arXiv subjects

Koh-ichi Nittoh

Publications and source records attributed to Koh-ichi Nittoh.

4 recordsLinked to original sources

arXiv2017

Atomic layer doping of Mn magnetic impurities from surface chains at a Ge/Si hetero-interface

We realize Mn $δ$-doping into Si and Si/Ge interfaces using Mn atomic chains on Si(001). Highly sensitive X-ray absorption fine structure techniques reveal that encapsulation at room temperature prevents the formation of silicides / germanides whilst maintaining one dimensional anisotropic structures. This is revealed by studying both the incident X-ray polarization dependence and post-annealing effects. Density functional theory calculations suggest that Mn atoms are located at substitutional sites, and show good agreement with experiment. A comprehensive magnetotransport study reveals magnetic ordering within the Mn $δ$-doped layer, which is present at around 120\,K. We demonstrate that doping methods based on the burial of surface nanostructures allows for the realization of systems for which conventional doping methods fail.

cond-mat.mtrl-sci↗

arXiv2002

Integer- and Non-Integer-Shift of the Chern-Simons Coupling under a Local Higher Covariant Derivative Regulator

The Chern-Simons coupling shift is calculated within the framework of the hybrid regularization based on a local higher covariant derivative regulator. When the Yang-Mills term is present in the theory the well-know integer-shift is obtained, but is absent, the shift value is non-integer. These results show a possibility that a non-integer-shift can be derived using a local higher covariant derivative and also suggest that the Yang-Mills term plays an important role in the integer-shift of the Chern-Simons coupling.

hep-th↗

arXiv2001

Consistency of the Hybrid Regularization with Higher Covariant Derivative and Infinitely Many Pauli-Villars

We study the regularization and renormalization of the Yang-Mills theory in the framework of the manifestly invariant formalism, which consists of a higher covariant derivative with an infinitely many Pauli-Villars fields. Unphysical logarithmic divergence, which is the problematic point on the Slavnov's method, does not appear in our scheme, and the well-known vale of the renormalization group functions are derived. The cancellation mechanism of the quadratic divergence is also demonstrated by calculating the vacuum polarization tensor of the order of $Λ^0$ and $Λ^{-4}$. These results are the evidence that our method is valid for intrinsically divergent theories and is expected to be available for the theory which contains the quantity depending on the space-time dimensions, like supersymmetric gauge theories.

hep-th↗

arXiv2000

A Note on the Quadratic Divergence in Hybrid Regularization

We consider the quadratic divergence of the Yang-Mills theory when we use the hybrid regularization method consisting of the higher covariant derivative terms and the Pauli-Villars fields. By the explicit calculation of the diagrams, we show that the higher derivative terms for the ghost fields are necessary for the complete cancellation of the quadratic divergence.

hep-th↗