In this work, we study the quantum transition taking place when titanium phthalocyanine molecules are adsorbed on a copper’s surface. Submitted to thermal annealing, depending on the way in which the molecule is adsorbed, this system can be characterized by a Kondo ground state, giving rise to a zero bias peak in the differential conductance. To clarify this new property, derived from the annealing process, we propose a model Hamiltonian that describes the essential physics involved. We show that the Kondo ground state appears as a consequence of the broken symmetry introduced by the annealing. It is not due to an increase of the molecule–substrate interactions but to the modification of the intermolecular lobe orbital matrix elements. This rearrangement rules the entrance of charge into the molecule and provides the conditions for the establishment of the Kondo state. Our results for the differential conductance, corresponding to the electronic current between a STM tip and one of the molecular lobes, agree with the experimental differential conductance measurements. It presents an Abrikosov–Suhl–Kondo resonance at the Fermi level for the configuration where the molecule is distorted. The results obtained within the model we propose, when compared with the experiments, give quantitative support to our interpretation.

中文翻译：

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吸附在 Cu(110) 金属表面上的扭曲钛酞菁分子的近藤效应

在这项工作中，我们研究了钛酞菁分子吸附在铜表面时发生的量子跃迁。进行热退火后，根据分子吸附的方式，该系统可以通过近藤基态来表征，从而在微分电导中产生零偏置峰。为了阐明这一源自退火过程的新特性，我们提出了一个哈密顿量模型来描述所涉及的基本物理原理。我们证明近藤基态的出现是由于退火引起的对称性破缺的结果。这不是由于分子-底物相互作用的增加，而是由于分子间叶轨道矩阵元素的改变。这种重排规则了电荷进入分子并为近藤态的建立提供了条件。我们的微分电导结果（对应于 STM 尖端和分子叶之一之间的电子电流）与实验微分电导测量结果一致。它在费米能级上呈现出分子扭曲构型的 Abrikosov-Suhl-Kondo 共振。与实验相比，我们提出的模型中获得的结果为我们的解释提供了定量支持。