- Email: [email protected]
Hall effect in (DMET)2I3 under pressure
Synthetic Metals, 41--43 (1991) 2167-2170
2167
HALL EFFE~F IN (DMET)_213~NDER PRESSURE
M. ISHIBASHI
Dep. Chem., Tokyo Metropolitan University, Fukazawa, Setagaya-ku, Tokyo 158 (Japan) K. MURATA *Electrotechnical Laboratory, Tsukuba, Ibaraki 305 (Japan) K. KIKUCHI,K. SAITOAND I. |KEMOTO Dep. Chem., Tokyo Metropolitan University, Fukazawa, Setagaya-ku, Tokyo 158 (Japan) K. KOBAYASHI College of Arts and Sciences, the University of Tokyo, Komaba, Megoro-ku, Tokyo 153, (Japan) ABSTRACT The Hall effect under pressure is presented for the quasi one dimensional organic superconductor, (DMET)2I 3. Below 20 -30 K, Hall coefficient decreases from the high temperature almost constant value. Such variation of Hall effect with temperature is discussed comparing with other organic superconductors, such as (DMET)2Au(CN) 2, I~-(BEDT-TTF)2I3 and ~-(BEDTTTF)2Cu(NCS)2 1. INTRODUCTION The superconductivity has been found in eight DMET salts from the discovery in (DMET)2Au(CN)2[1]. The (DMET)2X salts are important when we consider the relation between (TMTSF)2 X salt and (BEDT-TTF)2X salts, where X is the anion[2]. By a suitable choice of anion, we can generate the salts that exhibit electronic properties similar to (TMTTF)2X, (TMTSF)2X and to [~and ~- (BEDT-TTF)2X[3]. The cation molecule DMET is made of half from TMTSF and another half from BEDT-TTF. Among these salts, (DMET)2Au(CN)2 is close to (TMTSF)2X, when we see the temperature-pressure phase diagram[4]; the SDW(spin density wave) at low pressure and low temperature, superconductivity between 1 and 6 kb below 0.9 K. However, the Hall effect is quite different. In TMTSF salts, the sign of the Hall coefficient RH(T) changes only across the phase boundary between metal and SDW[5], while in (DMET)2Au(CN)2, RH(T)starts to de0379-6779/91/$3.50
© Elsevier Sequoia/Printed in The Netherlands
2168
crease from 60 -70 K, which is much above the SDW stabilization temperature, 22- 28 K. However, since the variation of R H ( T ) with temperature accompanying the sing change is suppressed above the pressure, where real SDW disappears, we consider the variation of R H ( T ) with temperature as a phenomena of precursor to SDW[6]. The decrease in R H ( T ) at low temperature has been observed in J3-(BEDTTTF)21317], which is confirmed later[8]. Large temperature dependence of RH(T) at low temperature (60 K) is also observed in ~:-(BEDT-TTF)2Cu(NCS)2 , but the increase to lower temperature[9]. In all of the materials described above, at the temperatures where R H ( T ) changes abruptly, no remarkable change has been observed in the temperature dependence of resistivity, just in the metallic state. Only in ~ : - ( B E D T - T T F ) 2 C u ( N C S ) 2 , at the temperature of the anomaly in RH(T), temperature dependence of the resistivity shows an inflection point[9,10], We pay attention as to whether we observe generally the abrupt change in R H ( T ) at low temperature in the metallic state in those materials that show superconductivity but not SDW. In this paper, we present the Hall effect measurement in (DMET)213, which was first reported in Ref. [11] as a material that show metallic property down to liquid helium temperature. The superconductivity is discovered by us at 0.47 K at P = 0112]. From the preliminary calculation, the band structure of ( D M E T ) 2 A u ( C N ) 2 and (DMET)2I 3 is similar to that of the ( T M T S F ) 2 X salts, i.e. quasi-one dimensional warped Fermi surface. The band structure is more isotropic ( t w o - d i m e n s i o n a l ) in ( D M E T ) 2 I 3 than in (DMET)2Au(CN) 2. 2. EXPERIMENT Experiment was carried out at Electrotechnical laboratory in the same way as described in Ref. [7]. The field direction is perpendicular to the plane. DC current is applied along the most conducting b-axis. Hall effect measurement is only successful under pressure because of the resistance jumps at ambient pressure. 3. RESULT AND DISCUSSION Figure 1 shows a temperature dependence of the resistance at P = 0 and 2 kb. In all temperature ranges below room temperature, metallic behavior is observed. At P = 0 and 1 kb (not shown), superconductivity is observed but not at 2 kb. Figure 2 shows R H ( T ) at 2 and 3.5 kb.
