Magnetotransport and Fermi-surface topology of β’’-(BEDT-TTF)2AuBr2: The effects of

Abstract

Magnetoresistance measurements have been made on a number of single-crystal samples of the metallic charge-transfer salt P"-(BEDT-TTF}, AuBr"using magnetic fields up to 50 T. The experiments have been carried out for a wide range of orientations of the sample with respect to the magnetic field and for temperatures ranging between 80 mK and 4.2 K. The magnetoresistance exhibits a complex series of Shubnikov -de Haas oscillations, an anisotropic angle dependence, and, below 1 K, hysteresis. Both the hysteresis in the magnetoresistance and frequency mixing effects observed in the Shubnikov -de Haas spectrum can be explained by the effects of Shoenberg magnetic interaction, and this mechanism has been successfully used to model the observed Fourier spectrum of the magnetoresistance. The complex Shubnikov-de Haas frequency spectrum of P"-(BEDT-TTF}zAuBrz is proposed to result from the effects of a spin-density wave on the band structure, which alters the original Fermi surface to produce three two-dimensional carrier pockets. The angle dependence of the Shubnikov-de Haas oscillation amplitudes has been used to deduce the approximate shapes and orientations of these pockets, which are found to be in good qualitative agreement with the proposed model.

Quasi-two-dimensional organic superconductors: A review

“…In the β ′′ and λ phases the predicted bandstructure seems very sensitive to the choice of basis set, and the disagreement between calculation and measurement is often most severe (see e.g. [26,27,28,29]). …”

Oscillatory magnetoresistance in the charge-transfer saltβ′′-(BEHouse1, Harrison2, Blundell3 et al. 1996Phys. Rev. BSelf Cite564260View full textAdd to dashboardCite

“…2,3,8 In this paper we have used magnetoresistance measurements in pulsed fields of up to 60 T and the observation of angle-dependent magnetoresistance oscillations in static fields to demonstrate that the charge-transfer salt ␤Љ-͑BEDT-TTF͒ 2 AuBr 2 undergoes a field-driven transition between two different SDW ground states. ␤Љ-͑BEDT-TTF͒ 2 AuBr 2 is a particularly interesting material, exhibiting a variety of apparent magnetic phase transitions below 30 K. [9][10][11] Furthermore, the low-temperature magnetoresistance of typical samples possesses a complex dependence on field strength and orientation, 9 plus a rich spectrum of SdH and dHvA oscillations. [9][10][11] These have proved difficult to reconcile with the various predicted Fermi surfaces, which either consist of quasi-one-dimensional ͑Q1D͒ sheets or a single closed Q2D pocket plus a Q1D section ͓see Fig.…”

Magneto-transport properties in the density wave phase of β′′-(BEDT-TTF)2CsCd(SCN)4

“…Based on the above results, the hump-like anomalies below 32 K in the temperature dependence of the interlayer resistance should be ascribed to a density wave transition accompanied by the variation of the electronic structure, since I) β''-CsCd has a pair of large one-dimensional Fermi surface, which may be nested and II) Actually, β"-(BEDT-TTF) 2 AuBr 2 [9,10], which has the same molecular arrangement as β''-CsCd, also has a density wave transition although they showed no remarkable anomaly in their resistance measurement [10,11,12].…”