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Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4.

Nakamura F, Sakaki M, Yamanaka Y, Tamaru S, Suzuki T, Maeno Y - Sci Rep (2013)

Bottom Line: The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy.Moreover, the switching is accompanied by a bulk structural transition.Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.

View Article: PubMed Central - PubMed

Affiliation: ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan.

ABSTRACT
Recently, "application of electric field (E-field)" has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.

No MeSH data available.


Switching in voltage-current curves for Ca2RuO4.(a) The voltage-current curves obtained by a two terminal method with continuous E∥c at 295 K. There exists a large hysteresis during the voltage sweeps. (b) The switching curves for pulse application E⊥c with a different duration time. The threshold Vth and Ith are defined from the maximum voltage in the IV curve. (c) Total heating Qth at the switching threshold estimated by Qth = ∫Vth(t) Ith(t) dt in an adiabatic model plotted as a function of duration time. The almost linear increase of Qth with duration time gives clear evidence that the switching is not dominated by heating. The solid line is guide for the eye. (d) Eth below 320 K plotted as a function of T. The solid line is a fit with Eth(T)/E0 = exp(−T/T0), using the characteristic values E0  = 80 kV/cm and T0  = 39.2 K. (e, f, g) The voltage-current curves measured by using a four-probe method for a step-shaped sample consisting of different cross-sectional areas, as shown in the inset. The current is plotted against (e) voltage and (f) E-field. (g) The current density plotted as a function of E-field, showing that all the switching curves agree with each other.
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f1: Switching in voltage-current curves for Ca2RuO4.(a) The voltage-current curves obtained by a two terminal method with continuous E∥c at 295 K. There exists a large hysteresis during the voltage sweeps. (b) The switching curves for pulse application E⊥c with a different duration time. The threshold Vth and Ith are defined from the maximum voltage in the IV curve. (c) Total heating Qth at the switching threshold estimated by Qth = ∫Vth(t) Ith(t) dt in an adiabatic model plotted as a function of duration time. The almost linear increase of Qth with duration time gives clear evidence that the switching is not dominated by heating. The solid line is guide for the eye. (d) Eth below 320 K plotted as a function of T. The solid line is a fit with Eth(T)/E0 = exp(−T/T0), using the characteristic values E0 = 80 kV/cm and T0 = 39.2 K. (e, f, g) The voltage-current curves measured by using a four-probe method for a step-shaped sample consisting of different cross-sectional areas, as shown in the inset. The current is plotted against (e) voltage and (f) E-field. (g) The current density plotted as a function of E-field, showing that all the switching curves agree with each other.

Mentions: To investigate the switching phenomena, voltage-current (V-I) curves have been measured by using a two-probe method for CRO single crystals. Let us first present the results of V-biased experiments. Figure 1 (a) shows changes in I at 295 K as a function of V. With increasing V along the c axis, I first rises linearly at a rate indicating nonmetallic conduction of ~60 Ωcm, but then jumps discontinuously from 18 to 700 mA at 0.8 V, indicating switching, and is followed by an increase at a rate indicating metallic conduction of ~0.4 Ωcm. Surprisingly, the threshold value Eth ~ 40 V/cm for E//c is far smaller than our expectation of ~4 MV/cm. We typically obtained Eth ~ 50 V/cm for E⊥c. Thus, the value of the Eth is almost independent of the E-field direction.


Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4.

Nakamura F, Sakaki M, Yamanaka Y, Tamaru S, Suzuki T, Maeno Y - Sci Rep (2013)

Switching in voltage-current curves for Ca2RuO4.(a) The voltage-current curves obtained by a two terminal method with continuous E∥c at 295 K. There exists a large hysteresis during the voltage sweeps. (b) The switching curves for pulse application E⊥c with a different duration time. The threshold Vth and Ith are defined from the maximum voltage in the IV curve. (c) Total heating Qth at the switching threshold estimated by Qth = ∫Vth(t) Ith(t) dt in an adiabatic model plotted as a function of duration time. The almost linear increase of Qth with duration time gives clear evidence that the switching is not dominated by heating. The solid line is guide for the eye. (d) Eth below 320 K plotted as a function of T. The solid line is a fit with Eth(T)/E0 = exp(−T/T0), using the characteristic values E0  = 80 kV/cm and T0  = 39.2 K. (e, f, g) The voltage-current curves measured by using a four-probe method for a step-shaped sample consisting of different cross-sectional areas, as shown in the inset. The current is plotted against (e) voltage and (f) E-field. (g) The current density plotted as a function of E-field, showing that all the switching curves agree with each other.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC3756342&req=5

f1: Switching in voltage-current curves for Ca2RuO4.(a) The voltage-current curves obtained by a two terminal method with continuous E∥c at 295 K. There exists a large hysteresis during the voltage sweeps. (b) The switching curves for pulse application E⊥c with a different duration time. The threshold Vth and Ith are defined from the maximum voltage in the IV curve. (c) Total heating Qth at the switching threshold estimated by Qth = ∫Vth(t) Ith(t) dt in an adiabatic model plotted as a function of duration time. The almost linear increase of Qth with duration time gives clear evidence that the switching is not dominated by heating. The solid line is guide for the eye. (d) Eth below 320 K plotted as a function of T. The solid line is a fit with Eth(T)/E0 = exp(−T/T0), using the characteristic values E0 = 80 kV/cm and T0 = 39.2 K. (e, f, g) The voltage-current curves measured by using a four-probe method for a step-shaped sample consisting of different cross-sectional areas, as shown in the inset. The current is plotted against (e) voltage and (f) E-field. (g) The current density plotted as a function of E-field, showing that all the switching curves agree with each other.
Mentions: To investigate the switching phenomena, voltage-current (V-I) curves have been measured by using a two-probe method for CRO single crystals. Let us first present the results of V-biased experiments. Figure 1 (a) shows changes in I at 295 K as a function of V. With increasing V along the c axis, I first rises linearly at a rate indicating nonmetallic conduction of ~60 Ωcm, but then jumps discontinuously from 18 to 700 mA at 0.8 V, indicating switching, and is followed by an increase at a rate indicating metallic conduction of ~0.4 Ωcm. Surprisingly, the threshold value Eth ~ 40 V/cm for E//c is far smaller than our expectation of ~4 MV/cm. We typically obtained Eth ~ 50 V/cm for E⊥c. Thus, the value of the Eth is almost independent of the E-field direction.

Bottom Line: The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy.Moreover, the switching is accompanied by a bulk structural transition.Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.

View Article: PubMed Central - PubMed

Affiliation: ADSM, Hiroshima University, Higashi-Hiroshima 739-8530, Japan.

ABSTRACT
Recently, "application of electric field (E-field)" has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ~40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.

No MeSH data available.