Towards artificial Kondo nano-lattice structures

迈向人造近藤纳米晶格结构

• 批准号: 427676771
• 负责人: Professor Dr. Michael Huth
• 金额: --
• 依托单位: Physikalisches Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/427676771?language=en
• 关键词: Towards; artificial; Kondo; nano; lattice

The Kondo effect is a prime example for the physics of correlated electron systems. In general terms, it is the result of the screening of a localized degeneracy coupled to a bath of fermions. In the narrower sense, the Kondo effect involves the formation of a spin singlet below a characteristic Kondo temperature if a magnetic impurity is embedded in a system of conduction electrons.An important open question relates to the nature of the characteristic length scale associated with the Kondo effect. This characteristic length scale or Kondo screening length can be estimated from the electronic energy gain associated with the singlet formation and the Fermi velocity of the conduction electrons. Theoretical estimates find it to be in the range from 10 to 1000 nm for metallic Kondo systems.In this project first steps will be taken towards a systematic study of the nature of the Kondo screening cloud and its associated length scale in nanoscale metallic Kondo systems. For this two complementary approaches are followed.In one approach, metallic Kondo single electron transistors (SET) based on the Kondo system Platinum-Chromium will be fabricated by combining area-selective atomic layer deposition and focused electron beam induced deposition (FEBID). The temperature- dependent low-temperature current-voltage characteristics of the metallic Kondo SETs will shed light on the question whether the formation of a Kondo screening cloud is subject to finite-size renormalization effects.The second approach uses nano-granular metals prepared by FEBID in which metallic nano-grains are dopend with magnetic impurities such as to form the novel material class of granular Kondo metals. Tunneling between the nano-grains may be expected to become coherent at low temperatures and for sufficiently large tunneling rates, such that a coherent, granular Fermi liquid is formed, as has been found in conventional nano- granular metal structures in the strong tunnel coupling regime. Of major scientific relevance will be to understand what the similarities and differences are in comparison with the coherent heavy fermion state known from a large class of intermetallic Ce, Yb or U compounds.

近藤效应是关联电子系统物理的一个典型例子。一般说来，它是局域简并与费米子浴耦合的屏蔽的结果。在狭义意义上，近藤效应是指如果磁性杂质被嵌入到导电电子系统中，在特征近藤温度以下形成自旋单态。一个重要的悬而未决的问题是与近藤效应相关的特征长度标度的性质。这一特征长度标度或近藤屏蔽长度可以从与单态形成相关的电子能量增益和传导电子的费米速度估计出来。理论估计发现，金属近藤系统的屏蔽云在10到1000 nm的范围内。在这个项目中，我们将采取第一步，系统地研究纳米级金属近藤系统中近藤屏蔽云的性质及其相关的长度尺度。对于这两种互补的方法，一种方法将结合区域选择原子层沉积和聚焦电子束诱导沉积(FEBID)来制备基于Kondo系统的金属Kondo单电子晶体管(SET)。金属Kondo集随温度变化的低温电流-电压特性将揭示Kondo屏蔽云的形成是否受到有限尺寸重整化效应的影响。第二种方法使用FEBID制备的纳米颗粒金属，其中金属纳米颗粒掺入磁性杂质，形成新型颗粒状Kondo金属。在低温和足够大的隧穿速率下，纳米颗粒之间的隧穿有望变得相干，从而形成相干的颗粒状费米液体，就像在强隧道耦合区域中在传统的纳米颗粒金属结构中所发现的那样。重大的科学意义将是了解与从一大类金属间化合物Ce、Yb或U中已知的相干重费米子态相比有什么相似和不同之处。