Generalized susceptibility of quasi-one dimensional system with periodic potential: model for the organic superconductor (TMTSF)$_2$ClO$_4$

TL;DR

This paper analytically and numerically investigates the magnetic susceptibility and nesting vectors in a quasi-one-dimensional system with a periodic potential, providing insights into the behavior of organic superconductor (TMTSF)$_2$ClO$_4$.

Contribution

It introduces a detailed analysis of the susceptibility and nesting vectors considering the effect of periodic potential, revealing new constraints on the potential's magnitude for spin density wave phenomena.

Findings

Susceptibility exhibits a plateau-like maximum in the sweptback region.

The best nesting vector is near but not at the inflection point.

The sweptback region shrinks with increasing periodic potential, disappearing at V ≥ 4 t_b'.

Abstract

The nesting vector and the magnetic susceptibility of the quasi-one-dimensional system having imperfectly nested Fermi surface are studied analytically and numerically. The magnetic susceptibility has the plateau-like maximum in ``\textit{sweptback}'' region in the momentum space, which is surrounded by $\mathbf{Q}=(2 k_F, \pi) + \mathbf{q}_i$ ($k_F$ is the Fermi wave number, $i=1,3,4$, and $\mathbf{q}_1$, $\mathbf{q}_3$ and $\mathbf{q}_{4}$ are given in this paper). The best nesting vector, at which the susceptibility $\chi_0(\mathbf{Q})$ has the absolute maximum at T=0, is obtained near but not at the inflection point, $\mathbf{Q}=(2 k_F, \pi)+\mathbf{q}_4$. The effect of the periodic potential $V$ on the susceptibility is studied, which is important for the successive transitions of the field-induced spin density wave in (TMTSF)$_2$ClO$_4$. We obtain that the sweptback region (surrounded by $\mathbf{q}_2$, $\mathbf{q}_3$ and $\mathbf{q}_4$ when $V>0$) becomes small as $V$ increases and it shrinks to $\mathbf{q}_3$ for $V \geq 4 t_b'$, where $t_b'$ gives the degree of imperfect nesting of the Fermi surface, i.e. the second harmonics of the warping in the Fermi surface. The occurrence of the sign reversal of the Hall coefficient in the field-induced spin density wave states is discussed to be possible only when $V<2 t_b'-2 t_4$, where $t_4$ is the amplitude of the fourth harmonics of the warping in the Fermi surface. This gives the novel limitation for the magnitude of $V$.