Figure 3 show the results for other
two samples at 3.5 kb. The apparent absolute value for the carrier concentration 1/(e.c.R H ) is about 1 carrier per unit cell, and the apparent mobility I.t = R H .o is 2.2 cm2/V.sec, at 300 K and 52 cm2/V.sec at 50 K, respectively.
2169
As seen from Figs. 2 and 3, there are some sample dependence. Two samples shows a gradual increase in RH(T) with a decrease of temperature down to about 20 - 30 K, below which RH(T) decreases. Below 10 K, RH(T) tums to increase. But one of the sample (#15), the high temperature slope is different from others. Also, in #15, low temperature upturn in RH(T) is not reproduced. At least common feature for all the samples is decrease in RH(T) below 20 - 30 K We examined the resistivity derivative against temperature paying attention to those temperature region. But like the case with [B-(BEDT-TTF)213, no remarkable anomaly is found. The decrease of RH(T) below the the high temperature value can not be explained by the anisotropy dependence of the scattering lifetime due to electron-electron scattering[8]. Since the band structure is quasi-one-dimensional, SDW instability is plausible. Actually, the band structure is qualitatively similar to that of ( D M E T ) 2 A u ( C N ) 2, in which large variation of RH(T) with temperature is observed at temperature above real SDW transition[6], a mechanism for the decrease in RH(T) similar to (DMET)2Au(CN)2 is expected also in (DMET)2I 3. REFERENCES
1. K. Kikuchi, M. Kikuchi, T. Namiki, K. Saito, I. Ikemoto, K. Murata, T.Ishiguro, K. Kobayashi, Chem, Lett,,(1987) 931. 2. K. Murata, K. Kikuchi, T.Takahashi, K.Kobayashi, Y.Honda, K.Saito, K.Kanoda, T.Tokiwa, H. Anzai, T. Ishiguro, I.Ikemoto, Mol, Electronics 4 (1988) 173. 3. K. Kikuchi, K. Murata, K. Saito, K. Kobayashi and I. Ikemoto, St~rin~er Proceedings in Phvsics 51 (1990) 230. 4. Y. Honda, K. Murata, K. Kikuchi, K. Saito, I. Ikemoto and K. Kobayashi, Solid State Common, 71 (1989) 1087. 5. J. E. Kwak, J.E. Schirber, P.M. Chaikin, J.M. Williams, H.H. Wang and L.Y. Chiang, Phys. Rev. Lett, 56 (1986) 972. 6. K. Murata, K. Kikuchi, Y. Honda, T. Komazaki, K. Saito, K. Kobayashi and I. Ikemoto, Springer Proceedings in Physics 51 (1990) 234. 7. K. Murata, M. Ishibashi, Y. Honda, M.Tokumoto, N. Kinoshita and H. Anzai, J. Phys, Soc. Jpn. 58 (1989) 3469. 8. B. Korin-Hamzic, L. Forr6 and J. R. Cooper, Phys. Rev. B41 (1990) 11646. 9. K. Murata, M.Ishibashi, N. A. Fortune, Y. Honda, M. Tokumoto, N. Kinoshita and H. Anzai, preprint(1990, August). 10.L.I. Buravov, A.V. Zvarykina, N.D. Kushch, V.N. Laukhin, V.A. Merzhanov, A.G. Khomenko and E.B. Yagubskii, Zh, Eksn. T~or. Fiz. 95 (1989) 322. 11. M. Zh. Aldoshina, L.O. Atobmyan, L.M.Gol'denberg, O.N. Krasochka, R.N. Lyubovskaya and L.M. Chidekel', DQklady Academii Nauk SSSR (Moscow) 289 (1986) 1140. 12. K. Kikuchi, K. Murata, Y.Honda, T. Namiki, K. Saito, T. Ishiguro, K. Kobayashi and I.Ikemoto, ~I, Phy$, $o¢, Jon. 56 (1987) 3436.
2170 I0 -2 ...... e
. .......,
........ ,
(DMET) 213 #4
~
~
/
10-3 AMBIENT
PRE
..,./
10-4
y
~ 10--5 H
~.J"
wU~
p~..,....~..........,..~-.,.-'
[~
L'.
......,
1 0 - 6
.-"
..
.L"
... '...
2
kbar
LT
"
........
,
1
.
.
.
.
.
.
.
.
10
i
100
TEMPERATURE
(K)
Fig. 1 Temperature dependence (DMET)2I 3 at P = 0 and 3 k b . 3
. . . .
