# Metal to Orthogonal Metal Transition

## TL;DR

This paper constructs and analyzes a 2D lattice model demonstrating a quantum phase transition from a normal metal to an orthogonal metal, a non-Fermi-liquid state with unique electronic and magnetic properties, using sign-free quantum Monte Carlo simulations.

## Contribution

It introduces an exactly solvable lattice model with fermionic and bosonic fields coupled to $ ext{Z}_2$ gauge fields, revealing a novel quantum phase transition to an orthogonal metal.

## Key findings

- Transition from a normal metal to an orthogonal metal with no Fermi surface.
- Orthogonal metal exhibits non-Fermi-liquid behavior yet responds to magnetic probes like a Fermi liquid.
- Model provides a theoretical framework for understanding exotic quantum metallic states.

## 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 $\mathbb Z_2$ 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 $\mathbb Z_2$ 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.