A phononic switch based on ferroelectric domain walls

The ease with which domain walls (DWs) in ferroelectric materials can be written and erased provides a versatile way to dynamically modulate heat fluxes. In this Rapid Communication we evaluate the thermal boundary resistance (TBR) of ${180}^{\circ }$ DWs in the prototype ferroelectric perovskite ${\mathrm{PbTiO}}_3$ within the numerical formalisms of nonequilibrium molecular dynamics and nonequilibrium Green's functions. An excellent agreement is obtained for the TBR of an isolated DW derived from both approaches, which reveals the harmonic character of the phonon-DW scattering mechanism. The thermal resistance of the ferroelectric material is shown to increase up to around 20%, in the system sizes considered here, due to the presence of a single DW, and larger resistances can be attained by the incorporation of more DWs along the path of thermal flux. These results, obtained at device operation temperatures, prove the viability of an electrically actuated phononic switch based on ferroelectric DWs.

Figure 1

Schematic view of the supercell for a simulation in which thermal transport through two independent DWs is evaluated. The red and blue rectangles illustrate the position of the thermal source and sink, respectively, and the transport directions are indicated with horizontal arrows.

Figure 2

Temperature (top) and polarization (bottom) profiles along the transport direction $z$ for the case of a monodomain ${\mathrm{PbTiO}}_3$. Heat flows from the heat source at $z=0$ to the heat sink at $z=35$ nm. Data in red are used to fit the thermal gradient. The uniform ferroelectric distortion is sketched in the inset of the bottom panel.

Figure 3

Temperature (top) and polarization (bottom) profiles along the transport direction $z$ for the case with one DW. Heat source and sink are placed as in Fig. 2 and the DWs are at $\sim 17$ and $\sim 52$ nm. The inset of the top panel shows a zoomed view of the temperature profile at one of the DW; the relevant temperatures used to calculate the TBR are indicated.

Figure 4

Top: TBR as a function of temperature computed within the harmonic NEGF approach as $G_{\text{DW}}^{-1}-G_{\text{mono}}^{-1}$, where $G_{\text{DW}}$ ($G_{\text{mono}}$) is the thermal conductance of the case with (without) DW. Bottom: Phonon transmission as a function of frequency for the case of a monodomain (continuous line) and a DW (dashed line).

Figure 5

Temperature and polarization profiles along the transport direction $z$ for the cases with two DWs separated by (a), (b) $\sim 1.5$ nm and (c), (d) $\sim 4$ nm.