Magnetic quantum oscillations in the charge-density-wave state of the organic metals a-(BEDT-TTF)2MHg(SCN)4 with M = K and Tl
M.V. Kartsovnik1, V.N. Zverev2,3, D. Andres1*, W. Biberacher1, T. Helm1**, P.D. Grigoriev4, R. Ramazashvili5, N.D. Kushch6, and H. Müller7
1Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften Walther-Meissner-Strasse 8, Garching D-85748, Germany
2Institute of Solid State Physics, Russian Academy of Sciences Academician Ossipyan Str. 2, Chernogolovka 142432, Russia
3 Moscow Institute of Physics and Technology, Dolgoprudny, Institutskii per. 9, Moscow reg., 141700, Russia
4L.D. Landau Institute for Theoretical Physics, Russian Academy of Sciences Academician Semenov Ave. 1a, Chernogolovka 142432, Russia
5Laboratoire de Physique Théorique – IRSAMC, CNRS and Université de Toulouse UPS, F-31062 Toulouse, France
6Institute of Problems of Chemical Physics, Russian Academy of Sciences Academician Semenov Ave. 1, Chernogolovka 142432, Russia
7European Synchrotron Radiation Facility, Rue Jules Horowitz 6, BP 220, 38043 Grenoble CEDEX 9, France
Received November 23, 2013
The low-temperature charge-density-wave (CDW) state in the layered organic metals α-(BEDT-TTF)2MHg(SCN)4 has been studied by means of the Shubnikov–de Haas and de Haas–van Alphen effects. In addition to the dominant α-frequency, which is also observed in the normal state, both the magnetoresistance and magnetic torque possess a slowly oscillating component. These slow oscillations provide a firm evidence for the CDW-induced reconstruction of the original cylindrical Fermi surface. The α-oscillations of the interlayer magnetoresistance exhibit an anoma-lous phase inversion in the CDW state, whereas the de Haas–van Alphen signal maintains the normal phase. We argue that the anomaly may be attributed to the magnetic-breakdown origin of the α-oscillations in the CDW state. A theoretical model illustrating the possibility of a phase inversion in the oscillating interlayer conductivity in the presence of a spatially fluctuating magnetic breakdown gap is proposed.
PACS: 72.15.Gd Galvanomagnetic and other magnetotransport effects; PACS: 74.70.Kn Organic superconductors; PACS: 71.45.Lr Charge-density-wave systems.
Key words: organic metals, Shubnikov–de Haas effect, de Haas–van Alphen effect, charge-density wave, magnetic breakdown.