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Suppression of charge ordering across the spin-Peierls transition in TMTTF based Q1D material 13 C NMR spectra and 1/T 1 of (TMTTF) 2 AsF 6 Shigeki Fujiyama Inst. for Molecular Science (Dept. of Applied Physics, UT and CREST-JST) in collaboration with T. Nakamura (Okazaki)

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Suppression of charge ordering across the spin-Peierls transition in TMTTF based Q1D material


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suppression of charge ordering across the spin peierls transition in tmttf based q1d material

Suppression of charge ordering across the spin-Peierls transition in TMTTF based Q1D material

13C NMR spectra and 1/T1 of (TMTTF)2AsF6

Shigeki Fujiyama

Inst. for Molecular Science

(Dept. of Applied Physics, UT and CREST-JST)

in collaboration with T. Nakamura (Okazaki)

charge ordering in 1 4 filled 1dim system

V : intersite Coulomb repuslion

Charge ordering in 1/4 filled 1dim. system

1) para-

1/4 filled

2)

4kF-CDW

Seo, Fukuyama

4kF-BCDW

Mazumdar

Clay

Campbell

3)

low t phase diagram
Low T phase diagram

Coexistence of CO and sP.

(Also indicated by IR/Raman)

High-field spectra

PF6 (sP)

Physical ‘touching’ destroys charge ordering.

this talk
This talk
  • 13C NMR spectra / Nuclear spin-lattice relaxation rate 1/T1 for (TMTTF)2AsF6
  • 1) in the paramagnetic state
  • 2) below (in the vicinity of ) spin-Peierls transition
  • to pursue the development of charge ordering.
  • A1) Development of CO is demonstrated succesfully.
  • (only one spin correlation function)
  • A2) Reduction of CO amplitude at TSP.
  • (CO is not a necessary condition for sP transition)
13 c nmr spectra of tmttf 2 asf 6
13C NMR spectra of (TMTTF)2AsF6

TSP

TCO

Charge ordering at 102 K is

confirmed, and the center of gravity

of the spectra is unchanged at TCO.

nuclear spin lattice relaxation rate 1 t 1
Nuclear spin-lattice relaxation rate 1/T1

The ratio of charge densities

between charge accepting

and donating sites is 2:1.

TCO

Only one spin correlation func.

and opening of a pseudogap

to differentiate charge densities.

shifts in the vicinity of spin peierls transition

TSP

TSP

Dw

Shifts in the vicinity of spin-Peierls transition

Charge ordering is suppressed

at the spin-Peierls transition

temperature.

(if charge ordering would have

survived in the SP state....)

1 t 1 in the vicinity of sp transition
1/T1 in the vicinity of sP transition

cf)

Spin-Peierls transition in this material seems to be 1st order.

summary 13 c nmr study of tmttf 2 asf 6
Summary(13C NMR study of (TMTTF)2AsF6)

Below TCO, only one spin correlation func. and pseudogap behavior to differentiate charge densities.

Charge ordering (4kF-CDW) is confirmed at 102 K.

Charge ordering is suppressed at TSP possibly due to considerable electron-lattice coupling. This naturally leads to competitive interplay between 4kF-CDW and spin-Peierls instability. The low T electronic state is located in the vicinity of the critical point between CO and non-CO.

souces for discrepancies between ucla
Souces for discrepancies between UCLA
  • Different strategies to access the sP state.
  • Different sample and amplitude of CO (2:1 in my study and 3:1 in UCLA)
  • Inherent problem in NMR for TMTTF salts
  • Comparable spin shift and chemical shift with opposite signs in the b-c plane.
  • Alternating transfer integrals (dimerization of molecules) (This favours bond ordering.)
charge ordering in 1 4 filled 1dim system15

V : intersite Coulomb repuslion

Charge ordering in 1/4 filled 1dim. system

1) para-

1/4 filled

2)

4kF-CDW

Seo, Fukuyama

3)

4kF-BCDW

Mazumdar

Clay

Campbell