One-Dimensional van der Waals Material Tellurium: Raman Spectroscopy under Strain and Magneto-Transport

Abstract

Experimental demonstrations of one-dimensional (1D) van der Waals material tellurium (Te) have been presented by Raman spectroscopy under strain and magneto-transport. Raman spectroscopy measurements have been performed under strains along different principle axes. Pronounced strain response along the c-axis is observed due to the strong intrachain covalent bonds, while no strain response is obtained along the a-axis due to the weak interchain van der Waals interaction. Magneto-transport results further verify its anisotropic property, which results in dramatically distinct magneto-resistance behaviors in terms of three different magnetic field directions. Specifically, phase coherence length extracted from weak antilocalization effect, L ≈ T, claims its two-dimensional (2D) transport characteristics when an applied magnetic field is perpendicular to the thin film. In contrast, L ≈ T is obtained from universal conductance fluctuations once the magnetic field is along the c-axis of Te, which indicates its nature of 1D transport along the helical atomic chains. Our studies, which are obtained on high quality single crystal Te thin film, appear to serve as strong evidence of its 1D van der Waals structure from experimental perspectives. It is the aim of this paper to address this special concept that differs from the previous well-studied 1D nanowires or 2D van der Waals materials.

Growth and Strain Engineering of Trigonal Te for Topological Quantum Phases in Non-Symmorphic Chiral Crystals

“…We obtained indirect characterization of the strain state of this and three similar curved Te nanowires from the same growth using Raman spectroscopy (Figure 5a). As expected, both uniaxial strain and hydrostatic pressure have been shown previously to significantly shift the position of Raman active modes in Te [35,52]. Focusing on the most intense mode in the Raman spectrum of Te, the A1 breathing mode, we find that straight Te nanowires display strongly uniform peak positions and widths (Figure 5b), while curved nanowires on average have broader peaks and significant shifts up and down in frequency, relative to straight wires.…”

“…To estimate the significance of frequency shifts of approximately 0.5 cm -1 , we note that hydrostatic pressure of 4 GPa shifts the A1 mode of Te lower by about 10 cm -1 [52], while the same mode shifts lower with c-axis uniaxial strain of 1% by 1 cm -1 [35]. Thus, the shifts observed in our experiment might correspond to equivalent pressures of approximately 0.2 GPa or strains of 0.5%.…”

“…In topological materials, the non-trivial band topology gives rise to a non-trivial Berry phase, which shifts the phase of quantum oscillations. Quantum oscillations on unstrained bulk [61,62] and 2D Te [35] have been reported under a moderate magnetic field. From the Landau fan diagram established from the Shubnikov-de Haas quantum oscillation in MR, however, trivial Berry phase has been extracted [63], which does not support the existence of topological band.…”

Tellurium: Fast Electrical and Atomic Transport along the Weak Interaction Direction

“…Two-dimensional (2D) materials, such as graphene, MoS 2 , black phosphorus and hexagonal boron nitride, show great promise for many applications, including electronics, optoelectronics, energy conversion, and energy storage 1 . Recently, few-layer Te joins the family of 2D materials [2][3][4][5][6][7] . It exhibits air-stable transistor performance comparable or superior to other 2D materials 7 , making Te attractive for nanoelectronics.…”

“…Therefore, it has been assumed that the interaction along the chain is strong and covalent, while between the chains is weak. Some papers claim that the inter-chain interaction is van der Waals (vdW) type 5,8,[11][12][13][14][15][16][17] . In anisotropic materials, the transport along weak interaction direction is usually much slower than that along chemical bond directions.…”