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 […]
Tag Archives: Materials science
A proof of odd-parity superconductivity
Phys.org July 12, 2022 Odd-parity superconductivity is rare in nature; only a few materials support this state, and in none of them has the expected angle dependence been observed. CeRh2As2 was recently found to exhibit two superconducting states: A low-field state changes into a high-field state at 4 T when a magnetic field is applied along one axis. Through a comprehensive study of the angle dependence of the upper critical fields using magnetic ac susceptibility, specific heat, and torque on single crystals of CeRh2As2 an international team of researchers (Germany, New Zealand, France, USA – University of Wisconsin) has shown […]
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
A four-stroke engine for atoms
Phys.org July 6, 2022 Electric control of magnetism and magnetic control of ferroelectricity can improve the energy efficiency of magnetic memory and data-processing devices. However, the necessary magnetoelectric switching is hard to achieve, and requires more than just a coupling between the spin and the charge degrees of freedom. An international team of researchers (Italy, Austria, USA – Rutgers University, the Netherlands) showed that an application and subsequent removal of a magnetic field reverses the electric polarization of the multiferroic GdMn2O5, thus required two cycles to bring the system back to the original configuration. During this unusual hysteresis loop, four […]
Physicists work to shrink microchips with first one-dimensional helium model system
Phys.org July 6, 2022 As the spatial dimension is lowered, locally stabilizing interactions are reduced, leading to the emergence of strongly fluctuating phases of matter without classical analogues. A team of researchers in the US (University of Tennessee, Argonne National Laboratory, Caltech, University of Indiana) describes the experimental observation of a one-dimensional quantum liquid of 4He using nanoengineering by confining it within a porous material preplated with a noble gas to enhance dimensional reduction. The resulting excitations of the confined 4He are qualitatively different than bulk superfluid helium and can be analyzed in terms of a mobile impurity allowing for […]
Cocrystal engineering—a clever way for designing multifunctional material
EurekAlert June 24, 2022 Using cocrystal engineering researchers in China have designed Flu-TCNQ cocrystal with integrated optoelectronic properties. They selected the Flu (donor) as the luminescence unit due to its good luminescence, extended π-conjugated plans, and rich electrons properties, and the TCNQ (acceptor) as the electrical building block, a typical n-type semiconductor that can provide a strong electron-withdrawing capacity. Driven by the charge transfer (CT) interaction and affected by the D-A molecules stacking mode, the emission of Flu-TCNQ cocrystal was regulated to be red, and the n-type charge transport property of the acceptor molecule was maintained in the cocrystal. According […]
Novel gel proves itself to be a highly tunable color filter
Phys.org June 27, 2022 A team of researchers in the US (NIST, University of Delaware) has developed a gel, they call “SeedGel’ which has the capability as a temperature-sensitive light filter. When white light is shone at the gel, depending on the gel’s temperature, only a specific wavelength will pass through it. A temperature change of less than a tenth of a degree Celsius can be enough to alter the permitted wavelength, which can be any color in the visible range as well as parts of the ultraviolet and infrared. The gel is made of water and liquid solvents with […]
Valleytronics researchers fabricate novel 2D material enjoying long-life excitons
Phys.org June 28, 2022 Researchers in China presented the observation of the IXs in trilayer type-II staggered band alignment of MoS2/MoSe2/WSe2 van der Waals (vdW) HSs by photoluminescence (PL) spectroscopy. The central energy of IX is 1.33 eV, and the energy difference between the extracted double peaks is 23 meV. They confirmed the origin of IX through PL properties and calculations by the density functional theory and studied the dependence of the IX emission peak on laser power and temperature. The polarization-resolved PL spectra of HS were also investigated, and the maximum polarizability of the emission peak of WSe2 reached […]
Physicists shine light on solid way to extend excitons’ life
Phys.org June 20, 2022 A team of researchers in the US (UT Austin, Auburn University) performed an extensive study of transient optical absorption of both W- and Mo-based single-crystalline monolayer TMDs grown by a recently developed laser-assisted evaporation method. All spectral features of the monolayers as grown on fused silica substrates exhibited appreciable redshifts relating to the existence of strain due to growth conditions. These systems exhibited a dramatic slowing down of exciton dynamics with an increase in carrier densities, which strongly contrasted with the monolayers in their freestanding form as well as in comparison with more traditionally grown TMDs. […]
New member added to carbon material family, a two-dimensional monolayer polymeric fullerene
Phys.org June 15, 2022 It is a challenge to prepare large-sized single-crystal 2D carbon materials with moderate bandgaps to complement zero-bandgap graphene. Researchers in Chia prepared a single-crystal 2D carbon material, namely monolayer quasi-hexagonal-phase fullerene (C60) via an interlayer bonding cleavage strategy. In this monolayer polymeric C60, cluster cages of C60 are covalently bonded with each other in a plane, forming a regular topology that is distinct from that in conventional 2D materials. It exhibited high crystallinity and good thermodynamic stability, and the electronic band structure measurement revealed a transport bandgap of about 1.6 electronvolts. An asymmetric lattice structure endows monolayer […]