A 3D view into chaos: Researchers visualize temperature-driven turbulence in liquid metal for the first time

Phys.org   March 11, 2024 Researchers in Germany conducted an experiment inside a cylinder filled with the ternary alloy GaInSn focusing on the manifestation and dynamics of the large-scale circulation (LSC) in turbulent liquid metal convection. The large-scale flow structures were classified and characterized at Rayleigh numbers by means  enabling the full reconstruction of the three-dimensional flow structures in the entire convection cell. They identified the dominating modes of the turbulent convection. The analysis revealed that a single-roll structure of the LSC alternates in short succession with double-roll structures or a three-roll structure. This was accompanied by dramatic fluctuations of the […]

Materials research explores design rules and synthesis of quantum memory candidates

Phys.org   March 11, 2024 Stoichiometric Eu3+ compounds have recently shown promise for building dense, optically addressable quantum memory as the cations’ long nuclear spin coherence times and shielded 4f electron optical transitions provide reliable memory platforms but finding rare linewidth behavior within a wide range of potential chemical spaces remains difficult. Researchers at the University of Illinois, Urbana─Champaign, have found density functional theory (DFT) procedures that reliably reproduce known phase diagrams and correctly predict two experimentally realized quantum memory candidates. They synthesized the double perovskite halide Cs2NaEuF6 which is an air-stable compound with a calculated band gap of 5.0 eV […]

New research on tungsten unlocks potential for improving fusion materials

Phys.org   March 13, 2024 Understanding phonon scattering has remained challenging and requires detailed information on interactions between phonons and electrons. An international team of researchers (USA – SLAC National Accelerator Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Sweden, Italy) used an ultrafast electron diffuse scattering technique to resolve the nonequilibrium phonon dynamics in femtosecond–laser-excited tungsten in both time and momentum. They determined transient populations of phonon modes which show strong momentum dependence initiated by electron-phonon coupling. For phonons near Brillouin zone border, they observed a transient rise in their population on a timescale driven by the strong electron-phonon […]

Preventing magnet meltdowns before they can start

Science Daily  March 11, 2024 Unlike conventional magnets where a normal zone expands typically quickly, and the stored energy is dissipated across a large volume of the windings, a normal zone in a High-temperature superconductor (HTS) magnet propagates slowly and, thus, can heat up quickly to high temperatures destroying the conductor. At the same time, growing experimental evidence suggests that HTS conductors can operate in a stable dissipative flux flow regime for a substantial range of operational currents before entering an irreversible thermal runaway. Researchers at Lawrence Berkeley National Laboratory proposed a simple criterion for the thermal runaway in HTS […]

You don’t need glue to hold these materials together—just electricity

Phys.org   March 13, 2024 Researchers at the University of Maryland discovered that hard, electrical conductors (e.g., metals or graphite) could be adhered to soft, aqueous materials (e.g., hydrogels, fruit, or animal tissue) by a low DC electric field. They applied 5 V DC to graphite slabs spanning a tall cylindrical gel of acrylamide which resulted in a strong adhesion between the anode (+) and the gel in about 3 min. This adhesion lasted after the field was removed. They called it hard–soft electroadhesion or EA[HS]. Depending on the material, adhesion occurred at the anode (+), cathode (−), or both electrodes. […]

Better neutron mirrors can reveal the inner secrets of matter

Science Daily  February 29, 2024 The state-of-the-art multilayer polarizing neutron optics has limitations, particularly low specular reflectivity and polarization at higher scattering vectors/angles, and the requirement of high external magnetic fields to saturate the polarizer magnetization. An international team of researchers (Sweden, Iceland, Switzerland, Germany) showed that, by incorporating 11B4C into Fe/Si multilayers, amorphization and smooth interfaces could be achieved, yielding higher neutron reflectivity, less diffuse scattering, and higher polarization. Magnetic coercivity was eliminated, and magnetic saturation could be reached at low external fields. According to the researchers this approach offered prospects for substantial improvement in polarizing neutron optics with […]

New class of 2D material displays stable charge density wave at room temperature

Phys.org  March 1, 2024 Charge density waves are emergent quantum states that spontaneously reduce crystal symmetry, drive metal-insulator transitions, and precede superconductivity. In low-dimensions, distinct quantum states arise, however, thermal fluctuations and external disorder destroy long-range order. A team of researchers in the US (University of Michigan, Harvard University) has stabilized ordered 2D charge density waves through endotaxial synthesis of confined monolayers of 1T-TaS2. Specifically, an ordered incommensurate charge density wave (oIC-CDW) was realized in 2D with dramatically enhanced amplitude and resistivity. By enhancing CDW order, the hexatic nature of charge density waves became observable. Upon heating via in-situ TEM, […]

Research team develops a more durable coating against ice

Phys.org  February 27, 2024 An international team of researchers (Austria, Italy) deposited gradient polymers in one step via initiated chemical vapor deposition as an effective coating to mitigate ice accretion and reduce ice adhesion. The gradient structures easily overcame adhesion, stability, and durability issues of traditional fluorinated coatings. The coatings showed promising ice phobic performance by reducing ice adhesion, depressing the freezing point, delaying drop freezing, and inhibiting ice nucleation and frost propagation. They confirmed that lipophobicity correlated with surface energy discontinuities at the surface plane resulting from the random orientation of the fluorinated groups of PFDA. It could be […]

Electrons become fractions of themselves in graphene

Science Daily  February 21, 2024 The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2. Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. At zero magnetic field, an international team of researchers (USA – […]

Physicists detect elusive ‘Bragg glass’ phase with machine learning tool

Phys.org  February 9, 2024 Detecting the Bragg glass phase has been challenging despite its sharp theoretical definition in terms of diverging correlation lengths. A team of researchers in the US (Cornell University, Stanford University, National Accelerator Laboratory, Argonne National Laboratory provided bulk probe evidence supporting a Bragg glass phase in the systematically disordered charge-density-wave material of PdxErTe3. They established a diverging correlation length in samples with moderate intercalation over a wide temperature range. According to the researchers their work advances our understanding of the complex interplay between disorder and fluctuation and the use of their analysis technique to target fluctuations […]