Limits...
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

Photon energy dependence of the α, β and γ bands.(a, b) Photon energy dependence of the photoemission intensity of the α band measured along cut 2 on S4 and its corresponding MDC plots within [EF -200 meV, EF]. (c, d) The same for the β band as in panel (a) and (b) measured along cut 3 on S4. (e, f) Photon energy dependence of the photoemission intensity of the γ band measured along cut 2 on S2 and its corresponding MDC plots within [EF -600 meV, EF -360 meV]. The data in panel (e) is subtracted by a momentum-independent background. The spectra far away from the dispersive region show no momentum dependence, and thus they are taken as the background. The red dashed lines in panel (b), (d) and (f) are fitted dispersions with 94 eV data of the α and β bands and with 103 eV data of the γ band, respectively, and overlaid them onto the data of other photon energies. The white dashed lines in panel (e) are extracted from the 103 eV data indicating the α and γ bands, and overlaid them on top of data with other photon energies. (g–j) Photoemission intensity plots in the kz-kx plane at EF, EF-150 meV, EF-450 meV, EF-600 meV, respectively. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. The red dashed lines indicate the dispersions of the α, β and γ bands along kz direction. Data were taken at 18 K in SLS.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4126005&req=5

f3: Photon energy dependence of the α, β and γ bands.(a, b) Photon energy dependence of the photoemission intensity of the α band measured along cut 2 on S4 and its corresponding MDC plots within [EF -200 meV, EF]. (c, d) The same for the β band as in panel (a) and (b) measured along cut 3 on S4. (e, f) Photon energy dependence of the photoemission intensity of the γ band measured along cut 2 on S2 and its corresponding MDC plots within [EF -600 meV, EF -360 meV]. The data in panel (e) is subtracted by a momentum-independent background. The spectra far away from the dispersive region show no momentum dependence, and thus they are taken as the background. The red dashed lines in panel (b), (d) and (f) are fitted dispersions with 94 eV data of the α and β bands and with 103 eV data of the γ band, respectively, and overlaid them onto the data of other photon energies. The white dashed lines in panel (e) are extracted from the 103 eV data indicating the α and γ bands, and overlaid them on top of data with other photon energies. (g–j) Photoemission intensity plots in the kz-kx plane at EF, EF-150 meV, EF-450 meV, EF-600 meV, respectively. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. The red dashed lines indicate the dispersions of the α, β and γ bands along kz direction. Data were taken at 18 K in SLS.

Mentions: Photon energy dependent ARPES experiments have been performed to examine how the α, β and γ bands vary with kz. The photoemission intensity distributions taken with different photon energies are presented in Fig. 3. One can see that, for both α and β bands, although the spectral weight varies with photon energy due to photoemission matrix element effects, the dispersions of them remain unchanged. Figures 3(a) and 3(b) show the photoemission intensity distributions across on sample 4 (S4) together with their corresponding MDCs. We fitted the dispersion of the α band taken with 94 eV photons and overlaid it onto the data taken with several other photon energies, which clearly show that the dispersion of α is kz independent. The same process has been done to the β band in Figs. 3(c) and 3(d), which also show no kz dependence. More data under other photon energies can be found in the Supplementary Information (SI).


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)

Photon energy dependence of the α, β and γ bands.(a, b) Photon energy dependence of the photoemission intensity of the α band measured along cut 2 on S4 and its corresponding MDC plots within [EF -200 meV, EF]. (c, d) The same for the β band as in panel (a) and (b) measured along cut 3 on S4. (e, f) Photon energy dependence of the photoemission intensity of the γ band measured along cut 2 on S2 and its corresponding MDC plots within [EF -600 meV, EF -360 meV]. The data in panel (e) is subtracted by a momentum-independent background. The spectra far away from the dispersive region show no momentum dependence, and thus they are taken as the background. The red dashed lines in panel (b), (d) and (f) are fitted dispersions with 94 eV data of the α and β bands and with 103 eV data of the γ band, respectively, and overlaid them onto the data of other photon energies. The white dashed lines in panel (e) are extracted from the 103 eV data indicating the α and γ bands, and overlaid them on top of data with other photon energies. (g–j) Photoemission intensity plots in the kz-kx plane at EF, EF-150 meV, EF-450 meV, EF-600 meV, respectively. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. The red dashed lines indicate the dispersions of the α, β and γ bands along kz direction. 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

f3: Photon energy dependence of the α, β and γ bands.(a, b) Photon energy dependence of the photoemission intensity of the α band measured along cut 2 on S4 and its corresponding MDC plots within [EF -200 meV, EF]. (c, d) The same for the β band as in panel (a) and (b) measured along cut 3 on S4. (e, f) Photon energy dependence of the photoemission intensity of the γ band measured along cut 2 on S2 and its corresponding MDC plots within [EF -600 meV, EF -360 meV]. The data in panel (e) is subtracted by a momentum-independent background. The spectra far away from the dispersive region show no momentum dependence, and thus they are taken as the background. The red dashed lines in panel (b), (d) and (f) are fitted dispersions with 94 eV data of the α and β bands and with 103 eV data of the γ band, respectively, and overlaid them onto the data of other photon energies. The white dashed lines in panel (e) are extracted from the 103 eV data indicating the α and γ bands, and overlaid them on top of data with other photon energies. (g–j) Photoemission intensity plots in the kz-kx plane at EF, EF-150 meV, EF-450 meV, EF-600 meV, respectively. The intensity was integrated over a window of [EF - 10 meV, EF + 10 meV]. The red dashed lines indicate the dispersions of the α, β and γ bands along kz direction. Data were taken at 18 K in SLS.
Mentions: Photon energy dependent ARPES experiments have been performed to examine how the α, β and γ bands vary with kz. The photoemission intensity distributions taken with different photon energies are presented in Fig. 3. One can see that, for both α and β bands, although the spectral weight varies with photon energy due to photoemission matrix element effects, the dispersions of them remain unchanged. Figures 3(a) and 3(b) show the photoemission intensity distributions across on sample 4 (S4) together with their corresponding MDCs. We fitted the dispersion of the α band taken with 94 eV photons and overlaid it onto the data taken with several other photon energies, which clearly show that the dispersion of α is kz independent. The same process has been done to the β band in Figs. 3(c) and 3(d), which also show no kz dependence. More data under other photon energies can be found in the Supplementary Information (SI).

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