Topological current divider in a Chern insulator junction

Abstract

A Chern insulator is a two-dimensional material that hosts chiral edge states produced by the combination of topology with time reversal symmetry breaking. Such edge states are perfect one-dimensional conductors, which may exist not only on sample edges, but on any boundary between two materials with distinct topological invariants (or Chern numbers). Engineering of such interfaces is highly desirable due to emerging opportunities of using topological edge states for energy-efficient information transmission. Here, we report a chiral edge-current divider based on Chern insulator junctions formed within the layered topological magnet MnBi2Te4. We find that in a device containing a boundary between regions of different thickness, topological domains with different Chern numbers can coexist. At the domain boundary, a Chern insulator junction forms, where we identify a chiral edge mode along the junction interface. We use this to construct topological circuits in which the chiral edge current can be split, rerouted, or switched off by controlling the Chern numbers of the individual domains. Our results demonstrate MnBi2Te4 as an emerging platform for topological circuits design.

High-order harmonics from elliptically polarized laser for classification of topological states in 2D Chern insulators and 2D topological insulators

“…Such quantum materials with non-trivial topology are interesting candidates for the study of fundamental physical phenomena and advanced technologies [7][8][9][10][11]. For example, a CI has conducting edge states with gapped bulk states; they can be used in energy-efficient electronic devices [12]. In a TI, non-trivial topological states are protected by time-reversal symmetry (TRS).…”

Tunable Magnetic Domains in Ferrimagnetic MnSb2Te4

“…So far, the use of magnetism to control electronic properties in magnetic topological materials has been explored primarily in terms of topological phase transitions (e.g., refs 10, 12, 31, and 32) and manipulating chiral edge modes of the quantum anomalous Hall effect. 11,33,34 Edge mode manipulation has been demonstrated via magnetic domains in Cr-doped (Bi,Sb) 2 Te 3 33,34 and via layer-dependent magnetization in antiferromagnetic MBT. 11 In magnetic materials more generally, domain manipulation and control has long been demonstrated using a variety of techniques including electrical currents, magnetic field gradients, and local magnetic fields, e. prospects for manipulating the local magnetization to create configurable devices.…”

“…11,33,34 Edge mode manipulation has been demonstrated via magnetic domains in Cr-doped (Bi,Sb) 2 Te 3 33,34 and via layer-dependent magnetization in antiferromagnetic MBT. 11 In magnetic materials more generally, domain manipulation and control has long been demonstrated using a variety of techniques including electrical currents, magnetic field gradients, and local magnetic fields, e. prospects for manipulating the local magnetization to create configurable devices. Specifically, we use the domain imaging and writing capabilities of magnetic force microscopy (MFM) combined with in situ transport to directly measure the device response to local changes in magnetization.…”

“…The recent discovery of MnBi 2 Te 4 (MBT) − was a breakthrough to realize the quantum anomalous Hall effect in a stoichiometric crystal, avoiding the need for disorder-inducing magnetic dopants. − In addition, crystals are exfoliatable down to few layer thicknesses enabling integration into Van der Waals heterostructures with well developed fabrication techniques. ,− This discovery was rapidly followed by work extending MBT into a family of materials with highly tunable properties via crystallographic and chemical paradigms. ,,− Substituting Sb for Bi changes the doping from n-type to p-type. , However, surprisingly, within MST, the magnetic order can also be tuned (via the concentration of magnetic defects) from A-type antiferromagnetic seen in MBT, where planes of Mn moments are aligned ferromagnetically (antiferromagnetically) within the plane (between planes), to ferrimagnetic with net out of plane magnetization. ,,− The ability to tune the effective interplane coupling from antiferromagnetic to ferromagnetic strongly suggests the presence of magnetic frustration in M­(B,S)­T, raising the possibility of stabilizing other interesting magnetic orders. , …”

Universal Conductance Fluctuations in a MnBi2Te4 Thin Film

“…Below the Néel temperature ∼20 K, within each van der Waals layer magnetic moments on the Mn sites order ferromagnetically with an out-of-plane easy axis. Depending on external magnetic field and film thickness a variety of interlayer orderings have been observed, some associated with quantized Hall resistance or axion insulating states. − The well-defined stoichiometry implied by the chemical formula suggests that this should be a cleaner system than the more widely studied quaternary alloy Cr x (Bi,Sb) 2– x Te 3 . − However, in practice disorder is ubiquitous in both thin-film and bulk single-crystal samples of MBT. Sources of defects include antisite defects, − impurity phases, − and magnetic domains. , These have hindered experimental validation of striking predictions for behavior near B = 0 such as quantization of Hall resistance and persistence of topological phenomena at elevated temperatures …”