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Angle-resolved photoemission spectroscopy study on the surface states of the correlated topological insulator YbB6.

Xia M, Jiang J, Ye ZR, Wang YH, Zhang Y, Chen SD, Niu XH, Xu DF, Chen F, Chen XH, Xie BP, Zhang T, Feng DL - Sci Rep (2014)

Bottom Line: Circular dichroism photoemission spectra suggest that these in-gap states possess chirality of orbital angular momentum, which is related to the chiral spin texture, further indicative of their topological nature.The observed insulating gap of YbB6 is about 100 meV, larger than that found by theoretical calculations.Our results present strong evidence that YbB6 is a correlated topological insulator and provide a foundation for further studies of this promising material.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China [2].

ABSTRACT
YbB6 is recently predicted to be a moderately correlated topological insulator, which provides a playground to explore the interplay between correlation and topological properties. With angle-resolved photoemission spectroscopy, we directly observed almost linearly dispersive bands around the time-reversal invariant momenta and with negligible kz dependence, consistent with odd number of surface states crossing the Fermi level in a Z2 topological insulator. Circular dichroism photoemission spectra suggest that these in-gap states possess chirality of orbital angular momentum, which is related to the chiral spin texture, further indicative of their topological nature. The observed insulating gap of YbB6 is about 100 meV, larger than that found by theoretical calculations. Our results present strong evidence that YbB6 is a correlated topological insulator and provide a foundation for further studies of this promising material.

No MeSH data available.


Related in: MedlinePlus

Circular Dichroism of the surface states around  and .(a) Fermi surface maps of YbB6 taken with RCP, LCP light and their difference (RCP-LCP) of S1. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. (b) The RCP-LCP data around  enlarged from panel (a). (c) Top: CD result of S4 (top) and S5 (bottom) measured with 35 eV photons showing the right  pocket and the left  pocket, respectively. (d) The CD values taken along the left pocket around  in panel (a) of S1 as a function of the polar angle Ω. Ω is defined within panel (a) respect to . (e) The same as that in panel (d) to show the CD of α pocket taken on S4, where Ω is defined within panel (c) respect to . The red solid curves in panel (d) and (e) are sine function fits of the data. The 31 eV data were taken at 6 K in SSRL and the 35 eV data were taken at 18 K in SLS.
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f4: Circular Dichroism of the surface states around and .(a) Fermi surface maps of YbB6 taken with RCP, LCP light and their difference (RCP-LCP) of S1. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. (b) The RCP-LCP data around enlarged from panel (a). (c) Top: CD result of S4 (top) and S5 (bottom) measured with 35 eV photons showing the right pocket and the left pocket, respectively. (d) The CD values taken along the left pocket around in panel (a) of S1 as a function of the polar angle Ω. Ω is defined within panel (a) respect to . (e) The same as that in panel (d) to show the CD of α pocket taken on S4, where Ω is defined within panel (c) respect to . The red solid curves in panel (d) and (e) are sine function fits of the data. The 31 eV data were taken at 6 K in SSRL and the 35 eV data were taken at 18 K in SLS.

Mentions: The Fermi surface maps of S1 measured under right-handed circular polarized (RCP) light and left-handed circular polarized (LCP) light are shown in Fig. 4(a), together with their difference (referred to as RCP-LCP). The CD of the β pocket shows an anti-symmetric pattern about the axis in the surface BZ. The enlarged CD image near is shown in Fig. 4(b). Although its intensity is much weaker than that of the β pocket, we can see that the symmetry of the α pocket becomes two-fold, which is different from the anti-symmetric CD pattern of the β pocket. Such symmetries are confirmed by another set of data with more statistics in the top panel of Fig. 4(c), which was measured on S4 with 35 eV photons, showing the α pocket and the right β pocket. The bottom panel in Fig. 4c is measured on sample 5 (S5), under the same condition as S2, but presents the left β pocket. Clearly, all the CD patterns exhibit an inversion symmetry with respect to .


Angle-resolved photoemission spectroscopy study on the surface states of the correlated topological insulator YbB6.

