Asymmetrical regulation of thermal transport in BAs/MoSSe van der Waals heterostructures with applied electric field

As a nondestructive regulation method, applying external electric field to regulate thermal transport has become one of the most effective reversible strategies. However, to date, using external electric fields to regulate thermal transport in van der Waals (vdW) heterostructures has been rarely reported, despite the great significance to engineering heat-transfer applications in electronics. Herein, based on the state-of-the-art first-principles calculations, we investigate the external electric field engineered thermal transport in BAs/MoSSe vdW twins heterostructures (i.e., BAs/MoSSe-I and BAs/MoSSe-II), which are constructed from monolayer BAs and Janus MoSSe. The thermal conductivity of different stacked BAs/MoSSe shows similar response to positive electric field. However, with negative electric field applied, the thermal conductivity of BAs/MoSSe-II is 22.4 times higher than that of BAs/MoSSe-I under the strength of $-0.2\mathrm{V}{\AA }^{-1}$. Detailed analysis reveals that the renormalization of phonons driven by the electric field mainly affects the phonon anharmonicity, which is induced by the electric field enhanced or weakened interlayer interaction, finally leading to the different response of the thermal conductivity for the two stacked BAs/MoSSe. The highly effective regulation of thermal transport in vdW heterostructures driven by the external electric fields as shown in this study is valuable for physical and engineering applications in electronics, thermoelectric, and thermal management.

Figure 1

The phonon spectrum along the high-symmetry path of $\mathrm{\Gamma }-M-K-\mathrm{\Gamma }$ and the partial density of states ($p\mathrm{DOS}$) of (a) BAs/MoSSe-I and (b) BAs/MoSSe-II under the representative external electric fields ($E_z=0$, $\pm 0.2\mathrm{V}{\AA }^{-1}$). (Inset: three views of the crystal structure; the large pale green, small bottle green, yellow, purple, and grass-green balls represent B, As, S, Mo, and Se atoms, respectively, and the external electric fields are marked by the yellow gradient arrow along the out of plane.)

Figure 2

The (a) distance of B and Se (S) atoms to S(Se) atoms, (b) dipole moment, and (c) band gap as the function of representative electric fields for BAs/MoSSe-I and BAs/MoSSe-II.

Figure 3

The major $p\mathrm{DOS}$ of As and Mo atoms under the external electric field of −0.2, 0, and $0.2\mathrm{V}{\AA }^{-1}$ for (a), (c) BAs/MoSSe-I and (b), (d) BAs/MoSSe-II.

Figure 4

The comparison between BAs/MoSSe-I and BAs/MoSSe-II of (a) thermal conductivity under representative electric fields, (b) frequency-dependent cumulative thermal conductivity at 300 K with ($\pm 0.2\mathrm{V}{\AA }^{-1}$) and without electric field, (c) the thermal conductivity contribution of different phonon branches as a function of electric fields, (d) the temperature-dependent thermal conductivity with ($\pm 0.2\mathrm{V}{\AA }^{-1}$) and without electric field, (e) normalized cumulative thermal conductivity with respect to the mean-free path (MFP), and (f) the size-dependent thermal conductivity considering boundary scattering.

Figure 5

Comparison of mode-level analysis of BAs/MoSSe-I and BAs/MoSSe-II under representative electric fields as a function of frequency for (a), (b) phonon relaxation time and (c), (d) Grüneisen parameter, respectively.

Figure 6

The difference in charge density under representative electric fields at $\pm 0.2\mathrm{V}{\AA }^{-1}$ $[\mathrm{\Delta }\rho =\rho \left(E_z\right)–\rho \left(E_z=0\right]$ and the average of the plane differential charge density along the out-of-plane direction at $\pm 0.2$, $\pm 0.4\mathrm{V}{\AA }^{-1}$ of (a)–(c) BAs/MoSSe-I, and (d)–(f) BAs/MoSSe-II. The isosurface is set as $1.2\times {10}^{-4}$, while yellow and blue refer to positive accumulation and negative depletion of charge, respectively. The charge transfer (g), (h) and −ICOHP (i), (j) as a function of electric field of BAs/MoSSe-I and BAs/MoSSe-II, while the value represents cumulative charge transfer of B and As atoms.