Kleeorin Yaakov, Meir Yigal
Department of Physics, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel.
The Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva, 84105, Israel.
Sci Rep. 2018 Jul 12;8(1):10539. doi: 10.1038/s41598-018-28822-y.
Observing quantum phase transitions in mesoscopic systems is a daunting task, thwarted by the difficulty of experimentally varying the magnetic interactions, the typical driving force behind these phase transitions. Here we demonstrate that in realistic coupled double-dot systems, the level energy difference between the two dots, which can be easily tuned experimentally, can drive the system through a phase transition, when its value crosses the difference between the intra- and inter-dot Coulomb repulsion. Using the numerical renormalization group and the semi-analytic slave-boson mean-field theory, we study the nature of this phase transition, and demonstrate, by mapping the Hamiltonian into an even-odd basis, that indeed the competition between the dot level energy difference and the difference in repulsion energies governs the sign and magnitude of the effective magnetic interaction. The observational consequences of this transition are discussed.
在介观系统中观测量子相变是一项艰巨的任务，这一过程因实验上难以改变磁相互作用（这些相变背后的典型驱动力）而受阻。在此，我们证明，在实际的耦合双量子点系统中，两个量子点之间的能级差在实验上易于调节，当其值跨越点内和点间库仑排斥能之差时，可驱动系统发生相变。利用数值重整化群和半解析的 slave-boson 平均场理论，我们研究了这一相变的性质，并通过将哈密顿量映射到奇偶基矢上证明，确实是量子点能级差与排斥能差之间的竞争决定了有效磁相互作用的符号和大小。我们还讨论了这一相变的观测结果。
