Anomalous density fluctuations in a random $t$-$J$ model

TL;DR

This paper investigates a disordered $t$-$J$ model with density interactions, identifying a new fixed point with anomalous density fluctuations relevant to electron spectroscopy, but finds it unstable compared to a known fixed point.

Contribution

It extends the $t$-$J$ model to include density-density interactions and analyzes the resulting fixed points and density fluctuation exponents.

Findings

Discovered a new fixed point at non-zero density interaction strength $K$.

Found the new fixed point to be unstable towards the $K=0$ fixed point.

Calculated the density fluctuation exponents relevant for electron energy-loss spectroscopy.

Abstract

A previous work (Joshi et al., arXiv:1912.08822) found a deconfined critical point at non-zero doping in a $t$-$J$ model with all-to-all and random hopping and spin exchange, and argued for its relevance to the phenomenology of the cuprates. We extend this model to include all-to-all and random density-density interactions of mean-square strength $K$. In a fixed realization of the disorder, and for specific values of the hopping, exchange, and density interactions, the model is supersymmetric; but, we find no supersymmetry after independent averages over the interactions. Using the previously developed renormalization group analysis, we find a new fixed point at non-zero $K$. However, this fixed point is unstable towards the previously found fixed point at $K=0$ in our perturbative analysis. We compute the exponent characterizing density fluctuations at both fixed points: this exponent determines the spectrum of electron energy-loss spectroscopy.