2015/05/20 by Yanagisawa, Takashi · 1 citation
#FOS: Physical sciences #Strongly Correlated Electrons (cond-mat.str-el)
paper · doi:10.48550/arxiv.1505.05295
We investigate the Kondo effect in Dirac systems, where Dirac electrons interact with the localized spin via the s-d exchange coupling. The Dirac electron in solid state has the linear dispersion and is described typically by the Hamiltonian such as Hk= v\bf k⋅ σ for the wave number \bf k where σj are Pauli matrices. We derived the formula of the Kondo temperature T\rm K by means of the Green's function theory for small J. The T\rm K is determined from a singularity of Green's functions in the form T\rm K≃ Dexp(-\rm const./ρ|J|) when the exchange coupling |J| is small where D=D/√(1+D2/(2μ)2) for a cutoff D and ρ is the density of states at the Fermi surface. When |μ|≪ D, T\rm K is proportional to |μ|: T\rm K≃ |μ|exp(-\rm const./ρ|J|). The Kondo screening will, however, disappear when the Fermi surface shrinks to a point called the Dirac point, that is, T\rm K vanishes when the chemical potential μ is just at the Dirac point. The resistivity and the specific heat exhibit a log-T singularity in the range T\rm K < T≪ |μ|/k\rm B. Instead, for T∼ O(|μ|) or T>|μ|, they never show log-T.