Hall coefficient and magnetoresistance in boson+fermion dimer models for the pseudogap phase of high Tc superconductors

TL;DR

This paper models the pseudogap phase of high Tc superconductors using a boson+fermion dimer framework, predicting a temperature-dependent sign change in the Hall coefficient linked to coupling sign reversal, with implications for magnetoresistance behavior.

Contribution

It introduces a novel explanation for the Hall coefficient sign change in the pseudogap phase based on coupling sign reversal in a boson+fermion dimer model, connecting it to experimental observations.

Findings

Hall coefficient changes sign at a characteristic temperature proportional to the cyclotron frequency.

The sign change is due to the coupling between fermionic dimers and magnetic field switching sign.

Magnetoresistance vanishes to order B^2 at the temperature where the Hall coefficient crosses zero.

Abstract

We show that the Hall coefficient of the boson+fermion dimer model for the pseudogap phase of high temperature superconductivity introduced in Punk et al. changes sign from negative at low temperatures to positive at high temperatures at a characteristic temperature scaling proportional to the the cyclotron frequency of the fermionic dimers (divided by k), (here k~0.7 fits the experimental data well). We show that this is an effect of the changing of the sign of the coupling between the fermionic dimer and the magnetic field from negative coupling -e at low temperatures to positive coupling +e at high temperature, with the Hall coefficient being proportional to R_H~e_B*e_E*e_J (the product of the magnetic charge, electric charge and current charge all of which we carefully define). We relate the Hall conductivity to the coefficient in Kohler's like rule for magnetoconductivity and calculate some corrections which are relevant near the intermediate temperature range ~50K (typical values for the cyclotron frequency of the dimers). Furthermore we make a sharp prediction that the magnetoresistance effect vanishes to order B^2 at the temperature and magnetic field where the Hall coefficient vanishes.