Bandwidth-controlled Mott transition in κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x: Optical studies of correlated carriers
Bandwidth-controlled Mott transition in κ-(BEDT-TTF)2Cu[N(CN)2]BrxCl1-x: Optical studies of correlated carriers
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DOI：
10.1103/physrevb.79.195106
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发表时间：
2009-05-01
影响因子：
3.7
通讯作者：
Batail, Patrick
中科院分区：
文献类型：
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作者：
Dumm, Michael;Faltermeier, Daniel;Batail, Patrick
在二维有机电荷转移盐 kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]BrxCl1-x 中，Br 含量从 x=0 到 0.9 的系统变化使我们能够通过增加带宽来调整莫特跃迁。在低于 50 K 的温度下，富含 Cl 的样品中会形成能隙，并在 T -> 0 时增长至大约 1000 cm(-1)。随着 Br 浓度的增加，光谱权重移至能隙区域并最终将其完全填满。当 x=0.73、0.85 和 0.9 的样品在低温下变成金属时，由于相干准粒子，会出现德鲁德型响应。此处，准粒子散射率显示出 omega(2) 依赖性，并且载流子的有效质量得到增强，这与费米液体的预测一致。对于接近临界值 x(c) 约 0.7 的组合物，这些强电子-电子相互作用的典型特征更加明显，其中发生金属到绝缘体的转变。
In the two-dimensional organic charge-transfer salts kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]BrxCl1-x a systematic variation in the Br content from x=0 to 0.9 allows us to tune the Mott transition by increasing the bandwidth. At temperatures below 50 K, an energy gap develops in the Cl-rich samples and grows to approximately 1000 cm(-1) for T -> 0. With increasing Br concentration spectral weight shifts into the gap region and eventually fills it up completely. As the samples with x=0.73, 0.85, and 0.9 become metallic at low temperatures, a Drude-type response develops due to the coherent quasiparticles. Here, the quasiparticle scattering rate shows a omega(2) dependence and the effective mass of the carriers is enhanced in agreement with the predictions for a Fermi liquid. These typical signatures of strong electron-electron interactions are more pronounced for compositions close to the critical value x(c)approximate to 0.7, where the metal-to-insulator transition occurs.