I
. . . .
I
(DNET) 2 1 3 3.5
I
. . . .
l
. . . .
f
#13
kbar
LT
•
J-i
< i-
. . . .
I
'
i
H03
2.0
kbar .
"' j
I
.
. . . .
I
. . . .
I
#14
kbar
l
. . . . . . . .
l
.
.
.
.
.
.
#13
Z
LT
~
I
.
~
.
.
;..
j
" ....
.
I
.
. . . .
I
. . . .
I
,
. "" J" ,,, ,...~.:.:. ];~;: ~ ;?'~'.;j,'~'!'t"::
..
-
•
2
, :
~
•
•• '
' ' .,',,~,:4-~:.-.,-
....
-.-'
..:..'.. •
,
r.,
l
,
i.;:':, ,..... .
-
,
,
,
:
":"
"~ ~
,
'""
:-~ !.~'~",-.:~'... :" .~",~Z': ,.* :-~
P
• t[ . ~:. !.~
. . . .
LT
,. : : . .., .. ~ ..'....~ ;.t" :.., ." ":" .. "
m
'
. . . .
_,., .-,;.?:-. ;:
rr
i <
i
(DNET) 2 1 3
3.5
.~ 3C
. / / c ~ oZ
I
(DNET) 2 1 3
~
,,~'i~:"Y-i::':~;.: :'~ ,.:~;:- "k..~....,.;:: i... .~" ." " '~ ": ".~.: '.~:,'r" "
2
. . . .
2
:...~,.,.....
.
~c 3
. . . .
of
!
"
. " :
.:,......,..:....
• ..+ .'.:".;.T-..v~..W.-...-'.-
- ,.
:i
~ T<
(DNET)213 #15 3.5
kbar
LT
-.:"."
. "
z // ~
v
H // c
~
H
/
50 100 150 TEMPERATURE
200 (K)
250
Fig. 2. Temperature dependence of Hall coefficient in (DMET)2I 3 at P = 2 and 3.5 kb.
50 100 150 TEMPERATURE
200 (K)
250
Fig. 3. Temperature dependence of Hall coefficient in ( D M E T ) 2 I 3 at P = 3.5 kb for other samples for comparison of reproducibility. Always seen is the decrease in RH(T ) below 20 -30 K.
2167
HALL EFFE~F IN (DMET)_213~NDER PRESSURE
M. ISHIBASHI
Dep. Chem., Tokyo Metropolitan University, Fukazawa, Setagaya-ku, Tokyo 158 (Japan) K. MURATA *Electrotechnical Laboratory, Tsukuba, Ibaraki 305 (Japan) K. KIKUCHI,K. SAITOAND I. |KEMOTO Dep. Chem., Tokyo Metropolitan University, Fukazawa, Setagaya-ku, Tokyo 158 (Japan) K. KOBAYASHI College of Arts and Sciences, the University of Tokyo, Komaba, Megoro-ku, Tokyo 153, (Japan) ABSTRACT The Hall effect under pressure is presented for the quasi one dimensional organic superconductor, (DMET)2I 3. Below 20 -30 K, Hall coefficient decreases from the high temperature almost constant value. Such variation of Hall effect with temperature is discussed comparing with other organic superconductors, such as (DMET)2Au(CN) 2, I~-(BEDT-TTF)2I3 and ~-(BEDTTTF)2Cu(NCS)2 1. INTRODUCTION The superconductivity has been found in eight DMET salts from the discovery in (DMET)2Au(CN)2[1]. The (DMET)2X salts are important when we consider the relation between (TMTSF)2 X salt and (BEDT-TTF)2X salts, where X is the anion[2]. By a suitable choice of anion, we can generate the salts that exhibit electronic properties similar to (TMTTF)2X, (TMTSF)2X and to [~and ~- (BEDT-TTF)2X[3]. The cation molecule DMET is made of half from TMTSF and another half from BEDT-TTF. Among these salts, (DMET)2Au(CN)2 is close to (TMTSF)2X, when we see the temperature-pressure phase diagram[4]; the SDW(spin density wave) at low pressure and low temperature, superconductivity between 1 and 6 kb below 0.9 K. However, the Hall effect is quite different. In TMTSF salts, the sign of the Hall coefficient RH(T) changes only across the phase boundary between metal and SDW[5], while in (DMET)2Au(CN)2, RH(T)starts to de0379-6779/91/$3.50
© Elsevier Sequoia/Printed in The Netherlands
2168
