arXiv subjects

Risako Kikuchi

Publications and source records attributed to Risako Kikuchi.

6 recordsLinked to original sources

arXiv2026

Thermoelectric enhancement from an asymmetric spectral-conductivity cusp in spin-1 chiral fermions

A recent study showed that, in spin-1 chiral fermion systems composed of two linearly dispersing bands and one trivial band, impurity scattering produces an asymmetric cusp in the spectral conductivity. We demonstrate that this asymmetric cusp markedly enhances the electronic thermoelectric response. Using linear-response theory within the self-consistent Born approximation, we find low-temperature enhancements in both the Seebeck coefficient and the electronic figure of merit. Increasing the curvature of the trivial band further strengthens this cusp-induced enhancement, even though the corresponding density of states becomes smoother. To clarify this mechanism, we introduce a minimal cusp model for the spectral conductivity and show that the enhancement is most pronounced when the cusp is sharp and strongly asymmetric, and when the spectral conductivity at the cusp energy is small.

cond-mat.mes-hall↗

arXiv2025

Cusped Electrical Conductivity in Spin-1 Chiral Fermion Systems Arising from Multifold Band Degeneracy

The energy-dependent electrical conductivity in spin-1 chiral fermion systems with disorder is studied using the self-consistent Born approximation. A distinct cusp-like feature appears at an energy different from the band-crossing point, arising from the multifold band-crossing structure formed by the Dirac and trivial bands. The energy position of the cusp and the corresponding value of the electrical conductivity are found to depend sensitively on both the impurity scattering strength and the curvature of the trivial band. These findings demonstrate the critical role of multifold band crossings and disorder-induced broadening of energy levels in determining the transport properties, offering theoretical insight into the unconventional conductivity behavior observed in topological semimetals hosting spin-1 chiral fermions.

cond-mat.mes-hall↗

arXiv2024

Band Curvature Effects on Quantum Transport of Spin-1 Chiral Fermion Systems

We theoretically investigate the quantum transport properties of three-dimensional spin-1 chiral fermion systems with a curved trivial band. In the multiband system with two distinct characters--a linear Dirac band and a quadratic trivial band--the hybridization induced by impurity effects leads to pronounced energy and temperature dependences in the electrical conductivity. We show that the conductivity is suppressed by the trivial band in the low-energy regime near the threefold degenerate point and enhanced in the band-crossing point of the Dirac and trivial bands. These results are derived using the self-consistent Born approximation within the framework of linear response theory.

cond-mat.mes-hall↗

arXiv2023

Electrical conductivity and screening effect of spin-1 chiral fermions scattered by charged impurities

We theoretically study the quantum transport in a three-dimensional spin-1 chiral fermion system in the presence of coulomb impurities based on the self-consistent Born approximation. We find that the flat-band states anomalously enhance the screening effect, and the electrical conductivity is increased in the low-energy region. It is also found that reducing the screening length leads to an increase in the forward scattering contribution and, thus, an increase in the vertex correction in the high-energy region.

cond-mat.mes-hall↗

arXiv2023

Quantum Transport in Spin-1 Chiral Fermion: Self-Consistent Born Approximation

Quantum transport for a spin-1 chiral fermion is studied within the self-consistent Born approximation. We find characteristic properties around zero energy, i.e., the peak structure of the density of states and significant suppression of electrical conductivity. These structures originate from the flat band and its interband effect.

cond-mat.mes-hall↗

arXiv2022

Quantum transport of a spin-1 chiral fermion

We theoretically study the quantum transport in a three-dimensional spin-1 chiral fermion system in the presence of impurity scattering. Within the self-consistent Born approximation, we find peak structure of the density of states and significant suppression of electrical conductivity around the zero energy. The zero-energy conductivity depends less on impurity concentration, unlike a Weyl fermion. These properties originate from the flat band structure of spin-1 chiral fermion.

cond-mat.mes-hall↗