Oscillation Phenomena on the Magnetoresistance of the Organic Superconductor K‐(BEDT‐TTF)₂I₃

Abstract

High-field magnetotransport properties of single crystal samples of the quasi-two-dimensional organic compound K-(BEDT-TTF),I, are investigated at low temperatures in magnetic fields up to 12 T. Pronounced quantum oscillations of the magnetoresistance (Shubnikov-de Haas effect) are observed in magnetic fields above 8 T. In the magnetic field orientation perpendicular to the high conducting b-c plane four different SdH oscillations with fundamental fields 570, 2710, 3280, and 3850T are detected. The corresponding extremal areas of the cross sections of the Fermi surface are found to be in good agreement with theoretical band structure calculations. For the first time "giant" angular oscillations of the magnetoresistivity are observed in r-(BEDT-TTF),I,. These oscillations are periodic in tan 0 in agreement with the quasi-classical explanation by Yamaji. From the experimental data the electronic parameter n/ak, N 0.58 can be estimated.Es werden die Magnetotransport-Eigenschaften von Einkristallen der quasi-zweidimensionalen organischen Verbindung r-(BEDT-TTF),I, bei tiefen Temperaturen in Magnetfeldern bis 12 T untersucht. In Magnetfeldern oberhalb 8 T werden ausgepriigte Quantenoszillationen des Magnetowiderstandes (Shubnikov-de Haas-EKekt) beobachtet. In der Magnetfeldorientierung senkrecht zur hochleitenden b-c-Ebene konnen vier unterschiedliche SdH-Oszillationen mit den Fundamentalfeldern 570, 27 10, 3280 und 3850 T nachgewiesen werden. Die zugehorigen Extremal-Querschnitte der Fermi-Oberflache stimmen mit theoretischen Bandstrukturberechnungen gut uberein. Erstmalig werden ,,gigantkche" Oszillationen in den Winkelabhangigkeiten des Magnetowiderstandes an K-(BEDT-TTF),I, beobachtet. Diese Oszillationen sind in Ubereinstimmung mit der halbklassischen Erklarung von Yamaji periodisch in tan 0. Aus den experimentellen Ergebnissen kann der elektronische Parameter n/ak, % 0,58 abgeschatzt werden.found to be superconductors with a quite high critical temperature T, (up t o 12.8 K in K-(ET)~CU[N(CN),]CI at 0.3 x 10' Pa [l]).

Fermi surface properties of the bifunctional organic metal κ−(BETS)2Mn[N(CN)2]Zverev1, Biberacher2, Oberbauer3 et al. 2019Phys. Rev. B8020View full textAdd to dashboardCite

“…The corresponding peak in the FFT spectrum is at F α = 1135 T, revealing a cyclotron orbit area of 10.83 nm −2 or 27.1% of the Brillouin zone area. This agrees fairly well with the size of the While not predicted by band structure calculations, a small MB gap between the open sheets and cylindrical Fermi surface has also been found in SdH experiments on several other κ-type salts of BETS and BEDT-TTF with a center-symmetric layer structure [32][33][34][35][36][37][38][39]. One can consider a weak, 1 meV, spin-orbit interaction as a possible source of the gap [40].…”

Coherent versus incoherent interlayer transport in layered metals

“…12,13 The in-plane Fermi surfaces have been mapped out in detail utilizing angular-dependent magnetoresistance oscillations ͑AMRO͒. 14,15 The origins of these oscillations were first explained by Yamaji 16 assuming a corrugated 3D Fermi-surface cylinder. If this corrugation (ϰt c ) indeed exists and if it is large enough, beats of the magnetic quantum oscillations are expected.…”

“…14 and fits the assumption of an almost circular in-plane Fermi surface with k F ϭk B max ϭconst. In that case k F is given by k F ϭ(2eF/ប) 1/2 ϭ3.43ϫ10 9 m Ϫ1 , with the well-known dHvA frequency of the so-called ␤ orbit of Fϭ3870 T. 6,8,9,12,14 As mentioned, the bare observation of an AMRO signal is no proof for a 3D Fermi surface. Indeed, for -(BEDT-TTF) 2 I 3 no nodes in the dHvA and SdH signals are visible with oscillations of the ␤ orbit starting at about B min ϭ2.8 T. 9 This means that the maximum dHvA-frequency difference is ⌬Fϭ(3/4)B min ϭ2.1 T. 20 Consequently, the estimated corrugation amplitude should be less than t c Ϸ16 eV, since ⌬F/Fϭ4t c /⑀ F with the Fermi energy ⑀ F ϭប 2 k F 2 /2m* and the effective mass m* ͓ϭ3.9 m e for -(BEDT-TTF) 2 I 3 ͔.…”

“…Similar AMRO data with smaller amplitude at T = 1.6 K have been reported earlier. 14 The maxima of the oscillations are given by…”

Fermi surface properties of the bifunctional organic metal $κ$-(BETS)$_2$Mn[N(CN)$_2$]$_3$ near the metal--insulator transition

“…While not predicted by band structure calculations, a small MB gap between the open sheets and cylindrical Fermi surface has also been found in SdH experiments on several other κ-type salts of BETS and BEDT-TTF with a center-symmetric layer structure [32][33][34][35][36][37][38][39]. One can consider a weak, < ∼ 1 meV, spin-orbit interaction as a possible source of the gap [40].…”