Magnetic-Field-Tunable Valley-Contrasting Pseudomagnetic Confinement in Graphene

Ren, Ya-Ning; Zhuang, Yu-Chen; Sun, Qing-Feng; He, Lin

doi:10.1103/physrevlett.129.076802

Cited by 15 publications

(9 citation statements)

References 61 publications

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“…When a real external magnetic field is applied, the total effective magnetic fields in the two valleys become imbalanced and the effective magnetic barriers for quasiparticles in the two valleys are different (figure 5(c)). In this way, the valley-contrasting magnetic barriers are achieved and so is valley contrasting spatial confinement, lifting the valley degeneracy of the confined states [37].…”

Section: Magnetic Fieldmentioning

confidence: 99%

Valleytronics in two-dimensional magnetic materials

Luo,

Huang,

Qiao

et al. 2024

J. Phys. Mater.

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Valleytronics uses valleys to encode information. It combines other degrees of freedom to produce a more comprehensive, stable, and efficient information processing system. However, in nonmagnetic valleytronic materials, the valley polarization is transient and the depolarization occurs once the external excitation is withdrawn. Introduction of magnetic field is an effective approach to realizing the spontaneous valley polarization by breaking the time-reversal symmetry. In hexagonal magnetic valleytronic materials, the inequivalent valleys at the K and -K Dirac cones have asymmetric energy gaps and Berry curvatures. The time-reversal symmetry in nonmagnetic materials can be broken by applying an external magnetic field, adding a magnetic substrate or doping magnetic atoms. Recent theoretical studies have demonstrated that valleytronic materials with intrinsic ferromagnetism, now termed as ferrovalley materials, exhibit spontaneous valley polarization without the need for external fields to maintain the polarization. The coupling of the valley and spin degrees of freedom enables stable and unequal distribution of electrons in the two valleys and thus facilitating nonvolatile information storage. Hence, ferrovalley materials are promising materials for valleytronic devices. In this review, we first briefly overview valleytronics and its related properties, the ways to realize valley polarization in nonmagnetic valleytronic materials. Then we focus on the recent developments in two-dimensional ferrovalley materials, which can be classified according to their molecular formula and crystal structure: MX2; M(XY)2, M(XY2) and M(XYZ)2; M2X3, M3X8 and MNX6; MNX2Y2, M2X2Y6 and MNX2Y6; and the Janus structure ferrovalley materials. In the inequivalent valleys, the Berry curvatures have opposite signs with unequal absolute values, leading to anomalous valley Hall effect. When the valley polarization is large, the ferrovalleys can be selectively excited even with unpolarized light. Intrinsic valley polarization in two-dimensional ferrovalley materials is of great importance. It opens a new avenue for information-related applications and hence is under rapid development.

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Section: Magnetic Fieldmentioning

confidence: 99%

Valleytronics in two-dimensional magnetic materials

Luo,

Huang,

Qiao

et al. 2024

J. Phys. Mater.

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“…STS spectra are taken at AA, AB and BA regions and marked in the corresponding areas in the STM image [72] of Fig. 8(c)) [82]. By combining real magnetic fields and PMFs, the total effective magnetic fields in two valleys become imbalanced; the K valley has a higher effective magnetic field, which leads to a shorter effective magnetic con-fined length and a larger energy spacing, and the K valley has a lower magnetic field, resulting in a longer effective magnetic confined length and a smaller energy spacing, thus causing a valley splitting in pseudomagnetic confine- ment regions (bottom panel of Fig.…”

Section: Single-to-periodic Strained Structuresmentioning

confidence: 99%

Recent progresses on graphene-based artificial nanostructures: a perspective from scanning tunneling microscopy

Liu

2023

Quantum Front

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Graphene, a Dirac semimetal, exhibits the simplest lattice configuration and band structure in the world of two-dimensional materials. Due to its remarkable brevity and tunability, graphene becomes an ideal platform for studying the fundamental physics arising from the linear dispersion around the Dirac point, as well as for exploring symmetry-breaking orders in the flat band through playing with various artificial structures and external fields. In this review, we provide an overview of the nanoscale graphene model structures such as defects, quantum dots, strains, and superlattices in scanning tunneling microscopy measurements. Utilizing nanostructures in diverse dimensions, we present some behaviors of electrons near singularities of density of states from the perspective of scanning tunneling microscopy.

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“…For example, while a real magnetic field B R splits spin polarised states, a pseudo-magnetic field B s does not split valley polarised states [46]. Some types of strain can be employed to control the valley pseudospin of graphene's carriers [112,[115][116][117][118]. Depicted in figure 5, one method involves the combination of straininduced pseudo-magnetic fields B s and real magnetic fields B R [116,117].…”

Section: Cut and Folded Graphene: Sublattice And Valley Polarisationmentioning

confidence: 99%

Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update

Naumis,

Herrera,

Poudel

et al. 2023

Rep. Prog. Phys.

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This is an update of a previous review on the subject \cite{Naumis_2017}. Experimental and theoretical advances for straining graphene and other metallic, insulating, ferroelectric, ferroelastic, ferromagnetic and multiferroic 2D materials have been considered. Specific topics of discussion include: (i) methods to induce valley and sublattice polarisation ($\mathbf{P}$) in graphene, (ii) time-dependent strain and its impact on graphene's electronic properties, (iii) the role of local and global strain on superconductivity and other highly correlated and/or topological phases of graphene, inducing polarisation $\mathbf{P}$ on hexagonal boron nitride monolayers {\it via} strain, (iv) measuring strain, and modifying through strain the optoelectronic properties of transition metal dichalcogenides, (v) ferroic 2D materials with intrinsic elastic ($\sigma$), electric ($\mathbf{P}$) and magnetic ($\mathbf{M}$) polarisation under strain, as well as incipient 2D multiferroics and (vi) moir'e bilayers exhibiting flat electronic bands and exotic quantum phase diagrams, and other bilayer or few-layer systems exhibiting ferroic orders tunable by rotations and shear strain. The review features the extremely recent experimental realizations of a tunable two-dimensional Quantum Spin Hall effect in germanene, of monoelemental 2D ferroelectric bismuth, and 2D multiferroic NiI$_2$. The document was structured for a discussion of effects taking place in monolayers first, followed by discussions concerning bilayers and few-layers, and it represents a fresh and up-to-date overview of exciting and newest developments on the fast-paced field of 2D materials.

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Magnetic-Field-Tunable Valley-Contrasting Pseudomagnetic Confinement in Graphene

Cited by 15 publications

References 61 publications

Valleytronics in two-dimensional magnetic materials

Valleytronics in two-dimensional magnetic materials

Recent progresses on graphene-based artificial nanostructures: a perspective from scanning tunneling microscopy

Mechanical, electronic, optical, piezoelectric and ferroic properties of strained graphene and other strained monolayers and multilayers: an update

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