Probing a Bose Metal via Electrons: Inescapable non-Fermi liquid scattering and pseudogap physics

Abstract

Non-Fermi liquid behavior and pseudogap formation are among the most well-known examples of exotic spectral features observed in several strongly correlated materials such as the hole-doped cuprates, nickelates, iridates, ruthenates, ferropnictides, doped Mott organics, transition metal dichalcogenides, heavy fermions, dand f -electron metals, etc. We demonstrate that these features are inevitable consequences when fermions couple to an unconventional Bose metal [1] mean field consisting of lower-dimensional coherence. Not only do we find both exotic phenomena, but also a host of other features that have been observed e.g. in the cuprates including nodal anti-nodal dichotomy and pseudogap asymmetry(symmetry) in momentum(real) space. Obtaining these exotic and heretofore mysterious phenomena via a mean field offers a simple, universal, and therefore widely applicable explanation for their ubiquitous empirical appearance.

Mottness induced superfluid phase fluctuation with increased density

“…Specifically for the cuprates and nickelates, this classically intuitive mechanism explains the robust upper limit of doping level in the entire families of cuprate and nickelate superconductors. Combined with the persistent consistency of optical [21], transport [19,21], quasi-particle (QP) [16,18,20], and superconducting [17] properties of the exact same model with corresponding experimental observations, our results reinforce the notion of a new paradigm that the HT-SC in the cuprates (and likely nickelates) is dominated by physics of bosonic superfluidity, as opposed to pairing-strength limited Cooper pairing. The contents of this paper are organized as follows.…”

“…Furthermore, since it is the same set of bosons the QP scatters against in the non-superfluid and the superfluid phase, the incoherent normal-state scattering rate is trivially proportional to the low-temperature coherent superconducting QP gap [18], explaining the ARPES observed puzzling connection between the incoherent and the coherent features. Specifically in the Bose metal phase that corresponding to the pseudogap phase, scattering against EBL generates a Fermi arc with an obvious pseudogap [20] in the anti-nodal region that fills up (instead of closes) at higher temperature, same as the observations by ARPES and scanning tunneling spectroscopy (STS). For fixed momentum, the resulting pseudogap displays a strong asymmetric gap edge in energy, while for a fixed site it has a perfect symmetric gap edge [20], reconciling the puzzling qualitative inconsistency between ARPES and STS.…”

“…Specifically in the Bose metal phase that corresponding to the pseudogap phase, scattering against EBL generates a Fermi arc with an obvious pseudogap [20] in the anti-nodal region that fills up (instead of closes) at higher temperature, same as the observations by ARPES and scanning tunneling spectroscopy (STS). For fixed momentum, the resulting pseudogap displays a strong asymmetric gap edge in energy, while for a fixed site it has a perfect symmetric gap edge [20], reconciling the puzzling qualitative inconsistency between ARPES and STS.…”

“…Below we revisit several recent studies that demonstrated persistent agreement of optical [21], transport [19,21], QP [16,18,20], and superconducting [17] properties of EBL with corresponding experimental observations. The fact that these successful applications of EBL are all via the same Hamiltonian with the same set of parameters strongly supports the scenario in which charge-related physics in the cuprates can be understood intuitively by a simple EBL.…”

“…Here we show that all these important questions can be answered naturally in the scenario of the emergent Bose liquid (EBL) [16][17][18][19][20][21]. Essentially, the high-energy local Coulomb repulsion that prevents double occupation of carriers in each lattice site at low energy (so-called 'Mottness') leads to a rather large hard core of the superfluid carriers at even lower temperature.…”