Enhanced Berry Curvature Dipole and Persistent Spin Texture in the Bi(110) Monolayer

Abstract

Nonvanishing Berry curvature dipole (BCD) and persistent spin texture (PST) are intriguing physical manifestations of electronic states in noncentrosymmetric 2D materials. The former induces a nonlinear Hall conductivity while the latter offers a coherent spin current. Based on density-functional-theory (DFT) calculations, we demonstrate the coexistence of both phenomena in a Bi(110) monolayer with a distorted phosphorene structure. Both effects are concurrently enhanced due to the strong spin−orbit coupling of Bi while the structural distortion creates internal in-plane ferroelectricity with inversion asymmetry. We further succeed in fabricating a Bi(110) monolayer in the desired phosphorene structure on the NbSe 2 substrate. Detailed atomic and electronic structures of the Bi(110)/NbSe 2 heterostructure are characterized by scanning tunneling microscopy/spectroscopy and angle-resolved-photoemission spectroscopy. These results are consistent with DFT calculations which indicate the large BCD and PST are retained. Our results suggest the Bi(110)/NbSe 2 heterostructure as a promising platform to exploit nonlinear Hall and coherent spin transport properties together.

Coupled Spin-Valley, Rashba Effect, and Hidden Spin Polarization in WSi2N4 Family

“…The spin polarization of Bloch states is either parallel or antiparallel to the z -direction leading to the case of PST. These spin textures are different from widely reported locally existing persistent spin textures and are preserved in the whole BZ. − Therefore, the control of Fermi level to a specific part of BZ where PST occurs is not required. These full-zone persistent spin textures (FZPST) can be explained using the symmetry arguments.…”

Realizing a Superconducting Square-Lattice Bismuth Monolayer

“…This system attracted huge interest as a candidate of 2D topological insulator (TI) to realize a quantum spin Hall edge state. − Few-layer Bi(111) films were grown on various substrates, ,− and their flat layer version, bismuthene, was also realized with a large band gap and a well-defined quantum spin Hall edge state. , A puckered structure of α-Bi was also observed widely, which has a black phosphorus (BP)-like (A17) structure with nonsymmorphic symmetry. ,− Note that this puckered structure is intrinsically composed of two paired atomic layers. While this structure is topologically trivial, inversion symmetry breaking can induce an in-plane polarization field to result in ferroelectricity and a substantial Berry curvature dipole. , Moreover, the strain could readily drive it into a topological insulator phase by tuning the buckling height. , The other structure, a monolayer of Bi(110) bulk-like (A7) structure (Figure a) has the nonsymmorphic and glide mirror symmetry and is known to induce 2D Dirac fermions. − Despite rich electronic and topological properties of (110) films, the single atomic layer of rectangular Bi is rarely realized due probably to its instability with unsaturated p z dangling bonds; , it was reported only as a wetting layer or a sandwiched layer in very thin Bi(110) films. − …”

“…While this structure is topologically trivial, inversion symmetry breaking can induce an in-plane polarization field to result in ferroelectricity and a substantial Berry curvature dipole. 33,34 Moreover, the strain could readily drive it into a topological insulator phase by tuning the buckling height. 35,36 The other structure, a monolayer of Bi(110) bulk-like (A7) structure (Figure 1a symmetry and is known to induce 2D Dirac fermions.…”

Ferroic Berry Curvature Dipole in a Topological Crystalline Insulator at Room Temperature

“…In particular, the Berry curvature dipole (BCD), which is the first-order moment of Berry curvature, has attracted a great deal of attention because of its production of nonlinear transport. A good example of such nonlinear transport is the nonlinear Hall effect (NLHE), the second-order Hall response, which appears in material systems with inversion symmetry breaking, such as T d phase transition metal dichalcogenides (TMDs), − strained TMD, Moiré systems, , and monolayer ferroelectric materials. , The BCD along an arbitrary in-plane α direction, D α , in a two-dimensional system is expressed as follows: D α = prefix∫ normald 2 bold-italick false( 2 π false) 2 .25em ∂ f 0 ∂ k α normalΩ ( k ) where k is a wave vector, k α is a wave vector along α, f 0 is the Fermi distribution function, and Ω( k ) is the Berry curvature. Under the time-reversal symmetric condition, D α is zero in centrosymmetric materials.…”

“…A good example of such nonlinear transport is the nonlinear Hall effect (NLHE), the second-order Hall response, which appears in material systems with inversion symmetry breaking, such as T d phase transition metal dichalcogenides (TMDs), 1−4 strained TMD, 5 Moirésystems, 6,7 and monolayer ferroelectric materials. 8,9 The BCD along an arbitrary in-plane α direction, D α , in a twodimensional system is expressed as follows:…”