Exceptional-torus in strongly correlated nodal-line semimetals with many-body chiral symmetry

Recent studies have revealed a new type of topological phase described by a non-Hermitian (NH) Hamiltonian. In equilibrium systems, if we describe the energy spectrum of quasiparticles having the complex self-energy in terms of effective Hamiltonian, NH physics naturally shows up because of the life time effects from self-energy. The most important point is the emergence of gapless defective points (DPs), which lead to an open Fermi surface, such as Fermi arcs in the bulk energy spectrum.
In previous studies, it is pointed out that the effect of symmetry leads to the symmetry protected NH band touching, such as the symmetry-protected exceptional torus (SPETs). A typical example is a parity-time reversal (PT) symmetric nodal-line semimetal (NLSM).
In this study, we demonstrate how the SPETs can emerge in strongly correlated systems. We analyze correlated NLSM on a diamond lattice model with a sublattice dependent on-site Hubbard interaction by using the dynamical mean-field theory. First, we reveal the emergence of a SPET unique to NH physics with many-body chiral symmetry, which forms the 3D open Fermi surface locked on the Fermi level. We further elucidate that the static susceptibility for a sublattice with weak interaction is enhanced by the emergence of SPETs.