Phys.org September 19, 2024 Bulk van der Waals (vdW) superlattices hosting 2D interfaces between minimally disordered layers represent scalable bulk analogues of artificial vdW heterostructures and present a complementary venue to explore incommensurately modulated 2D states. An international team of researchers in the (USA- MIT, National High Magnetic Field Laboratory, Harvard, Japan) reported the bulk vdW superlattice SrTa2S5 realizing an incommensurate one-dimensional (1D) structural modulation of 2D transition metal dichalcogenide (TMD) H-TaS2 layers. High-quality electronic transport in the H-TaS2 layers was made anisotropic by the modulation and exhibited commensurability oscillations paralleling lithographically modulated 2D systems. They found unconventional, clean-limit superconductivity […]
Tag Archives: Superconductivity
Ultrasound experiment identifies new superconductor
Phys.org May 9, 2024 Uranium ditelluride (UTe2) has previously been inferred to have a multi-component order parameter, in part due to the apparent presence of a two-step superconducting transition in some samples. However, recent experimental observations in newer-generation samples have raised questions about this interpretation, pointing to the need for a direct probe of the order parameter symmetry. An international team of researchers (USA – Cornell University, University of Maryland, University of Wisconsin-Milwaukee, NIST, France, Canada) measured the elastic moduli of UTe2 in samples that exhibited both one and two superconducting transitions. They demonstrated the absence of thermodynamic discontinuities in […]
Researchers discover new yttrium-hydrogen compounds with implications for high-pressure superconductivity
Phys.org March 14, 2024 An international team of researchers (Germany, UK, USA – University of Chicago) used synchrotron single-crystal x-ray diffraction (SCXRD) and found (two YH3 phases) and five previously unknown yttrium hydrides. These were synthesized in diamond anvil cells by laser heating yttrium with hydrogen-rich precursors—ammonia borane or paraffin oil. The arrangements of yttrium atoms in the crystal structures of new phases were determined based on SCXRD, and the hydrogen content estimations based on empirical relations and ab initio calculations revealed the following compounds: Y3H11, Y2H9, Y4H23, Y13H75, and Y4H25. They also uncovered a carbide and two yttrium allotropes. […]
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 […]
Field-induced superconductivity in quantum materials
Phys.org December 12, 2023 Field-induced superconductivity is a rare phenomenon where an applied magnetic field enhances or induces superconductivity. A team of researchers in the US (MIT, Argonne National Laboratory, University of Washington, George Mason University) combined tunable uniaxial stress and applied magnetic field on the ferromagnetic superconductor Eu(Fe0.88Co0.12)2As2 to shift the field-induced zero-resistance temperature between 4 K and a record-high value of 10 K. They used x-ray diffraction and spectroscopy measurements under stress and field to reveal that strain tuning of the nematic order and field tuning of the ferromagnetism act as independent control parameters of the superconductivity. Combining […]
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 […]
Researchers achieve interdimensional superconductivity
Nanowerk July 19, 2023 Spatial disorder has been shown to drive two-dimensional (2D) superconductors to an insulating phase through a superconductor–insulator transition (SIT). Numerical calculations predict that with increasing disorder, emergent electronic granularity is expected in these materials—a phenomenon where superconducting (SC) domains on the scale of the material’s coherence length are embedded in an insulating matrix and coherently coupled by Josephson tunneling. An international team of researchers (USA – SLAC National Accelerator Laboratory, Colombia) has shown spatially resolved scanning tunneling spectroscopy (STS) measurements of the three-dimensional (3D) superconductor BaPb1−xBixO3 (BPBO), which surprisingly demonstrated three key signatures of emergent electronic […]
Reaching superconductivity layer by layer
Phys.org March 2, 2023 Multilayered graphene has many promising qualities ranging from widely tunable band structure and special optical properties to new forms of superconductivity. An international team of researchers (Austria, Israel) studied multilayer graphene for the possibility of creating topological superconductivity. In their theoretical model, simulated on a computer, they looked at various possible arrangements of different graphene sheets on top of each other and the behavior of electrons that move in the multiplayer graphene. Depending on how the different layers of graphene are shifted with respect to each other and on how many layers there were, the positively […]
Study: Superconductivity switches on and off in ‘magic-angle’ graphene
Pays.org January 30, 2023 Superconducting FETs operate through continuous tuning of carrier density, but no bistable superconducting FET, which could serve as a new type of cryogenic memory element, has been reported. Recently, gate hysteresis and resultant bistability in Bernal-stacked bilayer graphene aligned to its insulating hexagonal boron nitride gate dielectrics were discovered. An international team of researchers (USA- MIT, Israel) reported the observation of hysteresis in magic-angle twisted bilayer graphene (MATBG) with aligned boron nitride layers. The bistable behaviour coexists alongside the strongly correlated electron system of MATBG without disrupting its correlated insulator or superconducting states. The all-van der […]
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 […]