Non-thermal Evidence for Current-Induced Melting of Charge Order in θ-(BEDT-TTF)<sub>2</sub>CsZn(SCN)<sub>4</sub>

Watanabe, Masashi; Yamamoto, Kenichiro; Ito, Takayoshi; Nakashima, Yusaku; Tanabe, Makoto; Hanasaki, N.; Ikeda, Naoshi; Nogami, Yasuyuki; Ohsumi, H.; Toyokawa, H.; Noda, Yukio; Terasaki, Ichiro; Sawano, Fumiaki; Suko, Tomohiro; Mori, H.; Mori, Toshiyuki

doi:10.1143/jpsj.77.065004

Cited by 12 publications

(9 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The optical conductivity and Raman spectra at 6-300 K measured by Suzuki et al 28 also suggest a shortrange charge order of small amplitude. In addition, the 13 C-NMR measurements carried out by Chiba et al 33 indicate that static charge disproportionation develops as temperature decreases below Ϸ140 K but that the disproportionation ratio is reduced again below Ϸ20 K. 13 C-NMR measurements of the CsZn salt were also done by Kodama et al 30 As the temperature is decreased, the spin susceptibility slowly decreases at 20Յ T Յ 300 K but rapidly increases at T Յ 20 K. 34 The Curie-Weiss behavior in the low temperature regime is considered to be intrinsic. The spin concentration is 1% if we assume S =1/ 2 localized spins with 1 B .…”

Section: Previous Experimental Results and Theoriesmentioning

confidence: 98%

“…On the basis of an experimental finding that the intensity of x-ray diffuse scattering corresponding to charge modulation along the c axis decreases with increasing current, they attributed the nonlinearity to current-induced melting of insulating charge-order domains. [12][13][14][15] However, no quantitative explanation of the nonlinear I-V curves has yet been given. In addition, they measured the I-V curves in a relatively high current region ͑10 −7 -10 −2 A͒, which is disadvantageous in terms of self-heating.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite

We have measured the current-voltage ͑I-V͒ characteristics, dielectric properties, and magnetoresistances of insulating layered organic crystals -͑BEDT-TTF͒ 2 MZn͑SCN͒ 4 ͑M =Cs,Rb͒, in which electron-electron Coulomb interactions are considered to induce charge ordering. The in-plane I-V characteristics follow the power law with a large exponent that exceeds 10 in the low-temperature limit. The nonlinear I-V characteristics are attributed to electric field induced unbinding of pairs of an electron and a hole that are thermally excited and attracted to each other due to two-dimensional long-range Coulomb interaction. The temperature and frequency dependences of the in-plane dielectric constant for M = Cs are explained by the polarization of the electron-hole bound pairs, consistently with the I-V characteristics. The large dielectric anisotropy ͑Ϸ100 at 0.6 K͒ observed for M = Cs suggests two-dimensional long-range Coulomb interaction, which is also consistent with the explanation of the nonlinear I-V curves. The organic crystals have a large positive magnetoresistance ratio, e.g., Ϸ10 000% for M = Cs in a magnetic field of 10 T at 0.1 K. The magnetoresistance is nearly independent of the magnetic field orientation despite the highly two-dimensional charge transport, indicating that it is electronspin related. The magnetoresistance may be caused by magnetic field induced parallel alignment of spins of mobile and localized electrons, both in the highest occupied molecular orbital of a BEDT-TTF molecule, and by the resulting suppression of conduction due to the Pauli exclusion principle.

show abstract

Section: Previous Experimental Results and Theoriesmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite

show abstract

“…The x-ray diffuse rods are found at q 1 = (2/3, k, 1/3) and q 2 = (0, k, 1/2) below 120 K [100,101]. This finding implies that a short-range ordered 3a × 3c superlattice (fluctuation of threefold CO) coexists with the 2c superlattice (fluctuation of stripe CO).…”

Section: θ-(Bedt-ttf) 2 X (X = Cszn(scn) 4 I 3 )mentioning

confidence: 84%

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

View full text Add to dashboard Cite

This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF) 2 X, and α-(BEDT-TTF) 2 X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN) 4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I 3 salt. In α-(BEDT-TTF) 2 I 3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ max~0 .6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF) 2 MHg(SCN) 4 (X = NH 4 , K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH 4 salt. α′-(BEDT-TTF) 2 IBr 2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ max~0 .8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. OPEN ACCESSCrystals 2012, 2 1292

show abstract

“…The q 2 -type charge order is believed to compete with another charge order indexed by q 1 = ͑2 / 3,k ,1/ 3͒ at low temperatures in the Cs salt, which was directly observed as two kinds of scattering peaks in x-ray diffraction images at low temperatures. 9 Watanabe et al 10 showed that the suppression of the q 2 peak is not simply due to Joule heating and found a possible nonequilibrium state in a high external current that cannot be achieved in thermal equilibrium. Sawano et al 11 found that the activation energy and the q 2 intensity exhibit the identical current dependence, which strongly suggests that the energy gap seen in the charge transport is the q 2 -type charge order.…”

Section: Introductionmentioning

confidence: 99%

Giant nonlinear conduction from inhomogeneous charge order in rapidly cooledθ−(BEDT-TTF)2RbZn(SCN)

et al. 2009

Self Cite

View full text Add to dashboard Cite

We find a giant nonlinear conduction in the charge-ordered organic salt -͑BEDT-TTF͒ 2 RbZn͑SCN͒ 4 in a rapidly cooled state from 34 to 99 K, which cannot be ascribed to a simple Joule heating. The observed voltage-current characteristics are essentially identical to those of the related organic salt -͑BEDT-TTF͒ 2 CsZn͑SCN͒ 4 , while the energy scale and the working temperatures are 1 order of magnitude higher. Considering that two kinds of charge-ordered domains coexist in this rapidly cooled state, we suggest that the inhomogeneity made of the two charge orders plays an essential role in the giant nonlinear conduction of the -type organic salts.

show abstract

Non-thermal Evidence for Current-Induced Melting of Charge Order in θ-(BEDT-TTF)₂CsZn(SCN)₄

Cited by 12 publications

References 7 publications

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Giant nonlinear conduction from inhomogeneous charge order in rapidly cooledθ−(BEDT-TTF)2RbZn(SCN)

Contact Info

Product

Resources

About

Non-thermal Evidence for Current-Induced Melting of Charge Order in θ-(BEDT-TTF)2CsZn(SCN)4

Cited by 12 publications

References 7 publications

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)Yamaguchi1, Kimata2, Hazama3 et al. 2010Phys. Rev. B245300View full textAdd to dashboardCite

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)Yamaguchi1, Kimata2, Hazama3 et al. 2010Phys. Rev. B245300View full textAdd to dashboardCite

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Giant nonlinear conduction from inhomogeneous charge order in rapidly cooledθ−(BEDT-TTF)2RbZn(SCN)

Contact Info

Product

Resources

About

Non-thermal Evidence for Current-Induced Melting of Charge Order in θ-(BEDT-TTF)₂CsZn(SCN)₄

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite

Charge transport in charge-ordered layered crystalsθ−(BEDT-TTF)2MZn(SCN)
Yamaguchi
¹
,
Kimata
²
,
Hazama
³

et al. 2010
Phys. Rev. B
24
5
30
0
View full text Add to dashboard Cite