Electric-Field-Induced Insulator–Metal Transition in Ca<sub>2</sub>RuO<sub>4</sub>Probed by X-ray Absorption and Emission Spectroscopy

Sakaki, Mariko; Nakajima, N.; Nakamura, Fumihiko; Tezuka, Yasuhisa; Suzuki, Takashi

doi:10.7566/jpsj.82.093707

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…The corresponding optical micrograph shows that the sample is insulating (visibly bright) at zero voltage. This phase is labeled as the S phase to be consistent with the previously reported S-Pbca lattice structure of the insulating phase [33,34]. At slightly above 5 V, the current discontinuously jumps to a higher value.…”

Section: A Macroscopic Imagingsupporting

confidence: 87%

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

et al. 2019

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The Mott insulator Ca 2 RuO 4 is the subject of much recent attention following reports of emergent nonequilibrium steady states driven by applied electric fields or currents. In this paper, we carry out infrared nano-imaging and optical-microscopy measurements on bulk single crystal Ca 2 RuO 4 under conditions of steady current flow to obtain insight into the current-driven insulator-tometal transition. We observe macroscopic growth of the current-induced metallic phase, with nucleation regions for metal and insulator phases determined by the polarity of the current flow. A remarkable metal-insulator-metal microstripe pattern is observed at the phase front separating metal and insulator phases. The microstripes have orientations tied uniquely to the crystallographic axes, implying a strong coupling of the electronic transition to lattice degrees of freedom. Theoretical modeling further illustrates the importance of the current density and confirms a submicron-thick surface metallic layer at the phase front of the bulk metallic phase. Our work confirms that the electrically induced metallic phase is nonfilamentary and is not driven by Joule heating, revealing remarkable new characteristics of electrically induced insulator-metal transitions occurring in functional correlated oxides.

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Section: A Macroscopic Imagingsupporting

confidence: 87%

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

et al. 2019

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“…2(b), a selection of V − I characteristics as a func- tion of T obtained by I biasing the sample along the c axis is shown on a double logarithmic scale. Beyond the low J regime, when the samples show a clear insulating behavior, a negative differential resistance is observed 26,30 , in accordance with the dramatic reduction of resistivity observed in the ρ(T ) curves by increasing J. By further increasing the current, an ohmic dependence, signature of the IMT, is expected 15 .…”

Section: A Electrical Transport Measurementssupporting

confidence: 71%

Emergence of a metallic metastable phase induced by electrical current in Ca2RuO4

et al. 2019

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A comprehensive study of the behavior of the Mott insulator Ca2RuO4 under electrical current drive is performed by combining two experimental probes: the macroscopic electrical transport and the microscopic X-Ray diffraction. The resistivity, ρ, vs electric current density, J, and temperature, T , ρ(J,T), resistivity map is drawn. In particular, the meta-stable state, induced between the insulating and the metallic thermodynamic states by current biasing Ca2RuO4 single crystals, is investigated. Such an analysis, combined with the study of the resulting RuO6 octahedra energy levels, reveals that a metallic crystal phase emerges in the meta-stable regime. The peculiar properties of such a phase, coexisting with the well-established orthorhombic insulating and tetragonal metallic phases, allow to explain some of the unconventional and puzzling behaviors observed in the experiments, as a negative differential resistivity. arXiv:1912.01690v1 [cond-mat.str-el]

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“…This occurs because a higher power is dissipated in the sample due to its increased resistance. The drop of more than one order of magnitude in j all-met indicates large and irreversible changes in the sample properties, consistent with the previous observation of crack formation at similar current values [40].…”

Section: Current-driven Mit In the Presence Of Cracks And Defectssupporting

confidence: 91%

Role of local temperature in the current-driven metal-insulator transition of Ca2RuO4

Mattoni,

Yonezawa,

Nakamura

et al. 2020

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It was recently reported that a continuous electric current is a powerful control parameter to trigger changes in the electronic structure and metal-insulator transitions (MITs) in Ca 2 RuO 4 . However, the spatial evolution of the MIT and the implications of the unavoidable Joule heating have not been clarified yet, often hindered by the difficulty to asses the local sample temperature. In this work, we perform infrared thermal imaging on single-crystal Ca 2 RuO 4 while controlling the MIT by electric current. The change in emissivity at the phase transition allows us to monitor the gradual formation and expansion of metallic phase upon increasing current. Our local temperature measurements indicate that, within our experimental resolution, the MIT always occurs at the same local transition temperatures, irrespectively if driven by temperature or by current. Our results highlight the importance of local heating, phase coexistence, and microscale inhomogeneity when studying strongly correlated materials under the flow of electric current.

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Electric-Field-Induced Insulator–Metal Transition in Ca₂RuO₄Probed by X-ray Absorption and Emission Spectroscopy

Cited by 9 publications

References 19 publications

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

Emergence of a metallic metastable phase induced by electrical current in Ca2RuO4

Role of local temperature in the current-driven metal-insulator transition of Ca2RuO4

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Electric-Field-Induced Insulator–Metal Transition in Ca2RuO4Probed by X-ray Absorption and Emission Spectroscopy

Cited by 9 publications

References 19 publications

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

Nano-Resolved Current-Induced Insulator-Metal Transition in the Mott Insulator Ca2RuO4

Emergence of a metallic metastable phase induced by electrical current in Ca2RuO4

Role of local temperature in the current-driven metal-insulator transition of Ca2RuO4

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Electric-Field-Induced Insulator–Metal Transition in Ca₂RuO₄Probed by X-ray Absorption and Emission Spectroscopy