SearcharxivSearch

arXiv subjects

Zhenghang Zhi

Publications and source records attributed to Zhenghang Zhi.

7 recordsLinked to original sources

Stack of correlated insulating states in bilayer graphene kagome superlattice

Graphene-based systems have emerged as a rich platform for exploring emergent quantum phenomena-including superconductivity, magnetism, and correlated insulating behavior-arising from flat electronic bands that enhance many-body interactions. Realizing such flat bands has thus far relied primarily on moiré graphene superlattices or rhombohedral stacking graphene systems, both of which face challenges in reproducibility and tunability. Here, we introduce an artificial Kagome superlattice in bilayer graphene, engineered via nanopatterning of the dielectric substrate to create a precisely defined and electrostatically tunable periodic potential. Magnetotransport measurements reveal the emergence of a stack of correlated insulating states at moderate superlattice potentials, characteristic of strong electron-electron interactions within Kagome-induced flat bands. As temperature increases, these correlated gaps collapse, signaling the thermal suppression of interaction-driven states. Continuum-model calculations confirm the formation of multiple flat minibands and reproduce the observed evolution of band reconstruction. Our results establish dielectric-patterned graphene superlattices as a robust and controllable architecture for realizing flat-band-induced correlated phenomena beyond moiré systems.

cond-mat.mes-hall

Shubnikov-de Haas quantum oscillations with large spin splitting in highmobility Al0.8Ga0.2Sb/InAs/ Al0.8Ga0.2Sb quantum-well heterostructures

We report the epitaxial growth of high-quality Al0.8Ga0.2Sb-InAs-Al0.8Ga0.2Sb quantum well films featured by high carrier mobility and strong spin-orbit coupling. By appropriately optimizing the Al-to-Ga ratio in the AlGaSb barrier layer, the quantum confinement of the heterostructure is significantlyenhanced, which results in both an ultra-high electron mobility of 924000 cm2/Vs and a giant magnetoresistance ratio of 365000 at low temperatures. Meanwhile, pronounced Shubnikov-deHaas quantum oscillations persist up to 30 K, and their single-frequency feature indicates a well defined Fermi surface without subband mixing in the two-dimensional electron gas channel. Moreover, the large effective g-factor of 12.93 leads to the observation of Zeeman splitting at large magnetic fields. Our results validate the AlGaSb/InAs quantum well heterostructures as a suitable candidate for constructing energy-efficient topological spintronic devices.

cond-mat.mes-hall

Local Detection of Enhanced Hot Electron Scattering in InSb/CdTe Heterostructure Interface

The InSb/CdTe heterojunction structure, characterized by low effective mass and high electron mobility, exhibits interfacial energy band bending, leading to the Rashba spin-orbit coupling effect and nonreciprocal transport, which makes its suitable for spintronic devices with broad applications in logic and storage fields. However, the complex heterojunction interfaces of InSb/CdTe, composed of group III-V and group II-VI semiconductors, are prone to interdiffusion. Therefore, characterization and study of the interfacial properties of InSb/CdTe heterojunctions are crucial for the growth improvement of the InSb/CdTe material system as well as its application in the field of spintronics. In this study, a novel scanning probe microscope, called a scanning noise microscope, was applied to visualize hot electron scattering in InSb/CdTe nano-devices. The results demonstrated that the near-field signal originates from the Coulomb scattering of charged ions on electrons at the interface of the embedded layer heterojunction. This real-space, nondestructive characterization of the heterojunction interface properties offers a new tool for enhancing the performance of heterojunctions.

physics.app-ph

Tunable interfacial Rashba spin-orbit coupling in asymmetric Al$_x$In$_{1-x}$Sb/InSb/CdTe quantum well heterostructures

