Electric field tunable magnetoexcitons in Xenes-hBN-TMDC, Xenes-hBN-BP, and Xenes-hBN-TMTC heterostructures

TL;DR

The paper investigates van der Waals heterostructures composed of Xenes, hBN, TMDCs, phosphorene, and TMTCs to host Rydberg indirect magnetoexcitons under perpendicular electric $E_{ot}$ and magnetic $B$ fields. Using a Mott–Wannier framework with anisotropic in-plane masses, it demonstrates that exciton binding energies and reduced masses can be tuned by $E_{ot}$ and by the number of hBN spacers, with dielectric screening attenuating BE. Anisotropic layers (BP and TMTCs) display direction-dependent responses in BE and diamagnetic coefficients, which themselves decrease with $E_{ot}$ but rise with more hBN layers. The work further proposes Floquet-band engineering via time-periodic $E_{ot}(t)$ to dynamically tailor the excitonic band structure, highlighting potential routes to advanced optoelectronic and quantum devices based on controllable magnetoexcitons in 2D heterostructures.

Abstract

In this work, we propose novel van der Waals (vdW) heterostructures composed of Xenes, transition metal dichalcogenides (TMDCs), phosphorene, and transition metal trichalcogenides (TMTCs), which are separated by insulating hexagonal boron nitride (hBN) layers. We investigate theoretically the behavior of Rydberg indirect excitons in Xenes-hBN-TMDC, Xenes-hBN-BP, and Xenes-hBN-TMTC heterostructures, subject to parallel external electric and magnetic fields that are oriented perpendicular to the layers. By incorporating both isotropic and anisotropic materials, we demonstrate that excitonic properties can be effectively tuned through the external field strengths and the heterostructure design. Our results show that the exciton reduced mass and the binding energy increase with the electric field strength, while enhanced dielectric screening from additional hBN layers reduces the binding energy. Anisotropic materials exhibit distinct excitonic responses, including variations in diamagnetic behavior. Moreover, the diamagnetic energy contributions and coefficients decrease with stronger electric fields but increase with the number of hBN layers. Finally, we explore the potential of time-periodic electric fields with Floquet band-structure engineering. These findings provide a comprehensive framework for controlling excitonic phenomena in low-dimensional materials, enabling the design of advanced optoelectronic and quantum devices.

Figures (6)

• Figure 1: (Color online) Schematic illustration of excitons in ($a$) Xenes/hBN/TMDC and ($b$) Xenes/hBN/BP van der Waals heterostructure in electric and magnetic fields. By replacing phosphorene by TMTC monolayer one gets Xenes/hBN/TMTC heterostructure.
• Figure 2: (Color online) The dependence of the reduced mass of an exciton in Xenes/TMDC ($a$) and Xenes/BP ($b$) heterostructures on the electric field. In calculations, we used masses of holes in WS$_{2}$ and BP monolayers from Kylanpaa2015 and Peng2014, respectively.
• Figure 3: (Color online) The electric-field dependence of the binding energies of an exciton in the Rydberg state 1$s$ for $(a)$ Si/hBN/MoSe$_2$ and $(b)$ Si/hBN/BP heterostructures. The number of dielectric layers, hBN, is given for $N$ = 1, 6. In calculations, we used masses of holes and thicknesses of MoS$_{2}$ and BP monolayers from Ramasubramaniam2012 and Kylanpaa2015, and Peng2014 and Kumar2016, respectively.
• Figure 4: (Color online) The dependence of the total potentials $W_{1}(x,y)=\frac{e^{2}}{8\mu _{x}}B^{2}x^{2}+\frac{e^{2}}{8\mu _{y}}B^{2}y^{2}+V(x,y)$ and $W_{2}(x,y)=\frac{e^{2}}{8\mu }B^{2}(x^{2}+y^{2})+V(x,y)$ acting on the electron-hole pair in Xenes/BP (Si/BP) and Xenes/TMDC (Si/WS$_{2}$) ($a$) and Xenes/TMTC (Si/ZrS$_{3}$) and Xenes/TMDC (Si/WS$_{2}$) $b$) heterostructures. Calculations are performed for the electron-hole pair in the external magnetic field $B=30$ T and electric field $E_{\perp}=0.1$ V/Å.
• Figure 5: (Color online) Dependence of energy $\Delta E$ for magnetoexcitons in $1s$ and $3s$ states in Xenes/MoSe$_2$ and Xenes/hBN/BP heterostructures on the electric and magnetic fields. In calculations, we used parameters summarized in Table \ref{['Imputtable']}.