Exotic d-wave Cooper Pair Bose Metal in two dimensions

TL;DR

This paper demonstrates the existence of a Cooper pair Bose metal phase in two-dimensional systems with spin anisotropy, revealing a non-Fermi liquid state with unique pairing properties through advanced computational methods.

Contribution

It introduces the first evidence of a 2D Cooper pair Bose metal phase using quantum Monte Carlo and renormalization group techniques, highlighting the role of spin anisotropy.

Findings

Presence of a nonzero momentum Bose surface in the pair distribution

Observation of $d_{xy}$ pairing correlations

Spin anisotropy influences pairing symmetry

Abstract

The study of non-Fermi liquids sheds light on unconventional phenomena in condensed matter systems that lie beyond the scope of Landau Fermi liquid theory. One intriguing example is the Bose metal, characterized by an uncondensed bosonic ground state. However, constructing a Bose metal phase in two dimensions (2D) remains a significant challenge.} Utilizing constraint path quantum Monte Carlo and functional renormalization group methods on a fermionic system with spin anisotropy in a 2D lattice, we reveal the emergence of a Cooper pair Bose metal (CPBM) phase in a highly anisotropic regime ($\alpha < 0.30$) with wide range of filling, as proposed in [A. E. Feiguin and M. P. A. Fisher, Phys. Rev. Lett. 103, 025303 (2009)]. Our findings exhibit a visible nonzero momentum Bose surface in the Cooper-pair distribution function, accompanied by a distinct signal of $d_{xy}$ correlation between pairs. Our results highlight that spin-dependent anisotropy in the Fermi surface leads to versatile pairing forms. Platforms such as ultracold atoms in optical lattices and recently proposed altermagnets hold promise for realizing this intriguing phase.