Quantum transport properties of β-Bi4I4 near and well beyond the extreme quantum limit

Abstract

We have investigated the magneto-transport properties of β-Bi4I4 bulk crystal, which was recently theoretically proposed and experimentally demonstrated to be a topological insulator. At low temperature T and magnetic field B, a series of Shubnikov-De Haas(SdH) oscillations are observed on the magnetoresistivity (MR). The detailed analysis reveals a light cyclotron mass of 0.1 me, and the field angle dependence of MR reveals that the SdH oscillations originate from a convex Fermi surface. In the extreme quantum limit (EQL) region, there is a metal-insulator transition occurring soon after the EQL. We perform the scaling analysis, and all the isotherms fall onto a universal scaling with a fitted critical exponent  ≈ 6.5. The enormous value of critical exponent  implies this insulating quantum phase originated from strong electron-electron interactions in high fields. However, in the far end of EQL, both the longitudinal and Hall resistivity increase exponentially with B, and the temperature dependence of the MR reveals an energy gap induced by the high magnetic field, signifying a magnetic freeze-out effect. Our findings indicate that bulk β-Bi4I4 is an excellent candidate for a 3D topological system for exploring EQL physics and relevant exotic quantum phases.

Nanoparticle-directed bimodal crystallization of the quasi-1D van der Waals phase, Bi4I4

“…29 Beyond their suitability as model phases for bottom-up growth of complex and dimensionally-resolved q-1D vdW nanostructures, bismuth halide crystals are of particular interest due to recent studies that experimentally demonstrated both weak and higher-order topological insulating (HOTI) behavior in these crystals. 21,[30][31][32][33][34][35][36] In these studies, the topological nature of bismuth halide phases has been shown to strictly originate from the precise orientation and stacking of the q-1D [Bi 4 X 4 ] n subunits in the bulk crystal and its exposed facets. This, among the many emergent 1D/q-1D vdW crystals with size-, dimensionality-, and orientation-dependent properties, further warrants the need to understand the growth principles that underpin the controlled crystallization of well-dened 1D/q-1D vdW nanocrystals from bottom-up routes.…”

Recent progress on the planar Hall effect in quantum materials

“…The magnetic field leads to the accumulation of charges along the transverse direction of the current, where the Hall resistance provides the information on the charge carrier density and mobility. [16,17] An intrinsic mag-netic moment in the magnetic materials can give rise to a Hall signal deviating from linear behavior due to the interplay of the magnetic moment and external magnetic field, i.e., anomalous Hall effect. [18][19][20] Furthermore, the spin-orbit coupling (SOC) strength plays the crucial role in the (inverse) spin Hall effect, resulting in the accumulation of spin polarization in the transverse direction.…”