Metal to Orthogonal Metal Transition

Abstract

Orthogonal metal [1][2][3] is a new quantum metallic state that conducts electricity but acquires no Fermi surface (FS) or quasiparticles, and hence orthogonal to the established paradigm of Landau's Fermi-liquid (FL). Such state might hold the key of understanding the perplexing experimental observations of quantum metals that are beyond FL -dubbed non-Fermi-liquid (nFL) -ranging from the Cu-and Fe-based oxides [4-7], heavy fermion compounds [8][9][10][11] to the recently discovered twisted graphene heterostructures [12][13][14][15]. However, to fully understand such exotic state of matter, at least theoretically, one would like to construct a lattice model and solve it with unbiased quantum many-body machinery. Here, we achieve this goal by designing a 2D lattice model comprised of fermionic and bosonic matter fields coupled with dynamic Z2 gauge fields, and obtain its exact properties with sign-free quantum Monte Carlo simulations. We find as the bosonic matter fields become disordered, with the help of deconfinement of the Z2 gauge fields, the system reacts with changing its nature from the conventional normal metal with a FS to an orthogonal metal of nFL without FS and quasiparticles and yet still responds to magnetic probe like a FL. Such a quantum phase transition from a normal metal to an orthogonal metal, with its electronic and magnetic spectral properties revealed, is calling for the establishment of new paradigm of quantum metals and their transition with conventional ones.

Designer Monte Carlo simulation for the Gross-Neveu-Yukawa transition

“…We also calculated the conductivity of the Dirac fermions and find its finite frequency scaling behavior consistent with conformal field theory prediction. Our approach provides the promising direction towards the eventual controlled study of fermionic QCPs, and the same concept and principles can be easily generalized to other fermionic QCPs as well, such as the GN chiral XY [42] and Heisenberg [19,23] and the fermion surface coupled to the critical bosons [17] and topological orders [43,44]. Efforts along this line of thinking may help shed new light on key open questions in various fermionic QCPs and may eventually lead to their final solutions.…”

Orthogonal metal in the Hubbard model with liberated slave spins

“…Whereas the f -fermions remain noninteracting in the models of Refs. [31,33,74], the existence of orthogonal phases with residual interactions can readily be conceived.…”

Confinement transition in the QED$_3$-Gross-Neveu-XY universality class

“…Recent work on a system of fermions coupled to a discrete Z 2 gauge field in 2+1 dimensions has demonstrated the existence of such a quantum transition between a deconfined phase with gapless fermionic excitations at weak coupling and a symmetry-broken confined phase with gapped fermionic excitations at strong coupling [9][10][11][12][13]. Systems of gapless fermions coupled to gauge fields with continuous gauge groups are of significant current interest as well.…”