The ground-state energy of a quantum impurity model can be calculated using the numerical renormalization group with a modified discretization scheme, with sufficient accuracy to reliably extract physical information about the system. The approach is applied to study binding of magnetic adsorbates modeled by the Anderson-Newns model for chemisorption on metal surfaces. The correlation energy is largest in the valence-fluctuation regime; in the strong-coupling (Kondo) regime the Kondo-singlet formation energy is found to be only a minor contribution. As an application of the method to more difficult surface-science problems, we study the binding energy of a magnetic atom adsorbed near a step edge on a surface with a strongly modulated surface-state electron density. The zero-temperature magnetic susceptibility is determined from the field dependence of the binding energy, thereby providing an independent result for the Kondo temperature TK, which agrees very well with the TK extracted from a thermodynamic calculation.
Spin susceptibility of Anderson impurities is a key quantity in understanding the physics of Kondo screening. Traditional numerical renormalization group (NRG) calculation of the impurity contribution $χ_{\textrm{imp}}$ to susceptibility, defined originally by Wilson in a flat wide band, has been generalized before to structured conduction bands. The results brought about non-Fermi-liquid and diamagnetic Kondo behaviors in $χ_{\textrm{imp}}$, even when the bands are not gapped at the Fermi energy. Here, we use the full density-matrix (FDM) NRG to present high-quality data for the local suscept…
Simultaneous quantization of bulk conduction and valence states through adsorption of nonmagnetic impurities on Bi2Se3
将拓扑绝缘体Bi 2 Se 3的（111）表面暴露于一氧化碳导致在角分辨光电发射中观察到的特征的强烈移位。该行为非常类似于经常报道的表面的“老化”效应，并且可以得出结论，这种老化最有可能是由于其余气体分子的吸附。光谱变化也类似于最近报道的磁性吸附原子Fe的吸附。所有的光谱变化都可以用导带和价带态的同时限制来解释。这是唯一可能的，因为不寻常的体电子结构的Bi2Se3。价带量子化导致光谱特征类似于狄拉克点处的带隙开口的光谱特征。
Ground States and Excitations of Magnetic Impurities in Pseudogap Superconducting Systems
Donostia International Physics Center (DIPC)（多诺斯蒂亚国际物理中心）；Ikerbasque, Basque Foundation for Science（伊克拉巴斯克，巴斯克科学基金会）；Department of Physics and Nanoscience Center, University of Jyväskylä（于韦斯屈莱大学物理与纳米科学中心）
Line tension in wetting processes is of high scientific and technological relevance, but its understanding remains vague, mainly because of its difficult determination. A widely used method to extract the line tension relies on the variation of a droplet's contact angle with the droplet's size. This approach yields the apparent line tension, which factors in numerous contributions to the finite-size dependence, thus masking the actual line tension in terms of the excess free energy of the three-phase contact line. Based on our recent computer simulation study, we investigate how small amounts …
Position-dependent tight-binding model for Li impurities in monolayer and bilayer graphene
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)（阿根廷国家科学研究委员会）；Instituto de Investigaciones en Fisicoquímica de Córdoba (INFIQC)（科尔多瓦物理化学研究所）；Universidad Nacional de Córdoba, Facultad de Ciencias Químicas（科尔多瓦国立大学理学院）；Instituto de Física Enrique Gaviola (IFEG-CONICET)（恩里克·加维亚多物理研究所）；FaMAF, Universidad Nacional de Córdoba（科尔多瓦国立大学数学、物理学和化学学院）
We study the Ruderman-Kittel-Kasuya-Yosida interaction between magnetic impurities embedded in $p$-doped transition metal dichalcogenide triangular flakes. The role of underlying symmetries is exposed by analyzing the interaction as a function of impurity separation along zigzag and armchair trajectories, in specific parts of the sample. The large spin-orbit coupling in these materials produces strongly anisotropic interactions, including a Dzyaloshinskii-Moriya component that can be sizable and tunable. We consider impurities hybridized to different orbitals of the host transition-metal and i…
We employ {\it{ab-initio}} calculations to investigate the charge density waves in single-layer NbSe$_2$, and we explore how they are affected by transition metal atoms. Our calculations reproduce the observed orthorhombic phase in single-layer NbSe$_2$ in the clean limit, establishing the energy order between three different distorted structures, two consisting of triangular Nb-Nb clusters and a third, energetically unfavoured, consisting of hexagonal Nb-Nb clusters. Such energy order, in agreement with known experimental work, is reversed by the adsorption of Co and Mn, which favour the form…
Using the framework of the density-matrix renormalization group (DMRG), we study a quantum dot coupled to a superconducting nanowire with strong Rashba spin-orbit coupling. Regarding the singlet-to-doublet "0-$π$" transition that takes place when the Kondo effect is overcome by the superconducting gap, we show that the Rashba coupling modifies the critical values at which the transition occurs, favouring the doublet phase. In addition, using a generalized Haldane's formula for the Kondo temperature $T_K$, we show that it is lowered by the Rashba coupling. We benchmark our DMRG results comparin…
