Temperature dependent local atomic displacements in NaSn2As2 system
Temperature dependent local atomic displacements in NaSn2As2 system
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DOI：
10.1088/1361-648x/ab2bd4
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
G. Pugliese;F. Stramaglia;Y. Goto;K. Terashima;L. Simonelli;H. Fujiwara;A. Puri;C. Marini;M. Y. Hacisalihoglu;F. d’Acapito;T. Yokoya;T. Mizokawa;Y. Mizuguchi;N. Saini
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文献类型：
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作者：
G. Pugliese;F. Stramaglia;Y. Goto;K. Terashima;L. Simonelli;H. Fujiwara;A. Puri;C. Marini;M. Y. Hacisalihoglu;F. d’Acapito;T. Yokoya;T. Mizokawa;Y. Mizuguchi;N. Saini
NaSn2As2是一种机械剥离的层状van der Waals(VDW)Zint1相，由于其低的热导率和最近观察到的超导电性而引起人们的兴趣。在这里，我们用As K边和SnK边扩展的X射线吸收精细结构测量相结合的方法研究了NaSn2As2的局域温度相关结构。该系统本质上是无序的，原子间距离与平均结构测量所估计的基本一致。利用随温度变化的均方相对位移确定了不同键距的拉伸力常数。与以VDW型键为特征的较弱层间距不同，锡-砷间距是该体系中最强的键，具有共价性。其中，As-Na距离在∼200K以下略弱于锡-锡(I)，在此温度以上有增强的趋势。As-Na键的反常行为表明，该体系的机械剥离可能与温度有关。层间原子关联的异常可能是由于早期实验表明的在该温度附近的电荷密度波状不稳定性所致。讨论了NaSn2As2的局域结构和无序与其物理性质的关系。
NaSn2As2 is mechanically exfoliable layered van der Waals (vdW) Zintl phase that is getting interesting due to its low thermal conductivity and recently observed superconductivity. Here, we have investigated the temperature dependent local structure of NaSn2As2 by a combined analysis of As K-edge and Sn K-edge extended x-ray absorption fine structure measurements. The system is intrinsically disordered with the interatomic distances largely consistent to those estimated by average structure measurements. The stretching force constants of different bond distances have been determined using temperature dependent mean square relative displacements. The Sn–As distance is the strongest bond in this system, having covalent nature, unlike the weaker interlayer distances which are characterized by vdW type bonding. Among them, As–Na distance is slightly weaker than Sn–Sn(i) below ∼200 K and tends to get stronger above this temperature. The anomalous behavior of As–Na bond suggests that the mechanical exfoliation in this system is likely to be temperature dependent. The anomaly in the interlayer atomic correlations may be due to a charge density wave-like instability around this temperature, indicated by earlier experiments. The local structure and disorder are discussed in relation to the physical properties of NaSn2As2.