Theoretical studies of magnetic impurity effects in Dirac electron systems

2015 Fiscal Year Final Research Report

• Project/Area Number: 26800171
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics I
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Shirakawa Tomonori 国立研究開発法人理化学研究所, 創発物性科学研究センター, 研究員 (40571237)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: 磁性不純物 / ディラック電子系 / 密度行列繰り込み群法 / 電子相関 / 近藤効果

Outline of Final Research Achievements

We have introduced a numerical technique to study the general impurity problems using the density-matrix renormalization group method. The method has been applied to the effective models for (a) a single adatom on graphene, (b) a substitutional impurity in graphene, and (c) a single carbon vacancy in graphene. We have found that the ground state of the model (i) behaves as an isolated magnetic impurity in a parameter region, while the ground state of the other two models forms a spin-singlet state where the impurity moment is screened by the conduction electrons. We have also established the ground state phase diagram for model (a) in a wide parameter region including the particle-hole asymmetric case, and we have clarified the relation between the impurity quantum phase transition and the entanglement spectrum for the ground state in this system.

Free Research Field

数物系科学