Metal to Orthogonal Metal Transition*

Abstract

Orthogonal metal 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 a state may hold the key of understanding the perplexing experimental observations of quantum metals that are beyond FL, i.e., dubbed non-Fermi-liquid (nFL), ranging from the Cu- and Fe-based oxides, heavy fermion compounds to the recently discovered twisted graphene heterostructures. However, to fully understand such an exotic state of matter, at least theoretically, one would like to construct a lattice model and to 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 that 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 an FS to an orthogonal metal of nFL without FS and quasiparticles and yet still responds to magnetic probe like an 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.

Monte Carlo study of the pseudogap and superconductivity emerging from quantum magnetic fluctuations

“…The development of quantum Monte Carlo (QMC) algorithms for a class of models of this type has created a feasible way to study this physics in an unbiased manner [14][15][16] . In QMC models, FS fermions couple to bosonic fluctuations, representing certain collective modes of low-energy fermions [17][18][19][20][21][22][23]. The bosonic part is bestowed with independent (non-fermionic) dynamics and can be tuned to criticality to mimic the situation in real materials.…”

Identification of non-Fermi liquid fermionic self-energy from quantum Monte Carlo data

“…In particular, it has been found that designer models of fermion-boson models offer a pathway to access fermionic QCPs while avoiding the notorious sign problem in large-scale quantum Monte Carlo (QMC) simulations. Such models have been implemented in several simulations, studying nematic 49,50 , ferromagnetic 51 , antiferromagnetic [52][53][54][55][56] , gauge field [57][58][59][60][61][62] , and Yukawa-SYK-type 41 QCPs. The focusing on a particular soft boson offers an unbiased numerical test for either a Q = 0 or a finite Q analytical theory of metallic quantum criticality.…”

Measuring Rényi entanglement entropy with high efficiency and precision in quantum Monte Carlo simulations

“…To test the efficiency of the Qiu Ku algorithm on systems with topological order, we start with a toy model of Z 2 topological phase on 2d checkerboard lattice [42][43][44], with the following Hamiltonian,…”