Bayesian Spectroscopy on Polarization Dependent Photoluminescence Spectra of Doubly-Split Excitons in a Cu2O Thin-Crystal Sandwiched by MgO Substrates
Bayesian Spectroscopy on Polarization Dependent Photoluminescence Spectra of Doubly-Split Excitons in a Cu2O Thin-Crystal Sandwiched by MgO Substrates
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贝叶斯光谱法研究夹有 MgO 基板的 Cu2O 薄晶中双分裂激子的偏振相关光致发光光谱
DOI：
10.1002/pssb.201800136
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Akai Ichiro
中科院分区：
文献类型：
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作者：
Kiridoshi Arisa;Aihara Shingo;Arishima Syunshiro;Yamashiro Tetsuya;Mizumaki Masaichiro;Iwamitsu Kazunori;Akai Ichiro
利用贝叶斯光谱法研究了在MgO衬底间小间隙中重结晶的Cu2O薄晶体中双分裂1S黄色邻位激子的光致发光（PL）光谱的偏振依赖性。在这些薄晶体中，由于Cu2O和MgO之间的小晶格失配，预计会涉及双轴应力。在平面各向同性的双轴应力下，Cu2O中的立方对称性退化为四氢呋喃酮，随后，邻位激子态分裂为具有不同对称性的两个态。因此，预期双分裂邻位激子的共振PL强度显示出不同的偏振依赖性。为了阐明这种双轴应力效应，我们测量了4.2K下的PL谱的偏振依赖性。虽然双分裂激子态的共振弱PL带和它们的强声子边带共存，但我们成功地通过具有副本交换蒙特卡罗算法的贝叶斯光谱分解到各自的光谱分量。结果发现，出现在较高能量侧的共振PL带几乎不显示偏振依赖性，而出现在较低能量侧的共振PL带更弱并且显示显著的偏振依赖性。这些结果可以通过双分裂邻位激子态四极跃迁的跃迁矩阵元的选择定则和极化依赖性来解释，并且清楚地表明，Cu2O薄晶体中的各向同性双轴应力使晶体对称性退化到D4h。
By using Bayesian spectroscopy, we studied polarization dependence of photoluminescence (PL) spectra in doubly‐split 1S yellow ortho‐excitons in a Cu2O thin‐crystal recrystallized in a small gap between paired MgO substrates. In these thin‐crystals, biaxial stresses are expected to be involved due to a small lattice mismatch between Cu2O and MgO. Under a planar‐isotropic biaxial stress, the cubic symmetry degrades to the tetragonal one in Cu2O, and subsequently, the ortho‐exciton state splits into two states having different symmetries. Consequently, the resonant PL intensities of the doubly‐split ortho‐excitons are expected to show different polarization dependencies. To elucidate such biaxial stress effect, we measured polarization dependence of the PL spectra at 4.2 K. Although resonant weak PL bands of the doubly‐split exciton states and their intense phonon sidebands co‐exist, we succeeded in decomposing to the respective spectral components by the Bayesian spectroscopy with a replica exchange Monte Carlo algorithm. As a result, it is found that the resonant PL band appearing on higher energy side shows hardly polarization dependence, whereas the resonant PL band appearing on lower energy side is further weak and shows noticeable polarization dependence. These results can be explained by the selection rule and polarization dependences on the transition matrix elements of quadrupole transitions of the doubly‐split ortho‐exciton states, and it clearly shows that the crystal symmetry degrades to D4hby the isotropic biaxial stress involved in the Cu2O thin‐crystals.