Negative Impurity Magnetic Susceptibility and Heat Capacity in a Kondo Model with Narrow Peaks in the Local Density of Electron States

TL;DR

This paper investigates how peaks in the electron density of states near the Fermi energy affect the magnetic susceptibility and heat capacity in a Kondo model, revealing potential negative values and a novel decrease upon adding magnetic impurities.

Contribution

It introduces the effect of narrow peaks in the density of states on impurity thermodynamics, predicting negative susceptibility and heat capacity changes in a Kondo system.

Findings

Magnetic susceptibility and heat capacity can be negative.

Addition of magnetic impurities can decrease these quantities in nonmagnetic samples.

Predicted effects are potentially observable experimentally.

Abstract

Temperature dependencies of the impurity magnetic susceptibility, entropy, and heat capacity have been obtained by the method of numerical renormalization group and exact diagonalization for the Kondo model with peaks in the electron density of states near the Fermi energy (in particular, with logarithmic Van Hove singularities). It is shown that these quantities can be {\it negative}. A new effect has been predicted (which, in principle, can be observed experimentally), namely, the decrease in the magnetic susceptibility and heat capacity of a nonmagnetic sample upon the addition of magnetic impurities into it.