Ultrafast Electric Field Pulse Control of Giant Temperature Change in Ferroelectrics

Y. Qi, S. Liu, A. M. Lindenberg, and A. M. Rappe

Phys. Rev. Lett. 120, 055901 – Published 30 January 2018

Abstract

There is a surge of interest in developing environmentally friendly solid-state-based cooling technology. Here, we point out that a fast cooling rate ( $\approx 10^{11} K / s$ ) can be achieved by driving solid crystals to a high-temperature phase with a properly designed electric field pulse. Specifically, we predict that an ultrafast electric field pulse can cause a giant temperature decrease up to 32 K in ${PbTiO}_{3}$ occurring on few picosecond time scales. We explain the underlying physics of this giant electric field pulse-induced temperature change with the concept of internal energy redistribution: the electric field does work on a ferroelectric crystal and redistributes its internal energy, and the way the kinetic energy is redistributed determines the temperature change and strongly depends on the electric field temporal profile. This concept is supported by our all-atom molecular dynamics simulations of ${PbTiO}_{3}$ and ${BaTiO}_{3}$ . Moreover, this internal energy redistribution concept can also be applied to understand electrocaloric effect. We further propose new strategies for inducing giant cooling effect with ultrafast electric field pulse. This Letter offers a general framework to understand electric-field-induced temperature change and highlights the opportunities of electric field engineering for controlled design of fast and efficient cooling technology.

Received 24 October 2016

DOI:https://doi.org/10.1103/PhysRevLett.120.055901

Physics Subject Headings (PhySH)

Electrocaloric effect

Ferroelectrics

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Y. Qi¹, S. Liu², A. M. Lindenberg^3,4, and A. M. Rappe¹

¹Department of Chemistry, The Makineni Theoretical Laboratories, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, USA
²Geophysical Laboratory, Carnegie Institution for Science, Washington, D.C. 20015, USA
³Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA
⁴SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

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Vol. 120, Iss. 5 — 2 February 2018

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Images

Figure 1
Negative EPITC associated with the rhombohedral to orthorhombic phase transition in ${BaTiO}_{3}$ . (a) Electric field, potential energy, temperature, and polarization vs time. The potential energy of the ground structure at $T = 0 K$ is set as the zero point potential energy. An $80 kV / cm$ electric field is applied along the (110) direction with $T = 101 K$ . The electric field rises to its steady-state value within 5 ps, rather than instantaneously. This is chosen because, for the negative EPITC, less work ( $W$ ) and entropy production are preferred. In our MD simulations, the rhombohedral to orthorhombic phase transition occurs at 102 K under zero electric field and at 94 K under an $80 kV / cm$ electric field. Therefore, at 101 K, ${BaTiO}_{3}$ is at its rhombohedral phase under zero electric field and an $80 kV / cm$ electric field is large enough for triggering a rhombohedral to orthorhombic phase transition. (b) Schematic plot of potential energy vs temperature for the two phases, demonstrating the electric-field-induced phase transition and ultrafast temperature reduction. The solid blue and green lines indicate the potential energies of equilibrated states at different temperatures. The blue and green circles represent the states before and after the application of electric field.
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Figure 2
Time evolution of the electric field pulse, potential energy, temperature, and polarization along the three Cartesian axes for (a) $BaTi O_{3}$ , under a single-cycle terahertz electric field pulse perpendicular to the polarization in tetragonal ${BaTiO}_{3}$ . The tetragonal to cubic phase transition of ${BaTiO}_{3}$ under zero electric field occurs at 160 K in our MD simulation [18]. This pulse induces a tetragonal to cubic phase transition, which was demonstrated by both the potential energy and polarization profile. For the middle plot, the blue line indicates the temperature evolution under zero electric field pulse, as a comparison. (b) $PbTi O_{3}$ , under a half-cycle terahertz electric field pulse antiparallel to polarization in ${PbTiO}_{3}$ . The tetragonal to cubic phase transition of ${PbTiO}_{3}$ under zero electric field occurs at 395 K in our MD simulation [22]. For ${PbTiO}_{3}$ , the negative EPITC is giant (32 K), due to the large transition energy. For ${BaTiO}_{3}$ and ${PbTiO}_{3}$ , we used electric field pulses with different profiles; actually, either of them works well in scrambling the local polarization, and they are similar in effectiveness. If we use a pulse with a full cycle, it should be perpendicular to the polar axis. This pulse will reorient the polarization first and then flip parts of local polarization in this newly oriented polar direction. If a half-cycle pulse is selected, it should be antiparallel to the polar direction in order to reverse parts of local polarization and drive the crystal to a nonpolar state.
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Figure 3
Time evolution of the electric field pulse, potential energy, temperature, and lattice constants for ${BaTiO}_{3}$ and ${PbTiO}_{3}$ under the application of a $600 kV / cm$ electric field. (a) Electric field is applied and the ${BaTiO}_{3}$ crystal undergoes a cubic to tetragonal phase transition, with a 9 K temperature increase. (b) Electric field is applied on a ${PbTiO}_{3}$ crystal, causing a phase transition with a 50 K temperature increase.
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Figure 4
Schematic representation of the polarization evolution in the Gibbs free energy profile. The outer two minima represent the states with positive and negative polarization. The central minimum represents a cubic phase. The solid blue curve represents that the electric field pulse drives the ferroelectric crystal from its tetragonal phase toward the cubic and over the energy barrier. The dashed blue curve indicates that the system evolves to the cubic phase after the pulse. For ${PbTiO}_{3}$ , because the energy barrier in the Gibbs free energy profile, which relates to the energy required for polar nuclei formation and growth, is high at $T \approx T_{C}$ , polar nuclei are slow to form and the system can be trapped in the cubic local minimum for nanoseconds, which is long enough for heat transfer. For ${BaTiO}_{3}$ , the energy barrier between polar and nonpolar states is much lower. As a result, the supercooled nonpolar state can last for approximately 100 ps.
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