Distinct variation of electronic states due to annealing in T′-type La1.8Eu0.2CuO4 and Nd2CuO4
Distinct variation of electronic states due to annealing in T′-type La1.8Eu0.2CuO4 and Nd2CuO4
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T′型 La1.8Eu0.2CuO4 和 Nd2CuO4 中退火导致电子态的明显变化
DOI：
10.1103/physrevb.104.214504
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发表时间：
2021
影响因子：
3.7
通讯作者：
Fujita Masaki
中科院分区：
文献类型：
--
作者：
Asano Shun;Ishii Kenji;Matsumura Daiju;Tsuji Takuya;Kudo Kota;Taniguchi Takanori;Saito Shin;Sunohara Toshiki;Kawamata Takayuki;Koike Yoji;Fujita Masaki
We performed Cu-edge x-ray absorption fine-structure measurements on-type(LECO) and(NCO) to investigate the variation in the electronic state associated with the emergence of superconductivity due to annealing. The x-ray absorption near-edge structure spectra of as-sintered (AS) LECO are quite similar to those of AS NCO, indicating that the ground state of AS LECO is a Mott insulator. We clarified a significant variation in the electronic state at the Cu sites in LECO due to annealing. The electron density after annealingwas evaluated for both superconducting LECO and nonsuperconducting NCO and was found to be 0.40 and 0.05 electron per Cu atom, respectively. In LECO but not in NCO, extended x-ray absorption fine-structure analysis revealed a reduction in the strength of the Cu-O bond in theplane due to annealing, which is consistent with the screening effect on phonons in the metallic state. Since the amounts of oxygen loss due to annealingfor LECO and NCO are comparable, these results suggest distinct electron-doping processes in the two compounds. The electron doping in NCO approximately follows the relation; this can be understood if electrons are doped through oxygen deficiency, but the anneal-induced metallic nature and largein LECO suggest that a variation of the electronic band structure causes the self-doping of carriers. The origin of the difference in doping processes due to annealing is discussed in relation to the size of the charge-transfer gap.
