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Electric control of topological phase transitions in Dirac semimetal thin films.

Pan H, Wu M, Liu Y, Yang SA - Sci Rep (2015)

Bottom Line: We show that through the interplay between the quantum confinement effect and the field-induced coupling between sub-bands, the sub-band gap can be tuned and inverted.During this process, the system undergoes a topological phase transition between a trivial band insulator and a quantum spin Hall insulator.Consequently, one can switch the topological edge channels on and off by purely electrical means, making the system a promising platform for constructing topological field effect transistors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Beihang University, Beijing 100191, China.

ABSTRACT
Dirac semimetals host three-dimensional (3D) Dirac fermion states in the bulk of crystalline solids, which can be viewed as 3D analogs of graphene. Owing to their relativistic spectrum and unique topological character, these materials hold great promise for fundamental-physics exploration and practical applications. Particularly, they are expected to be ideal parent compounds for engineering various other topological states of matter. In this report, we investigate the possibility to induce and control the topological quantum spin Hall phase in a Dirac semimetal thin film by using a vertical electric field. We show that through the interplay between the quantum confinement effect and the field-induced coupling between sub-bands, the sub-band gap can be tuned and inverted. During this process, the system undergoes a topological phase transition between a trivial band insulator and a quantum spin Hall insulator. Consequently, one can switch the topological edge channels on and off by purely electrical means, making the system a promising platform for constructing topological field effect transistors.

No MeSH data available.


Calculated LDOS of a side surface for Cd3As2 thin film.(a) is for point A (trivial insulator) and (b) is for point C (QSH insulator) as marked in Fig. 4(a). The calculation is for a slab which is semi-infinite along y-direction and the parameters are the same as for Fig. 4.
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f5: Calculated LDOS of a side surface for Cd3As2 thin film.(a) is for point A (trivial insulator) and (b) is for point C (QSH insulator) as marked in Fig. 4(a). The calculation is for a slab which is semi-infinite along y-direction and the parameters are the same as for Fig. 4.

Mentions: Similar analysis applies to Cd3As2 as well. In Fig. 3, we plot the variation of its confinement-induced gap versus the film thickness, which clearly shows the oscillation behavior of the gap31. One observes that the critical thickness is at about 37 layers. Here we choose a film thickness of layers (L = 50.86 nm) for demonstration. The variations of the gap with respect to the E field as well as representative energy spectra are shown in Fig. 4. Again the gap closing and reopening process similar to Fig. 1(a) is observed. The critical value of  mV/nm also agrees well with the estimation  mV/nm from Eq.(13). The energy spectra also coincide with our previous analysis. Figure 5 shows the side surface LDOS plots for states A and C (marked in Fig. 4(a), clearly showing the appearance of topological edge states across the transition. These results show qualitatively the same features as those for Na3Bi.


Electric control of topological phase transitions in Dirac semimetal thin films.

Pan H, Wu M, Liu Y, Yang SA - Sci Rep (2015)

Calculated LDOS of a side surface for Cd3As2 thin film.(a) is for point A (trivial insulator) and (b) is for point C (QSH insulator) as marked in Fig. 4(a). The calculation is for a slab which is semi-infinite along y-direction and the parameters are the same as for Fig. 4.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588596&req=5

f5: Calculated LDOS of a side surface for Cd3As2 thin film.(a) is for point A (trivial insulator) and (b) is for point C (QSH insulator) as marked in Fig. 4(a). The calculation is for a slab which is semi-infinite along y-direction and the parameters are the same as for Fig. 4.
Mentions: Similar analysis applies to Cd3As2 as well. In Fig. 3, we plot the variation of its confinement-induced gap versus the film thickness, which clearly shows the oscillation behavior of the gap31. One observes that the critical thickness is at about 37 layers. Here we choose a film thickness of layers (L = 50.86 nm) for demonstration. The variations of the gap with respect to the E field as well as representative energy spectra are shown in Fig. 4. Again the gap closing and reopening process similar to Fig. 1(a) is observed. The critical value of  mV/nm also agrees well with the estimation  mV/nm from Eq.(13). The energy spectra also coincide with our previous analysis. Figure 5 shows the side surface LDOS plots for states A and C (marked in Fig. 4(a), clearly showing the appearance of topological edge states across the transition. These results show qualitatively the same features as those for Na3Bi.

Bottom Line: We show that through the interplay between the quantum confinement effect and the field-induced coupling between sub-bands, the sub-band gap can be tuned and inverted.During this process, the system undergoes a topological phase transition between a trivial band insulator and a quantum spin Hall insulator.Consequently, one can switch the topological edge channels on and off by purely electrical means, making the system a promising platform for constructing topological field effect transistors.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Beihang University, Beijing 100191, China.

ABSTRACT
Dirac semimetals host three-dimensional (3D) Dirac fermion states in the bulk of crystalline solids, which can be viewed as 3D analogs of graphene. Owing to their relativistic spectrum and unique topological character, these materials hold great promise for fundamental-physics exploration and practical applications. Particularly, they are expected to be ideal parent compounds for engineering various other topological states of matter. In this report, we investigate the possibility to induce and control the topological quantum spin Hall phase in a Dirac semimetal thin film by using a vertical electric field. We show that through the interplay between the quantum confinement effect and the field-induced coupling between sub-bands, the sub-band gap can be tuned and inverted. During this process, the system undergoes a topological phase transition between a trivial band insulator and a quantum spin Hall insulator. Consequently, one can switch the topological edge channels on and off by purely electrical means, making the system a promising platform for constructing topological field effect transistors.

No MeSH data available.