Magneto-oscillations in the high-magnetic-field state of(TMTSF)2ClO

Abstract

We report a systematic study of the anomalous rapid oscillation ͑RO͒ phenomena in the quasi-onedimensional organic metal ͑TMTSF͒ 2 ClO 4 in pulsed magnetic fields up to 51 T. We argue that the temperature and magnetic-field dependence of the RO amplitudes in the high-field state result from the reconstructed, nested Fermi surface topology at low temperatures in high magnetic fields. In this topology, the RO amplitudes depend on competing magnetic breakdown and Bragg reflection probabilities, along with Lifshitz-Kosevich reduction factors. ͓S0163-1829͑96͒01422-1͔Organic conductors based on the TMTSF ͓tetramethyltet-raselenafulvalene͔ molecule are model systems in which to investigate the fundamental physics of low-dimensional electronic systems. 1 When slowly cooled through its anion ordering transition at 24 K, ͑TMTSF͒ 2 ClO 4 exhibits a number of magnetic-field-dependent phases, as shown in the inset of Fig. 1. Here the magnetic field is parallel to the c* axis, the least conducting direction. At ambient pressure ͑TMTSF͒ 2 ClO 4 is a superconductor below 1.3 K and up to 30 mT. A cascade of phase transitions into field-inducedspin-density-wave ͑FISDW͒ phases occurs at fields above 4 T. Near 15 T the second-order FISDW transition temperature reaches a maximum of Ϸ5.5 K. Another phase boundary is present at B RE ϳ28 T, and the high-field state ͑HFS͒ above B RE is also known as the reentrant phase. 2 Recently extensive studies of transport and magnetization have indicated that the B RE line is not connected to the second-order FISDW line, and hence the HFS is not a reentrant metallic state. 3 Aside from the complication of the B RE phase boundary, the HFS strongly represents the final Nϭ0 nested state predicted by the ''standard model. '' 1 As a function of field quantum oscillations, reminiscent of de Haas-van Alphen and Shubnikov-de Haas ͑SdH͒ oscillations seen in conventional metals, are observed in transport, 4-6 thermodynamic, 4,7,8 far-infrared reflectivity, 9 and acoustic 10 properties. In Figs. 1͑a͒ and 1͑b͒ these oscillations are clearly seen, superimposed on the background magnetoresistance, for transport in both the a-axis and c*-axis directions in the title material. However, since the zero-field Fermi surface is open, their origin must arise from some explanation other than quantum oscillations seen in standard closed orbit quasi-two-dimensional metals. Although a number of theories have been proposed for the rapid oscillations 11-15 none are completely consistent, even qualitatively, with all the effects that are observed.In this paper we explore the rapid oscillation ͑also known as ''RO''͒ behavior in the high-field state in ͑TMTSF͒ 2 ClO 4 . Previous pulsed-field studies by Agosta et al. 16 ͑see also Osada et al. 17 ͒ have shown that the more well ordered the sample is ͑the ClO 4 anions order at about 24 K͒, the greater is the ratio of the first-to-second harmonic amplitude, as seen in the Fourier transform ͑FT͒ spectrum. Although the temperature dependence of the FT amplitude of both the first ͑F...

Role of the dimerized gap due to anion ordering in spin-density wave phase of(TMTSF)2ClO4at hi

“…The sudden increase of R 0 and of the RO amplitude is consistent with previous results. 8 On the other hand, by deuteration of the ClO 4 salt, T AO increases from 24 K to 27 K, and the transition field to the first and last semimetallic SDW phase increases from 6.5 T to 7 T and from 8 T to 9.7 T, respectively. In addition, the field of the broad peak shifts to the high field side and the phase boundary at high field β HI is not observed below 28 T. This indicates that deuteration of the ClO 4 salt moves the FISDW phase boundary towards the high pressure side and β HI is pushed out above 28 T. These results are regarded as the consequence of a positive chemical pressure in the crystal FIG.…”

Two rapid oscillations in the magnetoresistance in the field-induced spin-density-wave state of(TMTSF)2ClO4

“…Although there are several recent explanations for the RO in the FISDW, none of them are satisfactory. Recently, Brooks et al 20 suggested that the combination effects of the reconstructed and nested FS, MB, and BR result in closed orbits which causes the conventional SdH or dHvA effects in the HFS above 28 T and below 5.5 K. The temperature and field dependence in this region is explained by the Lifshitz-Kosevich formula with reasonable parameter. Uji et al also ascribed their RO II to dHvA oscillations in the FS reconstructed by the SDW and the AO.…”

“…On the other hand, Brooks et al 20 proposed that the RO in the HFS above 28 T results from the magnetic breakdown ͑MB͒ of the reconstructed, nested FS topology. The temperature and field dependence of the RO is explained with the competation between MB and Bragg reflection ͑BR͒ probabilities, along with Lifshitz-Kosevich reduction factors.…”

Nonperturbative effects of the periodic potential on the field-induced spin-density wave and the sign of the quantum Hall effect in the quasi-one-dimensional conductor(TMTSF)2ClO4

“…The rapid oscillations have been observed in many experiments. 30,31,47 Although some explanations for the rapid oscillations have been proposed [32][33][34][53][54][55][56][57][58][59][60] for the N = 0 phase, the rapid oscillations in the N = 1 phase have not been understood yet.…”