Solitons in the Crossover between Band Insulator and Mott Insulator: Application to TTF-Chloranil under Pressure

Fukuyama, Hidetoshi; Ogata, Masao

doi:10.7566/jpsj.85.023702

Cited by 13 publications

(30 citation statements)

References 13 publications

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“…If the N and I phases form dynamical domains by thermal excitations, however, then the mobile NIDWs can carry topological charge current. Thus, the NI crossover at high temperatures offers a region for testing the topological charge transport, as suggested by recent theoretical studies ( 21 ). A decrease in resistivity was reported in two-terminal measurements around this region ( 23 , 25 ).…”

Section: Introductionmentioning

confidence: 85%

Topological charge transport by mobile dielectric-ferroelectric domain walls

et al. 2019

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The concept of topology has been widely applied in condensed matter physics, leading to the identification of peculiar electronic states on three-dimensional (3D) surfaces or 2D lines separating topologically distinctive regions. In the systems explored so far, the topological boundaries are built-in walls; thus, their motional degrees of freedom, which potentially bring about new paradigms, have been experimentally inaccessible. Here, working with a quasi-1D organic material with a charge-transfer instability, we show that mobile neutral-ionic (dielectric-ferroelectric) domain boundaries with topological charges carry strongly 1D-confined and anomalously large electrical conduction with an energy gap much smaller than the one-particle excitation gap. This consequence is further supported by nuclear magnetic resonance detection of spin solitons, which are required for steady current of topological charges. The present observation of topological charge transport may open a new channel for broad charge transport–related phenomena such as thermoelectric effects.

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Section: Introductionmentioning

confidence: 85%

Topological charge transport by mobile dielectric-ferroelectric domain walls

et al. 2019

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“…In Ref. 30, in contrast, the activation energy was considered to be determined by the sum of excitation energies of charge and spin solitons. If we apply these interpretations to the present results across the N-I ferro boundary [ Fig.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…A theoretical analysis of soliton excitations has been performed motivated by these findings. 30 In this paper, we perform a comprehensive theoretical analysis of the phase competitions and excitations, on the basis of a microscopic interacting electron model taking into account the electron-phonon coupling, by paying special attention to the multi-stable properties. We follow the semiclassical analysis developed in Refs.…”

Section: Introductionmentioning

confidence: 99%

Phase Competition, Solitons, and Domain Walls in Neutral–Ionic Transition Systems

2016

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Phase competition and excitations in the one-dimensional neutral-ionic transition systems are theoretically studied comprehensively. From the semiclassical treatment of the bosonized Hamiltonian, we examine the competition among the neutral (N), ferroelectric-ionic (I ferro ) and paraelectric-ionic (Ipara) states. The phase transitions between them can become first-order when the fluctuation-induced higher-order commensurability potential is considered. In particular, the description of the first-order phase boundary between N and I ferro enables us to analyze N-I ferro domain walls. Soliton excitations in the three phases are described explicitly and their formation energies are evaluated across the phase boundaries. The characters of the soliton and domain-wall excitations are classified in terms of the topological charge and spin. The relevance to the experimental observations in the molecular neutral-ionic transition systems is discussed. We ascribe the pressure-induced crossover in tetrathiafulvalene-p-chloranil (TTF-CA) at a high-temperature region to that from the N to the Ipara state, and discuss its consequence.

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“…Recently, a paraelectric ionic phase with a uniform lattice has been found in the high pressure and high temperature region, 89,90 and it has been poposed that bond-length alternation is destroyed by thermal or quantum fluctuations of soliton pairs in the phase, where a soliton is a topological defect between I A and I B domains. [89][90][91][92] To investigate these mechanisms for polarization reversal, we need to establish an effective model where the THz-pulse induced dynamics can be calculated taking the effects of soliton pairs into account in large systems.…”

Section: Summary and Discussionmentioning

confidence: 99%

Terahertz pulse induced transitions between ionic and neutral phases and electronic polarization reversal in TTF-CA

2019

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We have investigated the terahertz (THz)-pulse induced dynamics of tetrathiafulvalene-pchloranil near the boundary between the ionic and neutral phases with the use of exact numerical calculations of an extended Hubbard model coupled with lattice motion. For the ionic phase, when the applied electric field of the THz-pulse opposes the electronic contribution to the electric polarization (electronic polarization)P el of the ground state and the maximum amplitude of electric field is greater than a threshold value, the THz-pulse excited state changes as I A → N → I B → N → I A → N → • • • (I A ground state case) or I B → N → I A → N → I B → N → • • • (I B ground state case), where N shows the neutral state, I A (I B) shows the ionic state withP el < 0 (P el > 0), and the phase of the bond length alternation of I A is opposite to that of I B. For the neutral phase, when the maximum amplitude of the electric field is greater than a threshold value, the THz-pulse excited state changes as N → I B → N → I A → N → I B → • • • (positive electric field case) or N → I A → N → I B → N → I A → • • • (negative electric field case). The phase transitions and electronic polarization reversal are driven by time variation of the lattice order parameter, which indicates the magnitude and phase of the bond length alternation, and the lattice motion is induced by THz-pulse excitation through the electron-lattice coupling. Transitions between the ionic and neutral phases occur and electronic polarization reverses on a picosecond time scale together with the realizable magnitude of the THz pulse both in the ionic and neutral phases near the phase boundary.

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Solitons in the Crossover between Band Insulator and Mott Insulator: Application to TTF-Chloranil under Pressure

Cited by 13 publications

References 13 publications

Topological charge transport by mobile dielectric-ferroelectric domain walls

Topological charge transport by mobile dielectric-ferroelectric domain walls

Phase Competition, Solitons, and Domain Walls in Neutral–Ionic Transition Systems

Terahertz pulse induced transitions between ionic and neutral phases and electronic polarization reversal in TTF-CA

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