Nanowerk April 24, 2024 Extensive efforts have been undertaken to combine superconductivity and the quantum Hall effect so that Cooper-pair transport between superconducting electrodes in Josephson junctions is mediated by one-dimensional edge states. So far it has proven challenging to achieve detectable supercurrents through quantum Hall conductors. An international team of researchers (UK, South Korea, Spain, Japan, USA – Yale University) showed that domain walls in minimally twisted bilayer graphene support exceptionally robust proximity superconductivity in the quantum Hall regime, allowing Josephson junctions to operate in fields close to the upper critical field of superconducting electrodes. The critical current was […]
Category Archives: Superconductor
Scientists shed light on the inner workings of a new class of unconventional superconductors
Phys.org February 7, 2024 The discovery of superconductivity in infinite-layer nickelates established another category of unconventional superconductors that shares structural and electronic similarities with cuprates. However, key issues of the superconducting pairing symmetry, gap amplitude and superconducting fluctuations are yet to be addressed. A team of researchers in the US (Ames National Laboratory, SLAC National Laboratory, Stanford University) utilized static and ultrafast terahertz spectroscopy and demonstrated that the equilibrium terahertz conductivity and non-equilibrium terahertz responses of an optimally Sr-doped nickelate film are in line with the electrodynamics of d-wave superconductivity in the dirty limit. The gap-to-Tc ratio of 3.4 indicated […]
Controlling waves in magnets with superconductors for the first time
Science Daily October 26, 2023 For spintronics spin-waves have emerged as a promising platform that can offer new functionalities because of their wave nature. However, control of the spin-waves has remained a formidable challenge. Researchers in the Netherlands used superconducting diamagnetism to shape the magnetic environment governing the transport of spin waves in a thin-film magnet. Using diamond-based magnetic imaging, they observed hybridized spin-wave–Meissner-current transport modes with strongly altered, temperature-tunable wavelengths and then demonstrated local control of spin-wave refraction using a focused laser. According to the researchers their results demonstrate the versatility of superconductor-manipulated spin-wave transport and have potential applications […]
Physicists open new path to an exotic form of superconductivity
Phys.org August 8, 2023 Understanding the interplay of band topology and electronic interactions in topological systems remains a frontier question. A team of researchers in the US (Emory University, Stanford University) predicted new interacting electronic orders emerging near higher order Van Hove singularities present in the Chern bands of the Haldane model. They classified the nature of such singularities and employed unbiased renormalization group methods that unveiled a complex landscape of electronic orders, which included ferromagnetism, density waves, and superconductivity. Importantly, they showed that repulsive interactions could stabilize the long-sought pair-density-wave state and an exotic Chern supermetal, which is a […]
Scientists use lasers to recreate ‘twisted’ superconducting material
Phys.org March 21, 2023 In strong correlations and superconductivity in twisted-bilayer graphene the superposition of two twisted honeycomb lattices generating a moiré pattern is the key to the observed flat electronic bands, slow electron velocity and large density of states. An international team of researchers (USA – University of Chicago, China) demonstrated quantum simulation of superfluid to Mott insulator transition in twisted-bilayer square lattices based on atomic Bose–Einstein condensates loaded into spin-dependent optical lattices. The lattices are made of two sets of laser beams that independently address atoms in different spin states, which form the synthetic dimension accommodating the two […]
Researchers gain deeper understanding of mechanism behind superconductors
Phys.org January 17, 2023 High-temperature superconducting cuprates respond to doping with a dome-like dependence of their critical temperature (Tc). But the family-specific maximum Tc can be surpassed by application of pressure. Researchers in Germany investigated the phenomenon with high-pressure anvil cell NMR and measured the charge content at planar Cu and O, and with it the doping of the CuO2. They found that pressure increases the overall hole doping but when it enhances Tc above what can be achieved by doping, pressure leads to a hole redistribution favoring planar O. This is similar to the observation that the family-specific maximum […]
Leading the way in superconductor research: New compounds of lanthanum and hydrogen
Phys.org November 22, 2022 An international team of researchers (Germany, UK, Sweden, USA – University of Chicago) has presented the results of their single-crystal X-ray diffraction studies on lanthanum hydrides which revealed an unexpected chemical and structural diversity of lanthanum hydrides synthesized in the range of 50 to 180 GPa. They produced seven lanthanum hydrides LaH3, LaH~4, LaH4+δ, La4H23, LaH6+δ, LaH9+δ, and LaH10+δ, and determined the atomic coordinates of lanthanum in their structures. The regularities in rare-earth element hydrides the team has shown provide clues to guide the search for other synthesizable hydrides and candidate high-temperature superconductors. The hydrogen content variability […]
Physicists discover a “family” of robust, superconducting graphene structures
MIT News July 8, 2022 Despite multitudes of correlated phases observed in moiré systems, robust superconductivity appears the least common, found only in magic-angle twisted bilayer graphene (MATBG) and more recently in magic-angle twisted trilayer graphene. An international team of researchers (USA – MIT, Japan) has reported experimental realization of superconducting magic-angle twisted four-layer and five-layer graphene, hence establishing alternating twist magic-angle multilayer graphene as a robust family of moiré superconductors. This finding suggests that the flat bands shared by the members play a central role in the superconductivity. Their measurements in parallel magnetic fields reveal a clear distinction between […]
Characterizing the materials for next-generation quantum computers with nonlinear optical spectroscopy
Phys.org July 1, 2022 An international team of researchers (Germany, UC Irvine) developed a microscopic theory for the 2D spectroscopy of one-dimensional topological superconductors. They considered a ring geometry of an archetypal topological superconductor with periodic boundary conditions, bypassing energy-specific differences caused by topologically protected or trivial boundary modes that are hard to distinguish. They showed numerically and analytically that the cross-peak structure of the 2D spectra carries unique signatures of the topological phases of the chain. According to the researchers their work reveals how 2D spectroscopy can identify topological phases in bulk properties…read more. TECHNICAL ARTICLE
Developing next-generation superconducting cables
Science Daily May 24, 2022 Previous work showed that the body of superconducting cables could be cooled with helium gas, but the cable ends needed another medium for cooling, such as liquid nitrogen. To improve efficiency and practicality a team of researchers in the US (University of Colorado, Florida State University, industry) overcame that obstacle and were able to cool an entire cable system with helium gas. Removing the need for liquid nitrogen allowed them to make a highly compact superconducting power cable that can be operated in a continuous mode. The system is small and lightweight, and it allows […]