Unusual magnetic quantum oscillations in organic metals at high magnetic fields

Abstract

We report on Shubnikov+le Haas (SdH) and de Haa.s-van Alphen (dHvA) results for the highly two-dimensional (2D) organic superconductors K-(ET)z13(T. = 3.5 K) and~"-(ET)zSF5CH2CFzS03 (TC= 4.4 K). The SdH oscillations of both materials show an apparent deviation from the well-understood 2D dHvA signal at low temperatures and high magnetic fields. For IC-(ET)213, the mechanism leading to this behavior still needs to be clarified. For fl"-(ET)zSF~CH2CF2SOS, an anomaloussteadybackground part of the magnetoresistanceseems to accountfor the observeddiscrepancies. PACS: 74.70.Kn; 72. 15.Gd Keywords:Organic superconductors,Fermisurface,magnetotransport electronic structure [1]. These charge-transfer salts 1. Introduction are available as high-quality crystals enabling the detection of well-developed de Haas-van Alphen The organic metals and superconductors of the (dHvA) and Shubnikov4e Haas (SdH) oscillations type (ET)2X, where X represents a monovalent anion [2]. Thereby, the dHvA signals are well understood and ET (= BEDT-TTF) is the organic donor either by the conventional 3D Lifshitz-Kosevich molecule bisethylenedithio-tetrathiafulvalene, are (LK) theory [3] or by 2D theoretical models [4,5]. characterized by their quasi-two-dimensional (2D) Pronounced 2D dHvA oscillations are realized at

Spin-zero anomaly in the magnetic quantum oscillations of a two-dimensional metal

“…In addition to the standard LK theory the latter term contains the factor I ( p) that takes into account such effects as interlayer hopping [12,31] or the dispersion of magnetic-breakdown bands [13,32]. (For β -(BEDT-TTF) 2 SF 5 CH 2 CF 2 SO 3 , however, magnetic breakdown is irrelevant as has been shown by SdH measurements up to 60 T [33]). Important consequences of (6) are deviations from the usual LK temperature and magnetic-field dependences.…”

Conducting Organic Radical Cation Salts with Organic and Organometallic Anions

“…A field-modulation technique was employed in order to gain higher field resolution and Early on 102 it was already recognized that the background magnetoresistance underlying the SdH oscillations was anomalous in that its temperature and field dependence was more characteristic of a nonmetal, unlike all other organic conductors where oscillations had been observed. The dHvA and SdH measurements were extended 103,104 to higher fields in a special cantilever device that allowed the simultaneous recording of both magnetic torque (proportional to B 2 dM/dB) and magnetoresistance. The simultaneous measurement was essential to extract the correct background resistance in order to derive the anomalous SdH oscillations.…”

de Haas–van Alphen oscillations in the quasi-two-dimensional organic conductorκ−(ET)2Cu(NCS)Gvozdikov1, Pershin2, Steep3 et al. 2002Phys. Rev. B352340View full textAdd to dashboardCite

“…The quasi-two-dimensional ͑quasi-2D͒ ET salts form the largest organic superconductor family with unusual normal and superconducting properties [1][2][3][4][5][6] which come out of the layered structure as well as the specific shape of the Fermi surface. In this paper we report our experimental results on de Haas-van Alphen oscillations in the organic compound -(ET) 2 Cu(NCS) 2 and give their theoretical explanation based on the coherent magnetic breakdown approach.…”