as water turns to ice. Yet cold electrons obey the odd laws of quantum mechanics — they behave like waves....
Exploiting ultra-confined and highly directional polaritons at the nanoscale is essential for developing integrated nanophotonic devices, circuits and chips. High-symmetry crystals have been extensively studied, with a particular focus on hyperbolic polaritons (HPs). However, the in-plane HP propagation in high-symmetry optical crystals usually exhibits four mirror-symmetric beams, which reduces the directionality and energy-transporting efficiency. In a new paper published in eLight, a team of scientists led by Professor Xinliang Zhang and Peining Li from Huazhong University of Science and Technology and Professor Zhigao Dai from China University of Geosciences have developed a new technique for in-plane anisotropic excitation and propagation of HPs by controlling the near-field excitation source. Their research could expand the possibilities for manipulating asymmetric polaritons, where it could be applied to reconfigurable polaritonic devices. Recently, hyperbolic shear polaritons,...
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