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Quantum ferroelectricity in charge-transfer complex crystals.

Horiuchi S, Kobayashi K, Kumai R, Minami N, Kagawa F, Tokura Y - Nat Commun (2015)

Bottom Line: Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4-n bromine substituents (QBr4-nIn, n=0-4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF).Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral-ionic transition compounds, such as well-known ferroelectric complex of TTF-QCl4 and quantum antiferroelectric of dimethyl-TTF-QBr4.By contrast, TTF-QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition.

View Article: PubMed Central - PubMed

Affiliation: 1] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan [2] CREST, Japan Science and Technology Agency (JST), Tokyo 102-0076, Japan.

ABSTRACT
Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4-n bromine substituents (QBr4-nIn, n=0-4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF-QBr2I2 exhibits a ferroelectric neutral-ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral-ionic transition compounds, such as well-known ferroelectric complex of TTF-QCl4 and quantum antiferroelectric of dimethyl-TTF-QBr4. By contrast, TTF-QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition.

No MeSH data available.


Related in: MedlinePlus

Chemical and crystal structures of tetrathiafulvalene (TTF) complexes of tetrahalo-p-benzoquinones (QBr4–nIn).(a) Chemical form of QBr4–nIn. (b-e) Molecular packings of the TTF–QBr4–nIn complexes. (b) Neutral (TTF)2(QBr2I2) projected along the c direction. (c) Ionic 1:1 TTF–QBr3I projected along the a direction. (d,e) Neutral 1:1 TTF–QBr2I2 projected along the crystallographic a and b directions. For clarity, the halogen positions of the QBr2I2 molecules are shown only for preferable occupations.
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f1: Chemical and crystal structures of tetrathiafulvalene (TTF) complexes of tetrahalo-p-benzoquinones (QBr4–nIn).(a) Chemical form of QBr4–nIn. (b-e) Molecular packings of the TTF–QBr4–nIn complexes. (b) Neutral (TTF)2(QBr2I2) projected along the c direction. (c) Ionic 1:1 TTF–QBr3I projected along the a direction. (d,e) Neutral 1:1 TTF–QBr2I2 projected along the crystallographic a and b directions. For clarity, the halogen positions of the QBr2I2 molecules are shown only for preferable occupations.

Mentions: To search for the QCP accompanied by quantum ferroelectricity, tetrahalo-p-benzoquinones of variable molecular volume are ideal for inducing structural changes with least perturbations to the electron affinities. In fact, the NIT has been demonstrated through optical spectra of two neutral TTF–QI4 complexes of different stoichiometries (1:1 and 2:1) under a modest pressure of ∼2–3 GPa232425. In this study, we prepared tetrahalo-p-benzoquinones with n iodine and 4–n bromine substituents (QBr4–nIn, n=0–4; Fig. 1a) to examine the stepwise change in the lattice volume and to modify the NIT of TTF–QI4 and the ferroelectric SP of TTF–QBr4. In this family, we have realized the ideal NIT type quantum ferroelectricity (TTF–QBr2I2) by tuning the applied hydrostatic pressure


Quantum ferroelectricity in charge-transfer complex crystals.

Horiuchi S, Kobayashi K, Kumai R, Minami N, Kagawa F, Tokura Y - Nat Commun (2015)

Chemical and crystal structures of tetrathiafulvalene (TTF) complexes of tetrahalo-p-benzoquinones (QBr4–nIn).(a) Chemical form of QBr4–nIn. (b-e) Molecular packings of the TTF–QBr4–nIn complexes. (b) Neutral (TTF)2(QBr2I2) projected along the c direction. (c) Ionic 1:1 TTF–QBr3I projected along the a direction. (d,e) Neutral 1:1 TTF–QBr2I2 projected along the crystallographic a and b directions. For clarity, the halogen positions of the QBr2I2 molecules are shown only for preferable occupations.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4490386&req=5

f1: Chemical and crystal structures of tetrathiafulvalene (TTF) complexes of tetrahalo-p-benzoquinones (QBr4–nIn).(a) Chemical form of QBr4–nIn. (b-e) Molecular packings of the TTF–QBr4–nIn complexes. (b) Neutral (TTF)2(QBr2I2) projected along the c direction. (c) Ionic 1:1 TTF–QBr3I projected along the a direction. (d,e) Neutral 1:1 TTF–QBr2I2 projected along the crystallographic a and b directions. For clarity, the halogen positions of the QBr2I2 molecules are shown only for preferable occupations.
Mentions: To search for the QCP accompanied by quantum ferroelectricity, tetrahalo-p-benzoquinones of variable molecular volume are ideal for inducing structural changes with least perturbations to the electron affinities. In fact, the NIT has been demonstrated through optical spectra of two neutral TTF–QI4 complexes of different stoichiometries (1:1 and 2:1) under a modest pressure of ∼2–3 GPa232425. In this study, we prepared tetrahalo-p-benzoquinones with n iodine and 4–n bromine substituents (QBr4–nIn, n=0–4; Fig. 1a) to examine the stepwise change in the lattice volume and to modify the NIT of TTF–QI4 and the ferroelectric SP of TTF–QBr4. In this family, we have realized the ideal NIT type quantum ferroelectricity (TTF–QBr2I2) by tuning the applied hydrostatic pressure

Bottom Line: Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4-n bromine substituents (QBr4-nIn, n=0-4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF).Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral-ionic transition compounds, such as well-known ferroelectric complex of TTF-QCl4 and quantum antiferroelectric of dimethyl-TTF-QBr4.By contrast, TTF-QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition.

View Article: PubMed Central - PubMed

Affiliation: 1] National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8562, Japan [2] CREST, Japan Science and Technology Agency (JST), Tokyo 102-0076, Japan.

ABSTRACT
Quantum phase transition achieved by fine tuning the continuous phase transition down to zero kelvin is a challenge for solid state science. Critical phenomena distinct from the effects of thermal fluctuations can materialize when the electronic, structural or magnetic long-range order is perturbed by quantum fluctuations between degenerate ground states. Here we have developed chemically pure tetrahalo-p-benzoquinones of n iodine and 4-n bromine substituents (QBr4-nIn, n=0-4) to search for ferroelectric charge-transfer complexes with tetrathiafulvalene (TTF). Among them, TTF-QBr2I2 exhibits a ferroelectric neutral-ionic phase transition, which is continuously controlled over a wide temperature range from near-zero kelvin to room temperature under hydrostatic pressure. Quantum critical behaviour is accompanied by a much larger permittivity than those of other neutral-ionic transition compounds, such as well-known ferroelectric complex of TTF-QCl4 and quantum antiferroelectric of dimethyl-TTF-QBr4. By contrast, TTF-QBr3I complex, another member of this compound family, shows complete suppression of the ferroelectric spin-Peierls-type phase transition.

No MeSH data available.


Related in: MedlinePlus