The manipulation of Rashba-type spin-orbit coupling (SOC) in molecular beam epitaxy-grown Al$_x$In$_{1-x}$Sb/InSb/CdTe quantum well heterostructures is reported. The effective band bending provides robust two-dimensional quantum confinement, while the unidirectional built-in electric field from the asymmetric hetero-interfaces results in pronounced Rashba SOC strength. By tuning the Al concentration in the top Al$_x$In$_{1-x}$Sb barrier layer, the optimal structure with $x = 0.15$ shows the largest Rashba coefficient of 0.23 eV-Angstrom. and the highest low-temperature electron mobility of 4400 cm$^2$/Vs . Quantitative investigations of the weak anti-localization effect further confirm the dominant D'yakonov-Perel (DP) spin relaxation mechanism during charge-to-spin conversion. These findings highlight the significance of quantum well engineering in shaping magneto-resistance responses, and narrow bandgap semiconductor-based heterostructures may offer a reliable platform for energy-efficient spintronic applications.

cond-mat.mtrl-sci

Interplay between moment-dependent and field-driven unidirectional magnetoresistance in CoFeB/InSb/CdTe heterostructures

Magnetoresistance effects are crucial for understanding the charge/spin transport as well as propelling the advancement of spintronic applications. Here we report the coexistence of magnetic moment-dependent (MD) and magnetic field-driven (FD) unidirectional magnetoresistance (UMR) effects in CoFeB/InSb/CdTe heterostructures. The strong spin-orbital coupling of InSb and the matched impedance at the CoFeB/InSb interface warrant a distinct MD-UMR effect at room temperature, while the interaction between the in-plane magnetic field and the Rashba effect at the InSb/CdTe interface induces the marked FD-UMR signal that dominates the high-field region. Moreover, owning to the different spin transport mechanisms, these two types of nonreciprocal charge transport show opposite polarities with respect to the magnetic field direction, which further enable an effective phase modulation of the angular-dependent magnetoresistance. Besides, the demonstrations of both the tunable UMR response and two-terminal spin-orbit torque-driven magnetization switching validate our CoFeB/InSb/CdTe system as a suitable integrated building block for multifunctional spintronic device design.

physics.app-ph

Interfacial Resonance States-Induced Negative Tunneling Magneto-resistance in Orthogonally-Magnetized CoFeB/MgO/CoFeB

Magnetic tunneling junctions (MTJs) are essential for non-volatile magneto-resistive random access memory (MRAM) applications. Here, we report the observation of a large negative tunneling magneto-resistance (TMR) in the CoFeB/MgO/CoFeB system with an orthogonally-magnetized configuration. Through the thickness modulation of the MgO barrier, the negative TMR component can be enhanced up to 20% under a negative voltage bias. Moreover, the tunnel anisotropic magneto-resistance measurements unveil that the negative TMR component likely arises from the interfacial resonance states (IRS) in the minority band of the bottom ferromagnetic layer. Complementary first principle calculations further quantify the IRS location and strength with respect to the Fermi level position. Our work not only confirm the vital role of IRS in the electrical transport of MTJ, but also provide valuable insights for the design of new-generation voltage-controlled MRAM and related spintronic applications.

physics.app-ph

Room Temperature Gate Tunable Non Reciprocal Charge Transport in Lattice Matched InSb/CdTe Heterostructures

The manipulation of symmetry provides an effective way to tailor the physical orders in solid-state systems. With the breaking of both the inversion and time-reversal symmetries, non-reciprocal magneto-transport may emerge in assorted non-magnetic systems to enrich spintronic physics. Here, we report the observation of the uni-directional magneto-resistance (UMR) in the lattice-matched InSb/CdTe film up to room temperature. Benefiting from the strong built-in electric field of $0.13 \mathrm{~V} \cdot \mathrm{nm}^{-1}$ in the hetero-junction region, the resulting Rashba-type spin-orbit coupling and quantum confinement warrant stable angular-dependent second-order charge current with the non-reciprocal coefficient 1-2 orders of magnitude larger than most non-centrosymmetric materials at 298 K. More importantly, this heterostructure configuration enables highly-efficient gate tuning of the rectification response in which the enhancement of the UMR amplitude by 40% is realized. Our results advocate the narrow-gap semiconductor-based hybrid system with the robust two-dimensional interfacial spin texture as a suitable platform for the pursuit of controllable chiral spin-orbit devices and applications.

cond-mat.mes-hall