We investigate theoretically the quantum transport properties of a twisted bilayer copper phthalocyanine (CuPc) molecular device, in which the bottom-layer CuPc molecule is connected to V-shaped zigzag-edged graphene nanoribbon electrodes. Based on a non-equilibrium Green's function approach in combination with density-functional theory, we find that the twist angle effectively modulates the electron interaction between the bilayer CuPc molecules. HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital) gap, spin filtering efficiency (SFE) and spin-dependent conductance of the bilayer CuPc molecular device could be modulated by changing the twist angle. The conductance reaches its maximum when the twist angle is 0° while the largest SFE is achieved when = 60°. The twist angle-induced exotic transport phenomena can be well explained by analyzing the transmission spectra, molecular energy level spectra and scattering states of the twisted bilayer CuPc molecular device. The tunable conductance, HOMO-LUMO gap and spin filtering twist angle are helpful for predicting how a two-molecule system may behave with twist angle.
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http://dx.doi.org/10.1039/d0na01079k | DOI Listing |
Phys Rev Lett
December 2024
Donostia International Physics Center, Paseo Manuel de Lardizabal 4, 20018 Donostia-San Sebastian, Spain.
The chiral lattice structure of twisted bilayer graphene with D_{6} symmetry allows for intrinsic photogalvanic effects only at off-normal incidence, while additional extrinsic effects are known to be induced by a substrate or a gate potential. In this Letter, we first compute the intrinsic effects and show they reverse sign at the magic angle, revealing a band inversion at the Γ point. We next consider different extrinsic effects, showing how they can be used to track the strengths of the substrate coupling or electric displacement field.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Department of Physics, Stanford University, Stanford, California 94305, USA.
Inspired by the observation of increasingly one-dimensional (1D) behavior with decreasing temperature in small-angle twisted bilayers of WTe_{2} (tWTe_{2}), we theoretically explore the exotic sliding regimes that could be realized in tWTe_{2}. At zero displacement field, while hole-doped tWTe_{2} can be thought of as an array of weakly coupled conventional two-flavor 1D electron gases (1DEGs), the electron-doped regime is equivalent to coupled four-flavor 1DEGs, due to the presence of an additional "valley" degree of freedom. In the decoupled limit, the electron-doped system can thus realize phases with a range of interesting ordering tendencies, including 4k_{F} charge-density-wave and charge-4e superconductivity.
View Article and Find Full Text PDFNano Lett
January 2025
Department of Physics and Astronomy, University of Wyoming, Laramie, Wyoming 82071, United States.
Anisotropic materials with low symmetries hold significant promise for next-generation electronic and quantum devices. 2M-WS, which is a candidate for topological superconductivity, has garnered considerable interest. However, a comprehensive understanding of how its anisotropic features contribute to unconventional superconductivity, along with a simple, reliable method to identify its crystal orientation, remains elusive.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Physics and Chemistry, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, Republic of Korea.
Magnetotransport of conventional semiconductor based double layer systems with barrier suppressed interlayer tunneling has been a rewarding subject due to the emergence of an interlayer coherent state that behaves as an excitonic superfluid. Large angle twisted bilayer graphene offers unprecedented strong interlayer Coulomb interaction, since both layer thickness and layer spacing are of atomic scale and a barrier is no more needed as the twist induced momentum mismatch suppresses tunneling. The extra valley degree of freedom also adds richness.
View Article and Find Full Text PDFNat Commun
January 2025
Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA.
Applying long wavelength periodic potentials on quantum materials has recently been demonstrated to be a promising pathway for engineering novel quantum phases of matter. Here, we utilize twisted bilayer boron nitride (BN) as a moiré substrate for band structure engineering. Small-angle-twisted bilayer BN is endowed with periodically arranged up and down polar domains, which imprints a periodic electrostatic potential on a target two-dimensional (2D) material placed on top.
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