Two-Dimensional Transport-Induced Linear Magneto-Resistance in Topological Insulator Bi₂Se₃ Nanoribbons

Abstract

We report the study of a novel linear magneto-resistance (MR) under perpendicular magnetic fields in Bi 2 Se 3 nanoribbons. Through angular dependence magneto-transport experiments, we show that this linear MR is purely due to two-dimensional (2D) transport, in agreement with the recently discovered linear MR from 2D topological surface state in bulk Bi 2 Te 3 , and the linear MR of other gapless semiconductors and graphene. We further show that the linear MR of Bi 2 Se 3 nanoribbons persists to room temperature, underscoring the potential of exploiting topological insulator nanomaterials for room temperature magneto-electronic applications.KEYWORDS: Topological insulator, Bi 2 Se 3 , nanoribbon, linear magneto-resistance, twodimensional transport Topological insulators (TI's) are quantum materials with conducting gapless surface state on the surface or edge of insulating bulk, 1-4 holding great promises in the fundamental study of topological ordering in condensed matter systems and applications in spintronic devices for the spin polarized surface state. The spin polarization and suppressed back scattering render 2D topological surface state an attractive platform for high mobility charge and spin transport devices. Recently, Bi 2 Se 3 and related materials have been proposed 5 and confirmed 6-8 as threedimensional (3D) TI's with a single Dirac cone for the surface state. Among these materials, Bi 2 Se 3 , which is a pure compound rather than an alloy like Bi x Sb 1-x , 9 owns a larger bulk band gap (0.3 eV), and is thought to be promising for room temperature applications. Although the existence of topological surface state in Bi 2 Se 3 has been established by surface sensitive techniques such as the angle-resolved photoemission spectroscopy, 6,7 extracting the transport properties of 2D surface state in 3D TI's has been plagued by the more dominating conductivity from bulk carriers. [10][11][12][13][14][15][16][17][18] With extremely high surface-to-volume ratio and thus larger surface contribution in transport, nanostructures of TI's are useful to distinguish 2D surface transport from 3D bulk transport in the heated study of topological surface state. Indeed, Aharonov-Bohm (AB) oscillations were discovered in Bi 2 Se 3 nanoribbons in the parallel magnetic field induced MR, proving the existence of a coherent surface conducting channel. 10 In this study, we explore

Catalyst-Free Growth of Millimeter-Long Topological Insulator Bi2Se3 Nanoribbons and the Observation of the π-Berry Phase

“…27 In Au-catalyzed VLS-grown Bi 2 Se 3 nanoribbons, the fit of oscillatory magnetoresistance to LK theory yields a Berry phase of (1.62±0.02)π. 13 Below, we will show that even a very weak contribution from bulk transport can affect the determination of the Berry phase. Figure 3(a) presents the angle dependent oscillatory resistances for sample #2.…”

“…Up to now, SdH quantum oscillations observed in Au-catalyzed VLS-grown Bi 2 Se 3 nanoribbons were either attributed to the bulk carriers 20 or, displayed only a small number of oscillation periods complicating the determination of crucial surface state parameters, such as the Berry phase. 13 In this Letter, we report the catalyst-free synthesis of Bi 2 Se 3 nanoribbons using a physical vapor deposition (PVD) approach. Strong SdH quantum oscillations with up to 11 cycles can be identified in the magnetoresistance of the synthesized Bi 2 Se 3 nanoribbons in intermediate magnetic fields (≤ 9 Tesla).…”

“…21 In experiments, however, Berry phases less than have been reported in various families of TI 22 and larger than π in VLS-grown Bi 2 Se 3 nanoribbons. 13 To understand this phenomenon, theoretical scenarios such as Zeeman coupling with the high magnetic fields and the nontrivial parabolic band dispersion of the Dirac cone 21,26 have been proposed. On the other hand, transport properties measured with superconducting electrical contacts on an exfoliated Bi 2 Se 3 crystal show a π phase shift at certain gate voltages.…”

Granularity Controlled Nonsaturating Linear Magnetoresistance in Topological Insulator Bi2Te3 Films

“…14,15 In the last few years, the rapid expansion of the emerging field of topological insulators (TIs) has again stimulated intensive research on the MR in these topological materials with non-trivial zero-gap Dirac-like surface states. [16][17][18][19][20][21][22][23][24][25][26] After the initial discovery of a LMR together with the two-dimensional (2D) quantum oscillations of MR from the surface states, 16,17 many further experiments confirmed the existence of LMR in TI materials. [18][19][20][21][22][23][24][25][26] 18,22 Utilizing tilted magnetic field measurement, the linear MR of single crystalline TI in perpendicular field was attributed to the 2D gapless topological surface states and of quantum origin.…”

“…[18][19][20][21][22][23][24][25][26] 18,22 Utilizing tilted magnetic field measurement, the linear MR of single crystalline TI in perpendicular field was attributed to the 2D gapless topological surface states and of quantum origin. [17][18][19][20] On the other hand, other MR analysis suggested that charge inhomogeneity and conductivity fluctuation are also important, despite the sample being high quality film or individual single crystalline flake. 21,25,26 For instance, when the transport is tuned from bulk to topological surface conduction by applying back gate, the strong enhancement of linear MR is accompanied by a strongly nonlinear Hall effect, alluding to the relevance of charge inhomogeneity.…”