Spin-Conserving Resonant Tunneling in Twist-Controlled WSe₂-hBN-WSe₂ Heterostructures

Abstract

We investigate interlayer tunneling in heterostructures consisting of two tungsten diselenide (WSe) monolayers with controlled rotational alignment, and separated by hexagonal boron nitride. In samples where the two WSe monolayers are rotationally aligned we observe resonant tunneling, manifested by a large conductance and negative differential resistance in the vicinity of zero interlayer bias, which stem from energy- and momentum-conserving tunneling. Because the spin-orbit coupling leads to coupled spin-valley degrees of freedom, the twist between the two WSe monolayers allows us to probe the conservation of spin-valley degree of freedom in tunneling. In heterostructures where the two WSe monolayers have a 180° relative twist, such that the Brillouin zone of one layer is aligned with the time-reversed Brillouin zone of the opposite layer, the resonant tunneling between the layers is suppressed. These findings provide evidence that, in addition to momentum, the spin-valley degree of freedom is also conserved in vertical transport.

Tunneling spectroscopy of localized states of WS2 barriers in vertical van der Waals heterostructures

“…Tunneling spectroscopy in van der Waals and other heterostructures is a powerful tool that can reveal unique information about the density of states (DOS) of the electrodes [1,2], about phonons (or other excitations) [3][4][5], about the chiral, valley [6] and spin states of the carriers [7,8] and their interactions [9]. Recently it was shown that the presence of defects in crystalline hexagonal boron nitride (h-BN) tunneling barriers can be detected in the tunneling spectra, which is dominated by Coulomb blockade effects [10,11].…”

Fermi Velocity Modulation Induced Low‐Bias Negative Differential Resistance in Graphene Double Barrier Resonant Tunneling diode

“…Numerous types of 2D materials have been implemented to fabricate high‐performance NDR devices. The critical performance metrics of PVR and NDR V at room temperature are compared with the state of the art of fabricated 2Ds‐based NDR devices including graphene [ 49,52,69–75 ] and other 2Ds [ 76–82 ] as well as commercialized RTDs [ 81,83,84 ] as illustrated in Figure 6 . Graphene‐channel‐based (graphene [Gr], [ 43,69 ] graphene nanoribbon [GNR], [ 67,71 ] fluorinated graphene [FGr], [ 40 ] graphene oxide [GO] [ 68 ] ) NDR devices were compared.…”

Classical and quantum phases in hexagonal boron nitride‐combined van der Waals heterostructures

“…NDR near zero bias has been observed only in perfectly aligned WSe 2 /h‐BN/WSe 2 devices, supporting that NDR near zero bias is related to spin and valley properties of WSe 2. 66 Very recently, it was demonstrated in a TMDC/h‐BN/TMDC/Gr‐based RTT 67 that NDR occurs when the applied bias is close to the bandgap of the TMDC (Figure 3H). Therefore, resonant tunneling spectroscopy can be used to probe the bandgap of TMDCs without quasiparticle effects.…”