Phys.org April 16, 2024 Harnessing the asymmetric electronic population in the conduction band induced by an intense single-color circularly polarized laser pulse an international team of researchers (Japan, India, Germany) developed a universal method to generate ultrafast photocurrent in both inversion-symmetric and inversion-broken Weyl semimetals with degenerate Weyl nodes at the Fermi level. They found that the induced photocurrent could be tailored by manipulating helicity and ellipticity of the employed laser. Their approach generated photocurrent in realistic situations when the Weyl nodes were positioned at different energies and had finite tilt along a certain direction. According to the researchers their […]
Category Archives: Topological materials
New method flips the script on topological physics
Science Daily January 25, 2024 The concept of topological phases is rather abstract, and the characterization of the spectral topology of mechanical structures has intrinsically relied on the a priori knowledge of idealized theoretical models. An international team of researchers (USA – University of Pennsylvania, the Netherlands, France) introduced and validated an experimental method to detect the topologically protected zero modes of mechanical structures without resorting to any modeling step. The method is based on a simple electrostatic analogy: Topological zero modes are akin to electric charges. To detect them, they identified elementary mechanical molecules and measured their chiral polarization. […]
Scientists create novel approach to control energy waves in 4D
Science Daily July 31, 2023 Topological pumping allows waves to navigate a sample undisturbed by disorders and defects. An international team of researchers (USA – University of Missouri, China) demonstrated this phenomenon with elastic surface waves by strategically patterning an elastic surface to create a synthetic dimension. The surface was decorated with arrays of resonating pillars that were connected by spatially slow-varying coupling bridges and support eigenmodes located below the sound cone. They established a connection between the collective dynamics of the pillars and that of electrons in a magnetic field by developing a tight-binding model and a WKB (Wentzel-Kramers-Brillouin) […]
Topological materials become switchable
Phys.org October 10, 2022 An international team of researchers (Austria, the Netherlands, USA – Los Alamos National Laboratory, Rice University) used a special material made of cerium, bismuth, and palladium to demonstrate that it is possible to control topological properties and even make them disappear completely at a certain point to achieve stable, robust properties that can be selectively turn on and off. This control was made possible by the internal structure of the excitations, which are responsible for charge transport: They carry not only electric charge, but also a magnetic moment—and this makes it possible to switch them through […]
Future information technologies: Topological materials for ultrafast spintronics
Phys.org July 16, 2021 To understand how fast excited electrons in the bulk and on the surface of Sb react to the external energy input, and to explore the mechanisms governing their response an international team of researchers (Germany, Russia, Ireland) used time-, spin- and angle-resolved photoemission to femtosecond-laser excitation. The data showed a ‘kink’ structure in transiently occupied energy-momentum dispersion of surface states, which can be interpreted as an increase in effective electron mass. They were able to show that this mass enhancement plays a decisive role in determining the complex interplay in the dynamical behaviors of electrons from […]
Scientists observe complex tunable magnetism in a topological material
Science Daily March 23, 2021 An international team of researchers (USA – Ames Laboratory, Iowa State University, University of Missouri Research Reactor, Oak Ridge National Laboratory, Harvard University, Canada) discovered that EuIn2As2 has collinear antiferromagnetic order where the magnetic moment direction determines either a topological-crystalline-insulator phase supporting axion electrodynamics or a higher-order-topological-insulator phase with chiral hinge states. They used neutron diffraction, symmetry analysis, and density functional theory results to demonstrate that EuIn2As2 exhibits low-symmetry helical antiferromagnetic order which makes it a stoichiometric magnetic topological-crystalline axion insulator protected by the combination of a 180∘ rotation and time-reversal symmetries: C2×T=2′. Surfaces protected […]
Newly observed phenomenon could lead to new quantum devices
MIT News June 15, 2020 Kohn anomalies reflect a sudden change in the graph describing a change of the capability of electrons for shielding phonons. This can give rise to instabilities in the propagation of electrons through the material and can lead to many new electronic properties. A team of researchers in the US (MIT, Pennsylvania State University, Argonne National Laboratory, Oak Ridge National Laboratory, NIST, University of Maryland) predicted and observed Kohn anomaly in the topological Weyl semimetal (WSM) tantalum phosphide. It exhibits multiple topological singularities of Weyl nodes, leading to a distinct nesting condition with chiral selection, a […]