Millimetre-long transport of photogenerated carriers in topological insulators
Millimetre-long transport of photogenerated carriers in topological insulators
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DOI：
10.1038/s41467-019-13711-3
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发表时间：
2019-12
影响因子：
16.6
通讯作者：
Yasen Hou;Rui Wang;Ruijuan Xiao;L. McClintock;Henry Clark Travaglini;John Paulus Francia;H. Fetsch;O. Erten;S. Savrasov;Baigeng Wang;A. Rossi;I. Vishik;E. Rotenberg;Dong Yu
中科院分区：
文献类型：
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作者：
Yasen Hou;Rui Wang;Ruijuan Xiao;L. McClintock;Henry Clark Travaglini;John Paulus Francia;H. Fetsch;O. Erten;S. Savrasov;Baigeng Wang;A. Rossi;I. Vishik;E. Rotenberg;Dong Yu
激子是自旋的整数粒子，预计会在足够低的温度下凝聚成相干量子态。在这里，我们报道了利用光电流成像的实验证据，证明了Bi2-xSbxSe3纳米带中非平衡激子的形成和有效输运。光电流分布与电场无关，说明光激发电子和空穴形成激子。值得注意的是，这些激子在40 K复合之前可以沿着拓扑绝缘体(TI)纳米带传输几百微米。宏观传输距离结合由瞬时光电流测量获得的短载流子寿命，表明激子扩散系数至少为36 m~2s−1，相当于在7 K时的迁移率为6 × 104m2V−1s−1，比TIS中报道的自由载流子的迁移率高4个数量级。高无耗散激子输运的观测表明，TIS表面形成了类超流态激子凝聚体。
Excitons are spin integer particles that are predicted to condense into a coherent quantum state at sufficiently low temperature. Here by using photocurrent imaging we report experimental evidence of formation and efficient transport of non-equilibrium excitons in Bi2-xSbxSe3nanoribbons. The photocurrent distributions are independent of electric field, indicating that photoexcited electrons and holes form excitons. Remarkably, these excitons can transport over hundreds of micrometers along the topological insulator (TI) nanoribbons before recombination at up to 40 K. The macroscopic transport distance, combined with short carrier lifetime obtained from transient photocurrent measurements, indicates an exciton diffusion coefficient at least 36 m2s−1, which corresponds to a mobility of 6 × 104m2V−1s−1at 7 K and is four order of magnitude higher than the value reported for free carriers in TIs. The observation of highly dissipationless exciton transport implies the formation of superfluid-like exciton condensate at the surface of TIs.