Phys.org October 30, 2023 Rhombohedral-stacked multilayer graphene hosts a pair of flat bands touching at zero energy, which should give rise to correlated electron phenomena that can be tuned further by an electric field. An international team of researchers (USA – MIT, Harvard University, Japan) measured electron transport through hexagonal boron nitride-encapsulated pentalayer graphene down to 100 mK and observed a correlated insulating state with resistance at the megaohm level or greater at charge density n = 0 and displacement field D = 0. By increasing D, they observed a Chern insulator state with C = −5 and two other states with C = −3 at a magnetic field […]
Tag Archives: Topological materials
‘Topological gardening’ to achieve unexpected spin transport
Nanowerk August 22, 2023 In topological materials the interaction between the bulk state and edge states can be tuned to manipulate edge transport behavior, especially in topological crystalline insulators (TCI) which have multiple degrees of topological protection. This can open opportunities for novel electronic and spintronic applications. Researchers in Australia investigated how bulk-edge interactions can influence the edge transport in planar bismuthene, a TCI with metallic edge states protected by in-plane mirror symmetry. By exploring the impact of various perturbation effects, such as device size, substrate potentials, and applied transverse electric field, they examined the evolution of the electronic structure […]
How one photon becomes four charge carriers
Phys.org April 14, 2023 In a usual solar cell, the energy of a single photon is transferred to two free charges in the material. However, a few molecular materials like pentacene are an exception and show conversion of one photon into four charges, instead. This excitation doubling, which is called exciton fission, could be extremely useful for high-efficiency photovoltaics, specifically to upgrade the dominant silicon-based technologies. An international team of researchers (Germany, Canada) used time- and angle-resolved photoemission spectroscopy to observe the primary step of singlet fission in crystalline pentacene. Their results indicated a charge-transfer mediated mechanism with a hybridization […]
Exotic electronic effect found in 2D topological material
Phys.org September 26, 2022 When external or intrinsic parameters break symmetries, global properties of topological materials change drastically. While a rich variety of non-trivial quantum phases could in principle also originate from broken time-reversal symmetry, realizing systems that combine magnetism with complex topological properties is remarkably elusive. An international team of researchers (Germany, USA – UC Davis) demonstrated that giant open Fermi arcs are created at the surface of ultrathin hybrid magnets where the Fermi-surface topology is substantially modified by hybridization with a heavy-metal substrate. The interplay between magnetism and topology allows for control of shape and the location of […]
Triangular honeycombs: Physicists design novel quantum material
Nanowerk September 14, 2021 Using molecular beam techniques researchers in Germany succeeded in depositing a single layer of indium atoms as triangular lattice on a silicon carbide crystal as support resulting in indenene. The relevant electrons occupy free space in between the indium positions. Their charge fills the “negative” of the triangular indium lattice which is actually a honeycomb lattice. Unlike graphene, indenene needs not to be cooled down to ultra-low temperatures to manifest its properties as a topological insulator. The simple structure of indenene represents at the same time a challenge: as soon as the single layer of indium […]
A new direction of topological research is ready for take off
Phys.org June 1, 2021 An international team of researchers (Germany, Italy, USA – University of Maryland) has accomplished synthetic topological matter in electric circuit networks. The main motif of topological matter is its role in hosting particularly stable and robust features immune to local perturbations, which might be a pivotal ingredient for future quantum technologies. The current results promise a knowledge transfer from electric circuits to alternative optical platforms. Topolectric circuits create an experimental and theoretical inspiration for new avenues of topological matter and might have a particular bearing on future applications in photonics. The flexibility, cost-efficiency, and versatility of […]
Topological states caught in the act
Nanowerk October 23, 2020 Topological insulators do not conduct electricity in their bulk but channel it along their surface through edge modes. The edge modes can be destroyed only through the use of force. This topological property makes such materials promising candidates in future quantum devices when combined with Floquet engineering. An international team of researchers (USA – SLAC National Accelerator Laboratory, Stanford University, The Flatiron Institute, Spain, Germany, Switzerland) has demonstrated that short corkscrew laser flashes can be used to track these short-lived states. In their earlier work the researchers had demonstrated how to make use of circular dichroism […]