Xia M, Jiang J, Ye ZR, Wang YH, Zhang Y, Chen SD, Niu XH, Xu DF, Chen F, Chen XH, Xie BP, Zhang T, Feng DL - Sci Rep (2014)

Circular Dichroism of the surface states around  and .(a) Fermi surface maps of YbB6 taken with RCP, LCP light and their difference (RCP-LCP) of S1. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. (b) The RCP-LCP data around  enlarged from panel (a). (c) Top: CD result of S4 (top) and S5 (bottom) measured with 35 eV photons showing the right  pocket and the left  pocket, respectively. (d) The CD values taken along the left pocket around  in panel (a) of S1 as a function of the polar angle Ω. Ω is defined within panel (a) respect to . (e) The same as that in panel (d) to show the CD of α pocket taken on S4, where Ω is defined within panel (c) respect to . The red solid curves in panel (d) and (e) are sine function fits of the data. The 31 eV data were taken at 6 K in SSRL and the 35 eV data were taken at 18 K in SLS.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4126005&req=5

f4: Circular Dichroism of the surface states around and .(a) Fermi surface maps of YbB6 taken with RCP, LCP light and their difference (RCP-LCP) of S1. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. (b) The RCP-LCP data around enlarged from panel (a). (c) Top: CD result of S4 (top) and S5 (bottom) measured with 35 eV photons showing the right pocket and the left pocket, respectively. (d) The CD values taken along the left pocket around in panel (a) of S1 as a function of the polar angle Ω. Ω is defined within panel (a) respect to . (e) The same as that in panel (d) to show the CD of α pocket taken on S4, where Ω is defined within panel (c) respect to . The red solid curves in panel (d) and (e) are sine function fits of the data. The 31 eV data were taken at 6 K in SSRL and the 35 eV data were taken at 18 K in SLS.
Mentions: The Fermi surface maps of S1 measured under right-handed circular polarized (RCP) light and left-handed circular polarized (LCP) light are shown in Fig. 4(a), together with their difference (referred to as RCP-LCP). The CD of the β pocket shows an anti-symmetric pattern about the axis in the surface BZ. The enlarged CD image near is shown in Fig. 4(b). Although its intensity is much weaker than that of the β pocket, we can see that the symmetry of the α pocket becomes two-fold, which is different from the anti-symmetric CD pattern of the β pocket. Such symmetries are confirmed by another set of data with more statistics in the top panel of Fig. 4(c), which was measured on S4 with 35 eV photons, showing the α pocket and the right β pocket. The bottom panel in Fig. 4c is measured on sample 5 (S5), under the same condition as S2, but presents the left β pocket. Clearly, all the CD patterns exhibit an inversion symmetry with respect to .

Bottom Line: Circular dichroism photoemission spectra suggest that these in-gap states possess chirality of orbital angular momentum, which is related to the chiral spin texture, further indicative of their topological nature.The observed insulating gap of YbB6 is about 100 meV, larger than that found by theoretical calculations.Our results present strong evidence that YbB6 is a correlated topological insulator and provide a foundation for further studies of this promising material.

View Article: PubMed Central - PubMed

Affiliation: 1] State Key Laboratory of Surface Physics, Department of Physics, and Advanced Materials Laboratory, Fudan University, Shanghai 200433, China [2].

ABSTRACT
YbB6 is recently predicted to be a moderately correlated topological insulator, which provides a playground to explore the interplay between correlation and topological properties. With angle-resolved photoemission spectroscopy, we directly observed almost linearly dispersive bands around the time-reversal invariant momenta and with negligible kz dependence, consistent with odd number of surface states crossing the Fermi level in a Z2 topological insulator. Circular dichroism photoemission spectra suggest that these in-gap states possess chirality of orbital angular momentum, which is related to the chiral spin texture, further indicative of their topological nature. The observed insulating gap of YbB6 is about 100 meV, larger than that found by theoretical calculations. Our results present strong evidence that YbB6 is a correlated topological insulator and provide a foundation for further studies of this promising material.

No MeSH data available.


Related in: MedlinePlus