Quantum Oscillations in a Two-Dimensional Electron Gas at the Rocksalt/Zincblende Interface of PbTe/CdTe (111) Heterostructures

Abstract

Quantum oscillations are observed in the 2DEG system at the interface of novel heterostructures, PbTe/CdTe (111), with nearly identical lattice parameters (a(PbTe) = 0.6462 nm, a(CdTe) = 0.648 nm) but very different lattice structures (PbTe: rock salt, CdTe: zinc blende). The 2DEG formation mechanism, a mismatch in the bonding configurations of the valence electrons at the interface, is uniquely different from the other known 2DEG systems. The aberration-corrected scanning transmission electron microscope (AC-STEM) characterization indicates an abrupt interface without cation interdiffusion due to a large miscibility gap between the two constituent materials. Electronic transport measurements under magnetic field up to 60 T, with the observation of Landau level filling factor ν = 1, unambiguously reveal a π Berry phase, suggesting the Dirac Fermion nature of the 2DEG at the heterostructure interface, and the PbTe/CdTe heterostructure being a new candidate for 2D topological crystalline insulators.

Electric‐Field Control of Dirac Two‐Dimensional Electron Gas in PbTe/CdTe Heterostructures

“…As illustrated in Figure c, the effective mass can be determined by fitting the temperature dependent SdH amplitudes using the thermal damping factor in the Lifshitz–Kosevich (LK) formula: where k B is Boltzmann constant, ω c = eB / m * is the cyclotron frequency, and T is temperature. The fit gives an m * value as small as 0.0463 m 0 , even smaller than the previous work …”

“…Thin Film Deposition and Device Fabrication : The PbTe/CdTe heterostructures were deposited on freshly cleaved BaF 2 (111) substrate by molecular beam epitaxy system as previous reported . The as‐grown thin film was sculptured with Hall bar configuration (1000 µm in length and 100 µm in width) by standard photolithography and selective wet‐etching.…”

“…Due to their distinctive electronic structures, remarkable physical phenomena that do not occur in the conventional heterostructures have been observed, such as superconductivity, magnetism, and anomalous Hall effect . Recently, we observed quantum oscillation in 2DEGs at the interface of PbTe/CdTe (111) heterostructures, where the primary mechanism is the mismatch in the bonding coordination at the interface, distinctly different from the other 2DEG systems with same crystal symmetry and similar lattice constant but different band gap . A π‐Berry phase is unambiguously revealed by quantum transport, demonstrating the Dirac fermion nature of the topological surface states.…”

Ultrahigh‐Detectivity Photodetectors with Van der Waals Epitaxial CdTe Single‐Crystalline Films

“…Open‐circuit voltage of over 1 V and conversion efficiency of 17% were obtained in monocrystalline CdTe film solar cells . Moreover, 2D electron gas and the quantum hall effect at well‐defined interfaces of CdTe heterostructures such as PbTe/CdTe and HgTe/CdTe provide great potential for application in high‐electron‐mobility transistors . To develop flexible and wearable electronic devices and eliminate the rigid requirement of lattice matching between the substrate and epitaxial material, CdTe has been grown on 2D layered materials through vdWE.…”

Electronic band structure of epitaxial PbTe (111) thin films observed by angle-resolved photoemission spectroscopy

“…Recently, Fu et al theoretically predicted that PbTe could become a topological crystalline insulator by applying pressure, strain or forming an alloy with SnTe [9]. A twodimensional electron gas (2DEG) with high mobility has been discovered by Zhang et al at the interface of rock-salt PbTe and II-VI zinc-blende CdTe, and the quantum oscillation measurements demonstrated the Dirac fermion nature of the 2DEG [10].…”