crease from 60 -70 K, which is much above the SDW stabilization temperature, 22- 28 K. However, since the variation of R H ( T ) with temperature accompanying the sing change is suppressed above the pressure, where real SDW disappears, we consider the variation of R H ( T ) with temperature as a phenomena of precursor to SDW[6]. The decrease in R H ( T ) at low temperature has been observed in J3-(BEDTTTF)21317], which is confirmed later[8]. Large temperature dependence of RH(T) at low temperature (60 K) is also observed in ~:-(BEDT-TTF)2Cu(NCS)2 , but the increase to lower temperature[9]. In all of the materials described above, at the temperatures where R H ( T ) changes abruptly, no remarkable change has been observed in the temperature dependence of resistivity, just in the metallic state. Only in ~ : - ( B E D T - T T F ) 2 C u ( N C S ) 2 , at the temperature of the anomaly in RH(T), temperature dependence of the resistivity shows an inflection point[9,10], We pay attention as to whether we observe generally the abrupt change in R H ( T ) at low temperature in the metallic state in those materials that show superconductivity but not SDW. In this paper, we present the Hall effect measurement in (DMET)213, which was first reported in Ref. [11] as a material that show metallic property down to liquid helium temperature. The superconductivity is discovered by us at 0.47 K at P = 0112]. From the preliminary calculation, the band structure of ( D M E T ) 2 A u ( C N ) 2 and (DMET)2I 3 is similar to that of the ( T M T S F ) 2 X salts, i.e. quasi-one dimensional warped Fermi surface. The band structure is more isotropic ( t w o - d i m e n s i o n a l ) in ( D M E T ) 2 I 3 than in (DMET)2Au(CN) 2. 2. EXPERIMENT Experiment was carried out at Electrotechnical laboratory in the same way as described in Ref. [7]. The field direction is perpendicular to the plane. DC current is applied along the most conducting b-axis. Hall effect measurement is only successful under pressure because of the resistance jumps at ambient pressure. 3. RESULT AND DISCUSSION Figure 1 shows a temperature dependence of the resistance at P = 0 and 2 kb. In all temperature ranges below room temperature, metallic behavior is observed. At P = 0 and 1 kb (not shown), superconductivity is observed but not at 2 kb. Figure 2 shows R H ( T ) at 2 and 3.5 kb.
Figure 3 show the results for other
two samples at 3.5 kb. The apparent absolute value for the carrier concentration 1/(e.c.R H ) is about 1 carrier per unit cell, and the apparent mobility I.t = R H .o is 2.2 cm2/V.sec, at 300 K and 52 cm2/V.sec at 50 K, respectively.
2169
As seen from Figs. 2 and 3, there are some sample dependence. Two samples shows a gradual increase in RH(T) with a decrease of temperature down to about 20 - 30 K, below which RH(T) decreases. Below 10 K, RH(T) tums to increase. But one of the sample (#15), the high temperature slope is different from others. Also, in #15, low temperature upturn in RH(T) is not reproduced. At least common feature for all the samples is decrease in RH(T) below 20 - 30 K We examined the resistivity derivative against temperature paying attention to those temperature region. But like the case with [B-(BEDT-TTF)213, no remarkable anomaly is found. The decrease of RH(T) below the the high temperature value can not be explained by the anisotropy dependence of the scattering lifetime due to electron-electron scattering[8]. Since the band structure is quasi-one-dimensional, SDW instability is plausible. Actually, the band structure is qualitatively similar to that of ( D M E T ) 2 A u ( C N ) 2, in which large variation of RH(T) with temperature is observed at temperature above real SDW transition[6], a mechanism for the decrease in RH(T) similar to (DMET)2Au(CN)2 is expected also in (DMET)2I 3. REFERENCES
