Dramatically decreased magnetoresistance in non-stoichiometric WTe2 crystals

Yang-Yang Lv,Yulin Chen,Y B Chen,Minghui Lu,Da-Jun Lin,Bin Pang,Yan-Feng Chen,Bin-Bin Zhang,Shu-Hua Yao,Xiao Li,Zhongkai Liu,Shan-Tao Zhang,Fan Zhang,Jian Zhou

doi:10.1038/srep26903

Abstract

Recently, the layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~105%), which can be useful for magnetic memory and spintronic devices. However, the underlying mechanisms of the giant magnetoresistance are still under hot debate. Herein, we grew the stoichiometric and non-stoichiometric WTe2 crystals to test the robustness of giant magnetoresistance. The stoichiometric WTe2 crystals have magnetoresistance as large as 3100% at 2 K and 9-Tesla magnetic field. However, only 71% and 13% magnetoresistance in the most non-stoichiometry (WTe1.80) and the highest Mo isovalent substitution samples (W0.7Mo0.3Te2) are observed, respectively. Analysis of the magnetic-field dependent magnetoresistance of non-stoichiometric WTe2 crystals substantiates that both the large electron-hole concentration asymmetry and decreased carrier mobility, induced by non-stoichiometry, synergistically lead to the decreased magnetoresistance. This work sheds more light on the origin of giant magnetoresistance observed in WTe2.

Highlights

The layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~105%), which can be useful for magnetic memory and spintronic devices
The main physical origin of giant MR is attributed to the nearly perfect compensation of electron and hole pockets[3]. This opinion is supported by subsequent Fermi surface determination by angle-resolved photoemission spectroscopy (ARPES)[6], as well as suppressed MR under external mechanical pressure[7]
It suggests that the exposed surface of crystals (see Fig. 1(a)) belongs to ab-plane and the thinnest dimension is along the c-axis

Summary

Introduction

The layered semimetal WTe2 has attracted renewed interest owing to the observation of a non-saturating and giant positive magnetoresistance (~105%), which can be useful for magnetic memory and spintronic devices. Giant (~1.5 × 105% at 2 K and 9 Tesla magnetic field) and non-saturated MR is observed in two-dimensional (2D) layered transition-metal dichalcogenides WTe23 It leads to a series of works to study the novel physical properties of WTe2, such as superconductivity with Tc as high as 7 K under external mechanical pressure[4], and possible quantum spin Hall effect in monolayer WTe2 with bulk electronic energy band-gap as large as 100.0 meV5. The origin of extremely large MR is an important physical problem, and valuable to device application of WTe2 As it was proposed, the main physical origin of giant MR is attributed to the nearly perfect compensation of electron and hole pockets[3]. From the viewpoint of real application, our result suggests that significant MR is strongly dependent on the stoichiometry of WTe2

Methods

Results

Conclusion