Termination-dependent topological surface states of the natural superlattice phase Bi${}_{4}$Se${}_{3}$

Editors' Suggestion
Rapid Communication

Termination-dependent topological surface states of the natural superlattice phase Bi $_{4}$ Se $_{3}$

Q. D. Gibson, L. M. Schoop, A. P. Weber, Huiwen Ji, S. Nadj-Perge, I. K. Drozdov, H. Beidenkopf, J. T. Sadowski, A. Fedorov, A. Yazdani, T. Valla, and R. J. Cava

Phys. Rev. B 88, 081108(R) – Published 30 August 2013

Abstract

We describe the topological surface states of Bi $_{4}$ Se $_{3}$ , a compound in the infinitely adaptive Bi $_{2}$ -Bi $_{2}$ Se $_{3}$ natural superlattice phase series, determined by a combination of experimental and theoretical methods. Two observable cleavage surfaces, terminating at Bi or Se, are characterized by angle-resolved photoelectron spectroscopy and scanning tunneling microscopy, and modeled by ab initio density functional theory calculations. Topological surface states are observed on both surfaces, but with markedly different dispersions and Kramers point energies. Bi $_{4}$ Se $_{3}$ therefore represents the only known compound with different topological states on differently terminated, easily distinguished and stable surfaces.

Received 18 April 2013

DOI:https://doi.org/10.1103/PhysRevB.88.081108

Authors & Affiliations

Q. D. Gibson¹, L. M. Schoop¹, A. P. Weber^2,3, Huiwen Ji¹, S. Nadj-Perge⁴, I. K. Drozdov⁴, H. Beidenkopf⁴, J. T. Sadowski⁵, A. Fedorov⁶, A. Yazdani⁴, T. Valla⁷, and R. J. Cava^1,*

¹Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
²National Synchrotron Light Source, Brookhaven National Lab, Upton, New York 11973, USA
³Department of Physics and Astronomy, University of Missouri-Kansas City, Kansas City, Missouri 64110, USA
⁴Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
⁵Center for Functional Nanomaterials, Brookhaven National Lab, Upton, New York 11973, USA
⁶Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
⁷Condensed Matter Physics and Materials Science Department, Brookhaven National Lab, Upton, New York 19973, USA

^*rcava@princeton.edu

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 88, Iss. 8 — 15 August 2013

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Unit cell of Bi $_{4}$ Se $_{3}$ projected down the $a$ axis. Bi-Se polyhedra are shaded to highlight the alternating quintuple layer-bilayer structure. (b) Micro-XPS spectra for the Bi $5 d$ core level, taken from Bi $_{2}$ and Bi $_{2}$ Se $_{3}$ regions, respectively; spot size 2 micrometers. (c) PEEM images obtained using respective Bi $5 d$ $\frac{5}{2}$ core levels showing high intensity (bright) for the Se termination (top) and for the Bi termination (bottom). The field of view is 30 micrometers. The average domain size of the different terminations is approximately equivalent. (d) STM line-cut across a step edge showing the heights of the Bi $_{2}$ and Bi $_{2}$ Se $_{3}$ steps (4 and 8 Å, respectively). (e) False color STM topography image close to the step edge from (d) where both types of surfaces can be identified.Reuse & Permissions
Figure 2
(a) Raw ARPES data for cleavage surfaces dominated by Se termination (left) and Bi termination (right). (b) Photoemission spectra of Se $3 d$ and Bi $3 d$ levels used to identify Bi $_{2}$ Se $_{3}$ - and Bi $_{2}$ -rich regions. (c) Calculated surface electronic structure for the Bi $_{2}$ Se $_{3}$ -terminated (left) and Bi $_{2}$ -terminated (right) surfaces of Bi $_{4}$ Se $_{3}$ . Bulk bands are shaded. (d) Calculated surface electronic structures of Bi $_{2}$ Se $_{3}$ - (left) and Bi $_{2}$ - (right) terminated surfaces, overlaid on the surface states observed experimentally by ARPES, on the same scale.Reuse & Permissions
Figure 3
(a) The calculated electronic structure of weakly coupled Bi $_{2}$ and Bi $_{2}$ Se $_{3}$ layers. Both $F$ and $L$ would project to $\bar{M}$ in the surface electronic structure. The parities of the relevant bands are noted in the superscript. The Bi $_{2}$ -based valence bands and the Bi $_{2}$ Se $_{3}$ -based conduction band are shaded in red and blue, respectively. (b) The calculated surface-state electronic structure for the Bi $_{2}$ -terminated surface of Bi $_{4}$ Se $_{3}$ , shown for comparison to the idealized case. Heavier plotting shows the contribution of the Bi $_{2}$ layers. Bulk bands derived mainly from Bi $_{2}$ and Bi $_{2}$ Se $_{3}$ are shaded red and blue, respectively. For both (a) and (b), circle size is proportional to the amount of Bi $_{2}$ bilayer character.Reuse & Permissions
Figure 4
(a), (d) The ARPES intensity slices corresponding to the Fermi surface ( $E = 0$ meV) and $E = - 75$ meV, respectively. Directions $\bar{Γ} - \bar{M}$ and $\bar{Γ} - \bar{K}$ are along $k_{x}$ and $k_{y}$ , respectively. (b), (e) Symmetrized ARPES data for $E = 0$ and $- 75$ meV. (c), (f) Schematic constant energy contours (CEC)s constructed from comparing the ARPES data with the calculations, for the Bi $_{2}$ termination, presented on the same scale as the symmetrized ARPES data. Red, black, and gray lines are from the Bi $_{2}$ Se $_{3}$ surface states, Bi $_{2}$ surface states, and bulk bands, respectively. Blue and green lines mark the dominant scattering vectors observed in STM. The orange and violet lines mark possible scattering vectors which are present in JDOS but not seen in STM data (see Fig. 5).Reuse & Permissions
Figure 5
(a), (d) Fourier transform of the STM conductance map on the Bi $_{2}$ -terminated surface for $V = 0$ and $- 75$ mV. The color map shows intensities from white-blue (low) to red-black (high). The scattering vectors corresponding to the inner surface structure of the Bi bilayer to the outer bands along the $\bar{Γ} - \bar{M}$ direction is marked by the blue and green lines (compare to Fig. 4). (b), (e) Fourier transform of the STM conductance for the same voltages on the Bi $_{2}$ Se $_{3}$ surface. (c), (f) Joint density of states calculated using ARPES data corresponding to the Fermi surface and $E = - 75$ meV. The blue, green, orange, and violet lines mark the possible scattering vectors (blue and green are seen in STM data, compare also to Fig. 4).Reuse & Permissions

Physical Review B

covering condensed matter and materials physics