Instabilities of Weyl loop semimetals

Abstract

We study Weyl-loop semi-metals with short range interactions, focusing on the possible interaction driven instabilities. We introduce an ò expansion regularization scheme by means of which the possible instabilities may be investigated in an unbiased manner through a controlled weak coupling renormalization group (RG) calculation. The problem has enough structure that a 'functional' RG calculation (necessary for an extended Fermi surface) can be carried out analytically. The leading instabilities are identified, and when there are competing degenerate instabilities a Landau-Ginzburg calculation is performed to determine the most likely phase. In the particle-particle channel, the leading instability is found to be to a fully gapped chiral superconducting phase which spontaneously breaks time reversal symmetry, in agreement with general symmetry arguments suggesting that Weyl loops should provide natural platforms for such exotic forms of superconductivity. In the particle hole channel, there are two potential instabilities-to a gapless Pomeranchuk phase which spontaneously breaks rotation symmetry, or to a fully gapped insulating phase which spontaneously breaks mirror symmetry. The dominant instability in the particle hole channel depends on the specific values of microscopic interaction parameters.

Magnetotransport properties of the single-crystalline nodal-line semimetal candidatesCaTX(T=Ag,Cd;X=As,Ge)

“…For example, the weak dispersion of the drumhead surface states leads to a large density of states near the Fermi level. Therefore, possible interaction-induced instabilities on the surface of nodal-line semimetals have been widely discussed in theory [12][13][14] .…”

Quantum critical scaling of gapped phases in nodal-line semimetals

“…whereas the mass term m φ is not renormalized and can be set to zero at the fixed point, which corresponds to a quantum phase transition. We also note that the polarization bubble in the CDW, SC and SDW channels has explicit frequency dependence, and is distinct from earlier works that studied the effect of Coulomb interactions in the Yukawa language by decomposing the four fermion interaction in the Hartree channel [34,51]. In the Coulomb case, the bosonic propagator is frequency independent, implying in the absence of renormalization of the fermionic wavefunction.…”

Fate of superconductivity in disordered Dirac and semi-Dirac semimetals

“…In addition, Weyl SM (WSM), in which the low-energy fermionic excitations display linear dispersion around pairs of nodes with opposite chirality, was observed in TaAs, NbAs, TaP, and NbP by the angle-resolved photoemission spectroscopy (ARPES) [10][11][12][13][14]. There also exist other types of SMs, such as 3D nodal line SM (NLSM) [15][16][17][18], 2D semi-DSM , 3D double-WSM [47][48][49][50][51][52][53][54][55][56][57][58][59], 3D triple-WSM [49,53,[56][57][58][59][60][61][62], 3D anisotropic-WSM [49,[63][64][65], and 3D Luttinger SM [66][67][68][69][70].…”

“…The difference is owing to the fact that the fermion DOS vanishes at zero energy, namely ρ(0)=0. Cooper pairing instability may be achieved in other SMs, including 2D semi-DSM [43,44], 3D DSM [96], 3D WSM [97,98], 3D NLSM [17,18], and 3D Luttinger SM [67,69,70]. In these materials, there is also a threshold value for the strength of attraction.…”