Quantum oscillations in dual-layered quasi-two-dimensional organic metal (ET) 4 HgBr 4 (C 6 H 4 Cl 2 )
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ONIC PROPERTIES OF SOLID
Quantum Oscillations in Dual-Layered Quasi-Two-Dimensional Organic Metal (ET)4HgBr4(C6H4Cl2) R. B. Lyubovskiia,b, S. I. Pesotskiia,b*, G. V. Shilova, E. I. Zhilyaevaa, A. M. Flakinaa, and R. N. Lyubovskayaa a Institute
of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia b International Laboratory of High Magnetic Fields and Low Temperatures, Wroclaw, 52-421 Poland *e-mail: [email protected] Received September 18, 2015
Abstract—The behavior of de Haas–van Alfven (dHvA) and Shubnikov–de Haas (ShdH) quantum oscillations in dual-layered quasi-two-dimensional organic metal (ET)4HgBr4(C6H4Cl2) is investigated. The oscillation spectra qualitatively agree with theoretical calculations of the bandgap structure. The angular dependence of the oscillation amplitude of magnetoresistance contains “spin zeros”; the analysis of the location of these zeros allows one to evaluate the electron–phonon interaction constant: λ ≈ 0.2. DOI: 10.1134/S1063776116060157
1. INTRODUCTION Conventional quasi-two-dimensional organic metals represent single-crystal samples of cation–radical salts synthesized on the basis of the ET (bis(etilendito)tetratiafulvalen) molecule and its derivatives. During the synthesis, layered samples are formed in which cation layers consisting of ET molecules and possessing metallic conductivity along a layer alternate with insulating anion layers [1–3]. Thus, as a result, one obtains a well-pronounced layered organic metal with anisotropy of about 103–10 4 between the conductivities along and across the layers. In conventional organic metals, the molecular and electronic structures of cation layers are identical or almost identical. This leads to the same Fermi surface (FS) for all cation layers. In this case, the total FS for the entire reciprocal lattice has the form of a cylinder with the axis perpendicular to the metal layers [1–3]. The quasi-twodimensional organic metal (ET)4HgBr4(C6H4Cl2) belongs to a new class of layered conductors, the socalled dual-layered organic metals [4]. In materials of this class, the electronic and molecular structures of neighboring cation layers differ from each other; i.e., the properties of a cation layer, in particular, the FS, are translated through a layer. Such a configuration may have different variants. Neighboring cation layers may be metals with different FSs; in addition, metal and dielectric layers and metal and semimetal layers may be neighbors of each other [4]. In [5], the authors investigated the structure and properties of the duallayered quasi-two-dimensional organic metal (ET)4CoBr4(C6H4Cl2), which is isostructural to
(ET)4HgBr4(C6H4Cl2) at least at temperatures below 280 K [4]. The analysis of X-ray data has shown that there are two different alternating cation layers with different types of packing of ET molecules in this metal. The calculation of the bandgap structure established that one of the layers with α-type is a small-gap insulator whose bandgap width does not exceed the acc
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