Comparison between $s$- and $d$-electron mediated transport in a photoswitching dithienylethene molecule using ab initio transport methods

The influence of the electrode’s Fermi surface on the transport properties of a photoswitching molecule is investigated with state-of-the-art ab initio transport methods. We report results for the conducting properties of the two forms of dithienylethene attached either to Ag or to nonmagnetic Ni leads. The $I$-$V$ curves of the Ag/dithienylethene/Ag device are found to be very similar to those reported previously for Au. In contrast, when Ni is used as the electrode material the zero-bias transmission coefficient is profoundly different as a result of the role played by the Ni $d$ bands in the bonding between the molecule and the electrodes. Intriguingly, despite these differences the overall conducting properties depend little on the electrode material. We thus conclude that electron transport in dithienylethene is, for the cases studied, mainly governed by the intrinsic electronic structure of the molecule.

Figure 1

The two geometrical configurations of the DTE molecule investigated in this work. The closed form of the molecule is shown in the top panel and the open form in the one below. Color code: light gray small balls (light blue) H; dark gray (red) C; light gray large balls (light gray) S.

Figure 2

Geometry of the closed form of the molecule inserted between two Ag leads.

Figure 3

Lead’s surface DOS projected over $s$ and $d$ orbitals of Au, Ag, and Ni.

Figure 4

Density of states for the two conformations of the DTE molecule in vacuum.

Figure 5

Self-consistent $I$-$V$ characteristics for the closed and open molecules sandwiched between two Ag electrodes. Also shown in the inset is the ratio between the current for the closed and the open molecule with the large anchoring distance.

Figure 6

Non-self-consistent $I$-$V$ characteristics for the closed and open molecules sandwiched between two Ag electrodes. This is obtained by integrating the zero-bias transmission function over the bias window. The inset shows the ratio between the calculated current for the closed and open molecules.

Figure 7

Transmission coefficient as a function of energy for the closed molecule at different bias voltages. The vertical lines denotes the bias window.

Figure 8

Transmission coefficient as a function of energy for the open molecule at different bias voltages. The vertical lines denote the bias window.

Figure 9

Projected density of states for four C atoms of the closed isomer at different applied bias. The atom labels C${}_1$, C${}_2$, C${}_3$ and C${}_4$ are defined in figure 1.

Figure 10

Projected density of states for four C atoms of the open isomer at different applied bias. The atom labels C${}_1$, C${}_2$, C${}_3$, and C${}_4$ are defined in Fig. 1.

Figure 11

Self-consistent $I$-$V$ characteristics for the closed and open molecules sandwiched between two Ni electrodes. The inset shows the ratio between the calculated current for the closed and open molecule.

Figure 12

Non-self-consistent $I$-$V$ characteristics for the closed and open molecules sandwiched between two Ni electrodes. This is obtained by integrating the zero-bias transmission function over the bias window. The inset shows the ratio between the calculated current for the closed and open molecule.

Figure 13

Transmission coefficient as a function of energy for the closed molecule sandwiched between two Ni electrodes at different voltages. The vertical lines denote the bias window.

Figure 14

Transmission coefficient as a function of energy for the open molecule sandwiched between two Ni electrodes at different voltages. The vertical lines denotes the bias window.

Figure 15

Projected density of states for four C atoms of the closed isomer at different applied bias. The atom labels S${}_1$, S${}_2$, C${}_1$, C${}_2$, C${}_3$, and C${}_4$ are defined in Fig. 1. The vertical lines define the bias window.

Figure 16

Projected density of states for four C atoms of the open isomer at different applied bias. The atom labels S${}_1$, S${}_2$, C${}_1$, C${}_2$, C${}_3$, and C${}_4$ are defined in Fig. 1. The vertical lines define the bias window.

Figure 17

PDOS for one Ag lead surface atom and the S${}_1$ atom at $V=0$ V. The atom label S${}_1$ is defined in Fig. 1.

Figure 18

PDOS for one Ni lead surface atom and the S${}_1$ atom at $V=0$ V. The PDOS for the Ni 3$d$ states have been scaled by a factor $0.1$ for visibility. The atom label S${}_1$ is defined in Fig. 1.