Magneto-oscillations in the high-magnetic-field state of „TMTSF…
2
ClO
4
J. S. Brooks*
Department of Physics, Florida State University, Tallahassee, Florida 32306
R. G. Clark, R. H. McKenzie, R. Newbury, R. P. Starrett, and A. V. Skougarevsky
School of Physics and National Pulsed Magnetic Field Laboratory, University of New South Wales, Sydney, 2052, Australia
M. Tokumoto
Electrotechnical Laboratory, Tsukuba, Ibaraki 305, Japan
S. Takasaki, J. Yamada, and H. Anzai
Himeji Institute of Technology, Akaho-gun, Hyogo 678-12, Japan
S. Uji
National Research Institute for Metals, Tsukuba, Ibaraki 305, Japan
and Department of Physics, Florida State University, Tallahassee, Florida 32306
Received 22 February 1996
We report a systematic study of the anomalous rapid oscillation RO phenomena in the quasi-one-
dimensional organic metal TMTSF
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. S0163-18299601422-1
Organic conductors based on the TMTSF tetramethyltet-
raselenafulvalene molecule are model systems in which to
investigate the fundamental physics of low-dimensional elec-
tronic systems.
1
When slowly cooled through its anion order-
ing transition at 24 K, TMTSF
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
TMTSF
2
ClO
4
is a superconductor below 1.3 K and up to
30 mT. A cascade of phase transitions into field-induced-
spin-density-wave FISDW phases occurs at fields above 4
T. Near 15 T the second-order FISDW transition temperature
reaches a maximum of 5.5 K. Another phase boundary is
present at B
RE
28 T, and the high-field state HFS above
B
RE
is also known as the reentrant phase.
2
Recently exten-
sive 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 bound-
ary, the HFS strongly represents the final N =0 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 SdH oscilla-
tions seen in conventional metals, are observed in
transport,
4–6
thermodynamic,
4,7,8
far-infrared reflectivity,
9
and acoustic
10
properties. In Figs. 1a and 1b these oscil-
lations 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. Al-
though 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 TMTSF
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 K, the greater
is the ratio of the first-to-second harmonic amplitude, as seen
in the Fourier transform FT spectrum. Although the tem-
perature dependence of the FT amplitude of both the first
F 1 265 T and second F 2 530 T harmonics has a
maximum at about 2.1 K within the FISDW phases, about
B
RE
the magnetoresistance and amplitude of F 1 increases
with magnetic field. In the present work, we systematically
investigate the temperature and field dependence of the mag-
netoresistance and RO amplitude above B
RE
in the HFS. We
find the temperature and field dependence of the oscillation
amplitudes bears a strong similarity to the behavior of a sys-
tem with competing magnetic breakdown and Bragg reflec-
tion probabilities, along with the Lifshitz-Kosevich LK re-
duction factors
18
expected for closed orbits in conventional
metals.
The experiments reported here were carried out at the
National Pulsed Magnet Laboratory at the University of New
South Wales.
19
Two samples were studied in a top loading
3
He refrigerator. Both were aligned with the c * axis along
the magnetic field. The voltage and current were along the
c * -axis 125 A and a -axis 180 A directions for the first
and second sample, respectively. The samples were cooled
PHYSICAL REVIEW B 1 JUNE 1996-I VOLUME 53, NUMBER 21
53 0163-1829/96/5321/144065/$10.00 14 406 © 1996 The American Physical Society