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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

High-pressure properties of TTF–QBr2I2 crystal at low temperatures.(a) Hydrostatic pressure dependence of the relative permittivity at 5 K, ɛr (T=5 K) on a TTF–QBr2I2 crystal (filled squares) in comparison with a quantum (anti)ferroelectric DMTTF–QBr4 crystal (filled circles, redrawn based on data in ref. 29). The inset shows the inverse permittivity obeying a simple power law, ɛr (T=5 K)∝/p–pc/–1, as expected for quantum ferroelectricity. (b) Electric polarization (P) versus electric field (E) hysteresis loops with a triangular a.c. electric field at T=4 K and frequency f=1 kHz.
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f4: High-pressure properties of TTF–QBr2I2 crystal at low temperatures.(a) Hydrostatic pressure dependence of the relative permittivity at 5 K, ɛr (T=5 K) on a TTF–QBr2I2 crystal (filled squares) in comparison with a quantum (anti)ferroelectric DMTTF–QBr4 crystal (filled circles, redrawn based on data in ref. 29). The inset shows the inverse permittivity obeying a simple power law, ɛr (T=5 K)∝/p–pc/–1, as expected for quantum ferroelectricity. (b) Electric polarization (P) versus electric field (E) hysteresis loops with a triangular a.c. electric field at T=4 K and frequency f=1 kHz.

Mentions: The permittivity at the lowest temperature ɛr (T=5 K) as a function of pressure reveals a divergent-like sharp maximum at pc (Fig. 4a). There are some similarities and dissimilarities in the quantum critical behaviour near the QCP between the present case and the pressure-induced antiferroelectric NIT of DMTTF–QBr4 (ref. 29). Despite the very similar crystal structures in the paraelectric state, the inverse-ɛr versus p plot (inset to Fig. 4a) indicates the different behaviour between the two crystals around the QCP; in TTF–QBr2I2, the permittivity increases much more rapidly, obeying a simple power law of ɛr (T=5 K)∝/p–pc/–1. Because the maximum ɛr (T=5 K) of TTF–QBr2I2 (∼800) is four times as large as that of DMTTF–QBr4 (<200), these observations reflect the different nature, that is, ferroelectric versus antiferroelectric, of the pressure-induced ordered phases. This difference manifests itself in structural changes.


Quantum ferroelectricity in charge-transfer complex crystals.

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

High-pressure properties of TTF–QBr2I2 crystal at low temperatures.(a) Hydrostatic pressure dependence of the relative permittivity at 5 K, ɛr (T=5 K) on a TTF–QBr2I2 crystal (filled squares) in comparison with a quantum (anti)ferroelectric DMTTF–QBr4 crystal (filled circles, redrawn based on data in ref. 29). The inset shows the inverse permittivity obeying a simple power law, ɛr (T=5 K)∝/p–pc/–1, as expected for quantum ferroelectricity. (b) Electric polarization (P) versus electric field (E) hysteresis loops with a triangular a.c. electric field at T=4 K and frequency f=1 kHz.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: High-pressure properties of TTF–QBr2I2 crystal at low temperatures.(a) Hydrostatic pressure dependence of the relative permittivity at 5 K, ɛr (T=5 K) on a TTF–QBr2I2 crystal (filled squares) in comparison with a quantum (anti)ferroelectric DMTTF–QBr4 crystal (filled circles, redrawn based on data in ref. 29). The inset shows the inverse permittivity obeying a simple power law, ɛr (T=5 K)∝/p–pc/–1, as expected for quantum ferroelectricity. (b) Electric polarization (P) versus electric field (E) hysteresis loops with a triangular a.c. electric field at T=4 K and frequency f=1 kHz.
Mentions: The permittivity at the lowest temperature ɛr (T=5 K) as a function of pressure reveals a divergent-like sharp maximum at pc (Fig. 4a). There are some similarities and dissimilarities in the quantum critical behaviour near the QCP between the present case and the pressure-induced antiferroelectric NIT of DMTTF–QBr4 (ref. 29). Despite the very similar crystal structures in the paraelectric state, the inverse-ɛr versus p plot (inset to Fig. 4a) indicates the different behaviour between the two crystals around the QCP; in TTF–QBr2I2, the permittivity increases much more rapidly, obeying a simple power law of ɛr (T=5 K)∝/p–pc/–1. Because the maximum ɛr (T=5 K) of TTF–QBr2I2 (∼800) is four times as large as that of DMTTF–QBr4 (<200), these observations reflect the different nature, that is, ferroelectric versus antiferroelectric, of the pressure-induced ordered phases. This difference manifests itself in structural changes.

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