1. K. Kikuchi, M. Kikuchi, T. Namiki, K. Saito, I. Ikemoto, K. Murata, T.Ishiguro, K. Kobayashi, Chem, Lett,,(1987) 931. 2. K. Murata, K. Kikuchi, T.Takahashi, K.Kobayashi, Y.Honda, K.Saito, K.Kanoda, T.Tokiwa, H. Anzai, T. Ishiguro, I.Ikemoto, Mol, Electronics 4 (1988) 173. 3. K. Kikuchi, K. Murata, K. Saito, K. Kobayashi and I. Ikemoto, St~rin~er Proceedings in Phvsics 51 (1990) 230. 4. Y. Honda, K. Murata, K. Kikuchi, K. Saito, I. Ikemoto and K. Kobayashi, Solid State Common, 71 (1989) 1087. 5. J. E. Kwak, J.E. Schirber, P.M. Chaikin, J.M. Williams, H.H. Wang and L.Y. Chiang, Phys. Rev. Lett, 56 (1986) 972. 6. K. Murata, K. Kikuchi, Y. Honda, T. Komazaki, K. Saito, K. Kobayashi and I. Ikemoto, Springer Proceedings in Physics 51 (1990) 234. 7. K. Murata, M. Ishibashi, Y. Honda, M.Tokumoto, N. Kinoshita and H. Anzai, J. Phys, Soc. Jpn. 58 (1989) 3469. 8. B. Korin-Hamzic, L. Forr6 and J. R. Cooper, Phys. Rev. B41 (1990) 11646. 9. K. Murata, M.Ishibashi, N. A. Fortune, Y. Honda, M. Tokumoto, N. Kinoshita and H. Anzai, preprint(1990, August). 10.L.I. Buravov, A.V. Zvarykina, N.D. Kushch, V.N. Laukhin, V.A. Merzhanov, A.G. Khomenko and E.B. Yagubskii, Zh, Eksn. T~or. Fiz. 95 (1989) 322. 11. M. Zh. Aldoshina, L.O. Atobmyan, L.M.Gol'denberg, O.N. Krasochka, R.N. Lyubovskaya and L.M. Chidekel', DQklady Academii Nauk SSSR (Moscow) 289 (1986) 1140. 12. K. Kikuchi, K. Murata, Y.Honda, T. Namiki, K. Saito, T. Ishiguro, K. Kobayashi and I.Ikemoto, ~I, Phy$, $o¢, Jon. 56 (1987) 3436.
2170 I0 -2 ...... e
. .......,
........ ,
(DMET) 213 #4
~
~
/
10-3 AMBIENT
PRE
..,./
10-4
y
~ 10--5 H
~.J"
wU~
p~..,....~..........,..~-.,.-'
[~
L'.
......,
1 0 - 6
.-"
..
.L"
... '...
2
kbar
LT
"
........
,
1
.
.
.
.
.
.
.
.
10
i
100
TEMPERATURE
(K)
Fig. 1 Temperature dependence (DMET)2I 3 at P = 0 and 3 k b . 3
. . . .
I
. . . .
I
(DNET) 2 1 3 3.5
I
. . . .
l
. . . .
f
#13
kbar
LT
•
J-i
< i-
. . . .
I
'
i
H03
2.0
kbar .
"' j
I
.
. . . .
I
. . . .
I
#14
kbar
l
. . . . . . . .
l
.
.
.
.
.
.
#13
Z
LT
~
I
.
~
.
.
;..
j
" ....
.
I
.
. . . .
I
. . . .
I
,
. "" J" ,,, ,...~.:.:. ];~;: ~ ;?'~'.;j,'~'!'t"::
..
-
•
2
, :
~
•
•• '
' ' .,',,~,:4-~:.-.,-
....
-.-'
..:..'.. •
,
r.,
l
,
i.;:':, ,..... .
-
,
,
,
:
":"
"~ ~
,
'""
:-~ !.~'~",-.:~'... :" .~",~Z': ,.* :-~
P
• t[ . ~:. !.~
. . . .
LT
,. : : . .., .. ~ ..'....~ ;.t" :.., ." ":" .. "
m
'
. . . .
_,., .-,;.?:-. ;:
rr
i <
i
(DNET) 2 1 3
3.5
.~ 3C
. / / c ~ oZ
I
(DNET) 2 1 3
~
,,~'i~:"Y-i::':~;.: :'~ ,.:~;:- "k..~....,.;:: i... .~" ." " '~ ": ".~.: '.~:,'r" "
2
. . . .
2
:...~,.,.....
.
~c 3
. . . .
of
!
"
. " :
.:,......,..:....
• ..+ .'.:".;.T-..v~..W.-...-'.-
- ,.
:i
~ T<
(DNET)213 #15 3.5
kbar
LT
-.:"."
. "
z // ~
v
H // c
~
H
/
50 100 150 TEMPERATURE
200 (K)
250
Fig. 2. Temperature dependence of Hall coefficient in (DMET)2I 3 at P = 2 and 3.5 kb.
50 100 150 TEMPERATURE
200 (K)
250
Fig. 3. Temperature dependence of Hall coefficient in ( D M E T ) 2 I 3 at P = 3.5 kb for other samples for comparison of reproducibility. Always seen is the decrease in RH(T ) below 20 -30 K.