Bhardwaj Vishal, Pal Satyendra Prakash, Varga Lajos K, Tomar Monika, Gupta Vinay, Chatterjee Ratnamala
Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi, 110016, India.
Wigner research center for Physics Hungarian Academy of Sciences, P.O.B. 49, H-1525, Budapest, Hungary.
Sci Rep. 2018 Jul 2;8(1):9931. doi: 10.1038/s41598-018-28382-1.
Recently, a number of ternary half-Heusler compounds have been predicted independently by several research groups as candidates for 3D topological insulators. In this work, we report the observation of a two-dimensional (2D) weak antilocalization (WAL) effect, one of the hall-marks of topological surface states, and Shubnikov-de Hass (SdH) quantum oscillations in <110> oriented DyPdBi (DPB) thin films grown on MgO (100) substrates. The films prepared by pulsed laser deposition technique under the optimized conditions, showed a textured structure with (110) planes parallel to the (100) plane of MgO. The measured WAL effect follows the Hikami-Larkin-Nagaoka (HLN) model and the extracted values of phase coherence length (l) and α are 420 nm and ~-0.52 respectively. The power law variation of l (T) indicates the presence of the 2D surface states in DPB film. The Dirac nature of the surface states is further confirmed by Landau-level fan diagram analysis of SdH oscillations of the magneto-transport data. This analysis shows a finite Berry phase of 0.90π ± 0.16, reasonably close to the expected π value. Sheet Carrier density, n ~ 2.56 × 10 cm, calculated from the SdH oscillations (f ~ 106 T) and Hall measurements agree well with each other. These findings demonstrate that the half Heusler DPB thin films (~15-20 nm) can be used as a suitable material for investigating the novel intrinsic quantum transport properties of surface Dirac fermions.
最近，几个研究小组独立预测了一些三元半赫斯勒化合物作为三维拓扑绝缘体的候选材料。在这项工作中，我们报告了在生长于MgO(100)衬底上的<110>取向DyPdBi(DPB)薄膜中观察到二维(2D)弱反局域化(WAL)效应，这是拓扑表面态的标志性特征之一，以及舒布尼科夫-德哈斯(SdH)量子振荡。通过脉冲激光沉积技术在优化条件下制备的薄膜呈现出一种织构结构，其(110)面与MgO的(100)面平行。所测得的WAL效应符合日高-拉金-长冈(HLN)模型，提取的相位相干长度(l)和α值分别约为420 nm和约-0.52。l(T)的幂律变化表明DPB薄膜中存在二维表面态。通过对磁输运数据的SdH振荡进行朗道能级扇形图分析，进一步证实了表面态的狄拉克性质。该分析显示有限的贝里相位为0.90π±0.16，合理地接近预期的π值。由SdH振荡(f106 T)和霍尔测量计算得到的面载流子密度n2.56×10 cm，二者吻合良好。这些发现表明，半赫斯勒DPB薄膜(15 - 20 nm)可作为研究表面狄拉克费米子新型本征量子输运性质的合适材料。
