Nearly-free-electron system of monolayer Na on the surface of single-crystal 
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Eknapakul, Tanachat; Fongkaew, Ittipon; Siriroj, S.; Vidyasagar, R.; Denlinger, Jonathan D.; Bawden, L.; Mo, S.-K.; King, P. D. C.; Takagi, H.; Limpijumnong, Sukit; Meevasana, W.

doi:10.1103/physrevb.94.201121

Cited by 10 publications

(13 citation statements)

References 47 publications

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“…A recurrent question in the study of alkali-metal dosed surfaces of 2D materials is whether the dosed atoms remain on the surface and set up a vertical electric field, or intercalate into the sample [1][2][3][4][6][7][8][9][10][11][12][13][38][39][40][41][42]. A number of recent studies on TMDCs and similar materials have claimed that the alkali metal atoms remain on the surface [2][3][4][5][6]8,9,42], in the case that the sample remains at low temperatures throughout.…”

Section: Resultsmentioning

confidence: 99%

Bulk and surface electronic states in the dosed semimetallic HfTe2

et al. 2020

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The dosing of layered materials with alkali metals has become a commonly used strategy in ARPES experiments. However, precisely what occurs under such conditions, both structurally and electronically, has remained a matter of debate. Here we perform a systematic study of 1T-HfTe 2 , a prototypical semimetal of the transition metal dichalcogenide family. By utilizing photon energy-dependent angle-resolved photoemission spectroscopy (ARPES), we have investigated the electronic structure of this material as a function of potassium (K) deposition. From the k z maps, we observe the appearance of 2D dispersive bands after electron dosing, with an increasing sharpness of the bands, consistent with the wave-function confinement at the topmost layer. In our highest-dosing cases, a monolayerlike electronic structure emerges, presumably as a result of intercalation of the alkali metal. Here, by bringing the topmost valence band below E F , we can directly measure a band overlap of ∼0.2 eV. However, 3D bulklike states still contribute to the spectra even after considerable dosing. Our work provides a reference point for the increasingly popular studies of the alkali metal dosing of semimetals using ARPES.

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Section: Resultsmentioning

confidence: 99%

Bulk and surface electronic states in the dosed semimetallic HfTe2

et al. 2020

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“…Rb was deposited on the cleaved surface, again at the measurement temperature, using a well-outgassed SAES Rb getter source operated at 5.6 A. From analysis of integrated spectral weight of Rb 4p, Pt 4f and Se 3d core-levels as measured by x-ray photoemission spectroscopy (hν = 150 eV), as well as the lack of any free-electron gas states observed in ARPES arXiv:1812.04485v2 [cond-mat.mtrl-sci] 25 Feb 2019 associated with formation of monolayer Rb islands [30], we conclude that the coverage was sub-monolayer.…”

Section: Methodsmentioning

confidence: 99%

Dual quantum confinement and anisotropic spin splitting in the multivalley semimetal PtSe2

et al. 2019

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We investigate the electronic structure of a two-dimensional electron gas created at the surface of the multi-valley semimetal 1T-PtSe2. Using angle-resolved photoemission and first-principles-based surface space charge calculations, we show how the induced quantum well subband states form multiple Fermi surfaces which exhibit highly anisotropic Rashba-like spin splittings. We further show how the presence of both electron-and hole-like bulk carriers causes the near-surface band bending potential to develop an unusual non-monotonic form, with spatially-segregated electron accumulation and hole accumulation regions, which in turn amplifies the induced spin splitting. Our results thus demonstrate the novel environment that semimetals provide for tailoring electrostatically-induced potential profiles and their corresponding quantum subband states.

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“…Dispersive nearly free electron (NFE) states on material surfaces have drawn persistent interest in the past years, due to the remarkable electron transport properties and potential applications in electron emitters. [1][2][3][4][5][6][7] NFE states are usually unoccupied states, with typically parabolic energy dispersion characterized by an effective mass nearly identical to the free electron mass (me), [8][9][10] and widely exist on low-dimensional materials due to the confinement potential normal to the surface, such as twodimensional (2D) graphite, 11,12 graphene, 13 transition-metal dichalcogenides, 14 onedimensional (1D) nanoribbons and nanotubes, 15,16 and even zero-dimensional C60 molecules. 3,17 Moreover, these NFE states are usually extended in the vacuum region above the material surfaces rather than reside at the basal plane, which however limits their influences on the transport properties.…”

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confidence: 99%

One-dimensional nearly free electron states in borophene

et al. 2019

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Two-dimensional boron (borophene) is featured by its structural polymorphs and distinct in-plane anisotropy, opening opportunities to achieve tailored electronic properties by intermixing different phases. Here, using scanning tunneling spectroscopy combined with first-principles calculations, delocalized one-dimensional nearly free electron states (NFE) in the (2,3) or β12 borophene sheet on the Ag (111) surface were observed. The NFE states emerge from a line defect in the borophene, manifested as a structural unit of the (2,2) or χ3 sheet, which creates an in-plane potential well that shifts the states toward the Fermi level. The NFE states are held in the 2D plane of borophene, rather than in the vacuum region as observed in other nanostructures. Furthermore the borophene can provide a rare prototype to further study novel NFE behaviors, which may have potential applications on transport or field emission nanodevices based on boron.

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Nearly-free-electron system of monolayer Na on the surface of single-crystal HfSe2

Cited by 10 publications

References 47 publications

Bulk and surface electronic states in the dosed semimetallic HfTe2

Bulk and surface electronic states in the dosed semimetallic HfTe2

Dual quantum confinement and anisotropic spin splitting in the multivalley semimetal PtSe2

One-dimensional nearly free electron states in borophene

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