Electron correlation and two dimensionality in the spin-density-wave phase of (TMTTF)$_2$Br under pressure

TL;DR

This study investigates how pressure and magnetic fields influence the spin-density-wave phase in (TMTTF)$_2$Br, revealing the roles of electron correlation and two-dimensionality consistent with mean-field theory predictions.

Contribution

It provides experimental validation of mean-field theory predictions on SDW behavior under pressure, emphasizing the impact of two-dimensionality and electron correlation in (TMTTF)$_2$Br.

Findings

SDW transition temperature increases with magnetic field above 0.5 GPa

Quadratic field dependence of $T_{SDW}$ with pressure-dependent coefficient

SDW transition explained by reduction of coupling constant $N(0)I$ under pressure

Abstract

The incommensurate spin-density-wave (SDW) phase in (TMTTF)$_2$Br was investigated through transport measurements under pressure and magnetic fields parallel to the $c^{\ast}$ axis. For the incommensurate SDW phase of (TMTTF)$_2$Br stabilized above 0.5 GPa, the SDW transition temperature $T_{\rm SDW}$ increases with the applied magnetic field. The field dependence of $T_{\rm SDW}$ is described by a quadratic behavior and the coefficient of the quadratic term increases with increasing pressure. These results are consistent with the prediction of the mean-field theory based on the suppression of the SDW transition by two-dimensionality. From the relation between the coefficient of the quadratic term and $T_{\rm SDW}$ at zero magnetic field, we determined the role of electron correlation and two dimensionality in the SDW phase of (TMTTF)$_2$Br under pressure and found that the SDW transition in (TMTTF)$_2$Br can be well explained within the mean field theory by taking into account the reduction of the coupling constant $N(0)I$ by pressure.