Early-Stage Dynamics of Light-Matter Interaction Leading to the Insulator-to-Metal Transition in a Charge Ordered Organic Crystal

Kawakami, Y.; Fukatsu, Takeshi; Sakurai, Yasuki; Unno, H.; Itoh, Hirotake; Iwai, Shinichiro; Sasaki, T.; Yamamoto, Kaoru; Yakushi, Kyuya; Yonemitsu, Kenji

doi:10.1103/physrevlett.105.246402

Cited by 81 publications

(80 citation statements)

References 19 publications

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“…4b shows a dip at B0.15 eV (which equals the vibration peak of the optical conductivity at 140 K (refs 29,30) in the inset) reflecting the destructive interference between charge motion and vibration 33 . Therefore, the intense 20 fs oscillation detected before the appearance of the charge-vibration interference dip is attributed to the oscillation of the CO gap.…”

Section: Resultsmentioning

confidence: 99%

Optical freezing of charge motion in an organic conductor

et al. 2014

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Dynamical localization, that is, reduction of the intersite electronic transfer integral t by an alternating electric field, E(o), is a promising strategy for controlling strongly correlated systems with a competing energy balance between t and the Coulomb repulsion energy. Here we describe a charge localization induced by the 9.3 MVcm À 1 instantaneous electric field of a 1.5 cycle (7 fs) infrared pulse in an organic conductor a-(bis[ethylenedithio]-tetrathiafulvalene) 2 I 3 . A large reflectivity change of 425% and a coherent charge oscillation along the time axis reflect the opening of the charge ordering gap in the metallic phase. This optical freezing of charges, which is the reverse of the photoinduced melting of electronic orders, is attributed to the B10% reduction of t driven by the strong, high-frequency (oZt/:) electric field.

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Section: Resultsmentioning

confidence: 99%

Optical freezing of charge motion in an organic conductor

et al. 2014

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“…Recent results of the pump-probe experiment using three-optical cycle (12 fs) IR pulses shows that the initial process occurs in the timescale of ca. 15 fs [38], as shown in Section 3.5. Such an ultrafast response indicates that the molecular rearrangement or structural change is unimportant and that electronic processes play a main role because the initial response is as fast as the timescale of the intermolecular CT (ca.…”

Section: Photoinduced Melting Of Co and Metallic Domain Formation Inmentioning

confidence: 93%

“…[37], high-time resolution spectroscopy using infrared 3-optical cycle (12 fs) pulses (3.5.) [38]. The PIMT in the Dimer-Mott insulator κ-(d-ET) 2 Cu[N(CN) 2 ]Br is discussed in Section 4 [39].…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering

Iwai¹

2012

Crystals

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Photoinduced phase transitions in organic compounds with strong electron correlation ET [bis(ethylenedithio)-tetrathiafulvalene)-based salts α-(ET) 2 I 3 , θ-(ET) 2 RbZn(SCN) 4 , κ-(d-ET) 2 Cu[N(CN) 2 Br] were discussed based, on time resolved optical pump-probe spectroscopy using ~150 fs mid-infrared pulse, 12 fs near infrared pulse, and sub-picosecond terahertz pulse. (i) In charge-ordered insulators α-(ET) 2 I 3 and θ-(ET) 2 RbZn(SCN) 4 , we captured ultrafast snapshots of charge dynamics i.e., immediate (ca. 15 fs) generation of a microscopic metallic state (or equivalently the microscopic melting of the charge order) which is driven by the coherent oscillation (period; 18 fs) of correlated electrons. Subsequently, condensation of the microscopic metallic state to the macroscopic scale occurs in α-(ET) 2 I 3 . However, in θ-(ET) 2 RbZn(SCN) 4 , such condensation is prevented by the large potential barrier reflecting the structural difference between the insulator and metal; (ii) In a Dimer-Mott insulator κ-(d-ET) 2 Cu[N(CN) 2 Br], photogeneration of the metallic state rises during ca. 1 ps that is much slower than the melting of charge order, because the photoinduced insulator to metal transition is driven by the intradimer molecular displacement in the dimer Mott insulator. The ultrafast dynamics of photoinduced insulator-metal transitions depend strongly on the molecular arrangement, reflecting various competing phases in the ET sheets.

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“…The recovery of the second harmonics corresponds to this slow decay. Recently, Kawakami et al, uncovered the early dynamic process of the photoinduced phase transition using a 12 fs laser [140].…”

Section: α-(Bedt-ttf) 2 I 3 and Related Compoundsmentioning

confidence: 99%

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

Yakushi

2012

Crystals

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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

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Early-Stage Dynamics of Light-Matter Interaction Leading to the Insulator-to-Metal Transition in a Charge Ordered Organic Crystal

Cited by 81 publications

References 19 publications

Optical freezing of charge motion in an organic conductor

Optical freezing of charge motion in an organic conductor

Photoinduced Phase Transitions in α-, θ-, and κ-type ET Salts: Ultrafast Melting of the Electronic Ordering

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

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