Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 42: Other Transport Topics

TT 42.1: Vortrag

Mittwoch, 11. März 2026, 09:30–09:45, HSZ/0105

Enhancement of the thermopower of Anderson impurity by Van Hove singularities in graphene nanoribbons — •Damian Krychowski and Krzysztof Wójcik — Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań, Poland

We present results from the numerical renormalization group theory of spin-1/2 ad-atom coupled to contacts made of zigzag graphene nanoribbons (ZGNRs). We propose tuning ZGNRs with a transverse electric field [1] and back gates such that they exhibit one of their asymmetric power-law Van Hove singularities at the Fermi level. We demonstrate that, under these conditions, the local spectral density of the ad-atom spin exhibits a sharp and asymmetric pseudo-gap despite complete Kondo screening. This ensures weak charge conductance and a large Seebeck coefficient at low and moderate temperatures, leading to a high figure of merit over a wide temperature range and impurity energy level. A similar enhancement of the Seebeck coefficient is observed in magic-angle twisted bilayer graphene with a highly particle-hole asymmetric band, though it occurs at a different energy scale [2]. At a set temperature, the sign of thermopower of Kondo-correlated system can be further tuned by dragging the singularity through the Fermi level with gate voltage.

[1] Y.-W. Son, M. L. Cohen and S. G. Louie, Nature 347, 444 (2006).
[2] A. K. Paul et al., Nat. Phys. 18, 691 (2022).

Keywords: Kondo state; Van-Hove singularity; Numerical Renormalization Group; graphene nanoribbons; Seebeck effect