In-plane second harmonic wave generation in multiband organic conductors

Abstract

The second harmonic wave(SHW) generation from Joule heating as a heat source in multiband organic conductors with two group of charge carriers, quasi-one dimensional (q1D) and quasi-two dimensional (q2D) has been theoretically studied in the plane of the layers. Such are the series of q2D organic conductors α − (BEDT − TTF)2MHg(SCN)4[M = K, NH4, Rb, Tl] which have attracted considerable attention over the last few years due to two different ground states and rich phenomena associated with them. We consider a case when electric currents, flowing through the conductor are along the most conducting axis, x-axis. The SHW amplitude is analyzed as a function of the magnetic field and the angle between the arbitrary magnetic field and the normal to the plane of the layers. The results are discussed in comparison to the previous work that considers the case of a SHW generated along the least conducting axis, z-axis. We expect our findings to show that the amplitude of the SHW generated in the plane of the layers is much larger than the one of the SHW generated along the direction perpendicular to the layers. The angular oscillations of the wave amplitude are associated with the charge carriers motion on both the cylindrical part and quasi-planar sheets of the Fermi surface in a tilted magnetic field. The changes in the wave amplitude with the field orientation are correlated with the corresponding angular changes in both the electrical and thermal conductivity. We will also investigate the contribution from both the q1D and q2D charge carriers to the observation of the effect. It is expected the group of charge carriers with a q1D energy spectrum to be significantly dominant in the SHW generation in the plane of the layers.