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Two-dimensional transition metal dichalcogenide (TMD) semiconductors provide a unique possibility to access the electronic valley degree of freedom using polarized light, opening the way to valley information transfer between distant…

The valley degeneracy of electron states in graphene stimulates intensive research of valley-related optical and transport phenomena. While many proposals on how to manipulate valley states have been put forward, experimental access to the…

Mesoscale and Nanoscale Physics · Physics 2014-11-17 L. E. Golub , S. A. Tarasenko

Valleytronics harnesses the valley degree of freedom -- energy-degenerate extrema in the electronic band structure -- for information storage and processing. Valley Hall effect (VHE) is a cornerstone of valleytronics, enabling electric…

Mesoscale and Nanoscale Physics · Physics 2026-03-17 Jin Cao , Shen Lai , Cong Xiao , Qian Niu , Shengyuan A. Yang

For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 Tesla…

Mesoscale and Nanoscale Physics · Physics 2017-06-14 Patrick Back , Meinrad Sidler , Ovidiu Cotlet , Ajit Srivastava , Naotomo Takemura , Martin Kroner , Atac Imamoglu

We introduce the concept of valley-layer coupling (VLC) in two-dimensional materials, where the low-energy electronic states in the emergent valleys have valley-contrasted layer polarization such that each state is spatially localized on…

Mesoscale and Nanoscale Physics · Physics 2020-01-29 Zhi-Ming Yu , Shan Guan , Xian-Lei Sheng , Weibo Gao , Shengyuan A. Yang

By using the first-principles calculations and model analyses, we found that the combination of defected tungsten disulfide monolayer and sparse manganese adsorption may give a KK` valley spin splitting up to 210 meV. This system also has a…

Mesoscale and Nanoscale Physics · Physics 2020-01-22 Jie Li , Lei Gu , Ruqian Wu

While conventional semiconductor technology relies on the manipulation of electrical charge for the implementation of computational logic, additional degrees of freedom such as spin and valley offer alternative avenues for the encoding of…

Anomalous valley Hall (AVH) effect is a fundamental transport phenomenon in the field of condensed-matter physics. Usually, the research on AVH effect is mainly focused on 2D lattices with ferromagnetic order. Here, by means of model…

Materials Science · Physics 2021-07-27 Wenhui Du , Rui Peng , Zhonglin He , Ying Dai , Baibiao Huang , Yandong Ma

We uncover a new origin of the planar Hall effect - as an intrinsic property of layer coherent electrons - that exists even in bilayer and trilayer atomically thin limit. It reforms the existing theories requiring three-dimensional orbital…

Mesoscale and Nanoscale Physics · Physics 2025-06-13 Huiyuan Zheng , Dawei Zhai , Cong Xiao , Wang Yao

Strongly interacting two dimensional electron systems (2DESs) host a complex landscape of broken symmetry states. The possible ground states are further expanded by internal degrees of freedom such as spin or valley-isospin. While direct…

Mesoscale and Nanoscale Physics · Physics 2017-11-01 B. M. Hunt , J. I. A. Li , A. A. Zibrov , L. Wang , T. Taniguchi , K. Watanabe , J. Hone , C. R. Dean , M. Zaletel , R. C. Ashoori , A. F. Young

Underpinning the field of "valleytronics" is the coupling of the helicity of circularly polarized light to the valley degree of freedom, and this remains the only known lightform to exhibit this remarkable effect. Here we show that on…

Optics · Physics 2022-03-29 S. Sharma , P. Elliott , S. Shallcross

The valley dependent optical selection rules in recently discovered monolayer group-VI transition metal dichalcogenides (TMDs) make possible optical control of valley polarization, a crucial step towards valleytronic applications. However,…

Mesoscale and Nanoscale Physics · Physics 2014-07-31 Rui-Lin Chu , Xiao Li , Sanfeng Wu , Qian Niu , Wang Yao , Xiaodong Xu , Chuanwei Zhang

We report magneto-absorption spectroscopy of gated WSe$_2$ monolayers in high magnetic fields up to 60~T. When doped with a 2D Fermi sea of mobile holes, well-resolved sequences of optical transitions are observed in both $\sigma^\pm$…

Mesoscale and Nanoscale Physics · Physics 2020-10-07 Jing Li , Mateusz Goryca , Nathan P. Wilson , Andreas V. Stier , Xiaodong Xu , Scott A. Crooker

The valley splitting, which lifts the degeneracy of the lowest two valley states in a SiO$_2$/(100)Si/SiO$_2$ quantum well is examined through transport measurements. We demonstrate that the valley splitting can be observed directly as a…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 K. Takashina , Y. Ono , A. Fujiwara , Y. Takahashi , Y. Hirayama

In this Letter, a tunable valley polarization is investigated for honeycomb systems with broken inversion symmetry such as transition-metal dichalcogenide MX2 (M = Mo, W; X = S, Se) monolayers through elliptical pumping. As compared to…

Mesoscale and Nanoscale Physics · Physics 2014-11-26 Zhigang Song , Ruge Quhe , Yan Li , Ji Feng , Jing Lu , Jinbo Yang

Electronic and spintronic devices rely on the fact that free charge carriers in solids carry electric charge and spin, respectively. There are, however, other properties of charge carriers that might be exploited in new families of devices.…

Mesoscale and Nanoscale Physics · Physics 2015-06-05 Kin Fai Mak , Keliang He , Jie Shan , Tony F. Heinz

We theoretically investigate spin-valley-locked tunneling transport in a transition-metal dichalcogenide/ferromagnetic-insulator heterostructure under a perpendicular magnetic field, driven by the spin Seebeck effect. We demonstrate that…

Mesoscale and Nanoscale Physics · Physics 2026-02-09 Xin Hu , Yuya Ominato , Mamoru Matsuo

The coherent manipulation of spin and pseudospin underlies existing and emerging quantum technologies, including NMR, quantum communication, and quantum computation. Valley polarization, associated with the occupancy of degenerate, but…

Mesoscale and Nanoscale Physics · Physics 2017-02-01 Ziliang Ye , Dezheng Sun , Tony F. Heinz

Spin-orbit coupling is a fundamental mechanism that connects the spin of a charge carrier with its momentum. Likewise, in the optical domain, a synthetic spin-orbit coupling is accessible, for instance, by engineering optical anisotropies…

We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the K and K' points in singly-oriented single layer WS$_2$/Au(111). Our results reveal…