Emergent QCD Kondo effect in two-flavor color superconducting phase

Abstract

We show that effective coupling strengths between ungapped and gapped quarks in the twoflavor color superconducting (2SC) phase are renormalized by logarithmic quantum corrections. We obtain a set of coupled renormalization-group (RG) equations for two distinct effective coupling strengths arising from gluon exchanges carrying different color charges. The diagram of RG flow suggests that both of the coupling strengths evolve into a strong-coupling regime as we decrease the energy scale toward the Fermi surface. This is a characteristic behavior observed in the Kondo effect, which has been known to occur in the presence of impurity scatterings via non-Abelian interactions. We propose a novel Kondo effect emerging without doped impurities, but with the gapped quasiexcitations and the residual SU(2) color subgroup intrinsic in the 2SC phase, which we call the "2SC Kondo effect."

QCD Kondo excitons

“…In recent studies, new types of the QCD Kondo effect were proposed: the QCD Kondo effect in strong magnetic fields [45] and the QCD Kondo effect induced by the gapped quark in the two-flavor color superconductor [56]. They suggest that the QCD Kondo effect can emerge in various environments relating to the strong interaction.…”

Kondo effect with Wilson fermions

“…Such "relativistic" Kondo effects can occur in relativistic-fermion systems including impurities, such as graphene (see Ref. [6] for a review), Dirac/Weyl semimetals [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], dense nuclear matter [24][25][26][27], and dense quark matter [13,24,[28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44]. Among them, the QCD Kondo effect [24,28] is induced by the color exchange interaction between a light quark and an impurity quark, which is based on quantum chromodynamics (QCD).…”

Heavy-quark spin polarization induced by the Kondo effect in a magnetic field

“…In fact, it was shown that the Kondo effect arises in nuclear matter when Σ c and Σ * c baryons or D and D * mesons exist as impurities, where the spin and/or isospin exchange serves as the non-Abelian interaction [3,[5][6][7]. In addition, many works on Kondo effect in a relativistic system have been done in the literatures [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In this way, the interdisciplinary study bridging condensedmatter physics and QCD/hadron physics focused on the Kondo effect is attracting attention.…”