#
Detection of Surface States in Quantum Materials ZrTe_{2} and TmB_{4} by Scanning Tunneling Microscopy

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## Abstract

**:**

## 1. Introduction

## 2. Samples and Experiments

## 3. Results

#### 3.1. ZrTe_{2}

#### 3.1.1. Topography

#### 3.1.2. Spectroscopy

#### 3.2. TmB_{4}

#### 3.2.1. Topography

#### 3.2.2. Spectroscopy

**Figure 9.**Spectroscopy on TmB${}_{4}$ within the two areas (denoted as S1 and S2) marked by the same color in Figure 6b. Set point: ${V}_{\mathrm{b}}=+$0.8 V, ${I}_{\mathrm{sp}}=$ 0.6 nA.

## 4. Discussion

## Supplementary Materials

## Author Contributions

## Funding

## Institutional Review Board Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Crystalline structure of tetragonal TmB${}_{4}$. (

**a**) View along the $bc$ plane; red: Tm, gray: B octahedra, blue: B dimers. (

**b**) Tm plane visualizing the combination of square and triangular arrangements. (

**c**) B atoms in the $ab$ plane. All panels share the same color code, with one unit cell marked in gray.

**Figure 2.**Topography overview of cleaved ZrTe${}_{2}$ over an area of $20\times 16$ nm${}^{2}$ obtained in dual bias mode, i.e., the two images show exactly the same sample area. (

**a**) ${V}_{\mathrm{b}}=+$0.6 V visualizing empty states and (

**b**) ${V}_{\mathrm{b}}=-$0.6 V, occupied states; ${I}_{\mathrm{sp}}=$ 200 pA in both cases. Two different types of defects can be recognized: Single-site vacancies and triangularly shaped defects extending over several lattice sites. The total height range of both topographies is 66 pm.

**Figure 3.**(

**a**) Atomically resolved, mostly defect−free area of $5\times 5$ nm${}^{2}$ on ZrTe${}_{2}$. ${V}_{\mathrm{b}}=+$0.6 V, ${I}_{\mathrm{sp}}=$ 200 pA. (

**b**) Height profile obtained along the blue line marked in (a).

**Figure 4.**(

**a**) Tunneling spectroscopy on a surface of ZrTe${}_{2}$. The inset shows a zoom into the low−energy range of −0.15 V $\le {V}_{\mathrm{b}}\le $+0.15 V. Spectra were averaged over the total (blue) area and within the red rectangle. (

**b**) Topography of total area $6.2\times 6.2$ nm${}^{2}$ studied to obtain the spectra in (

**a**); ${V}_{\mathrm{b}}=+$0.6 V, ${I}_{\mathrm{sp}}=$ 200 pA. The area of the red rectangle ($4.2\times 3.2$ nm${}^{2}$) is largely free of defects.

**Figure 5.**Calculated band structure (

**left**) and density of states (

**right**) for ZrTe${}_{2}$. Figure reproduced from [49].

**Figure 6.**(

**a**) Topography overview of cleaved TmB${}_{4}$ over an area of $200\times 200$ nm${}^{2}$ exhibiting several terraces; ${V}_{\mathrm{b}}=+$0.4 V, ${I}_{\mathrm{sp}}=$ 600 pA. (

**b**) Zoom into one terrace within the $ab$ plane, area $60\times 60$ nm${}^{2}$, ${V}_{\mathrm{b}}=+$0.8 V, ${I}_{\mathrm{sp}}=$ 600 pA, total height range 770 pm. Numerous individual defects are visible. Green and blue rectangles mark areas within which spectroscopy was conducted, see Figure 9. (

**c**) Height scan along the blue line marked in (

**a**). The heights of the step edges of about 0.41 nm correspond to the lattice constant $c=$ 0.398 nm.

**Figure 7.**Topography (

**left**) on TmB${}_{4}$ of type A; area of $5\times 5$ nm${}^{2}$, ${V}_{\mathrm{b}}=+$0.15 V, ${I}_{\mathrm{sp}}=$ 600 pA.

**Right**: Height scans along the lines of corresponding color marked in the topography. The average distance between protrusions is ∼0.5 nm.

**Figure 8.**Atomically resolved surface topography type B (

**left**) of TmB${}_{4}$; area of $10\times 10$ nm${}^{2}$, ${V}_{\mathrm{b}}=+$0.4 V, ${I}_{\mathrm{sp}}=$ 600 pA.

**Right**: Height scans along the lines of corresponding color marked in the topography. The average distance between protrusions is ∼0.7 nm.

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**MDPI and ACS Style**

Ale Crivillero, M.V.; Souza, J.C.; Hasse, V.; Schmidt, M.; Shitsevalova, N.; Gabáni, S.; Siemensmeyer, K.; Flachbart, K.; Wirth, S.
Detection of Surface States in Quantum Materials ZrTe_{2} and TmB_{4} by Scanning Tunneling Microscopy. *Condens. Matter* **2023**, *8*, 9.
https://doi.org/10.3390/condmat8010009

**AMA Style**

Ale Crivillero MV, Souza JC, Hasse V, Schmidt M, Shitsevalova N, Gabáni S, Siemensmeyer K, Flachbart K, Wirth S.
Detection of Surface States in Quantum Materials ZrTe_{2} and TmB_{4} by Scanning Tunneling Microscopy. *Condensed Matter*. 2023; 8(1):9.
https://doi.org/10.3390/condmat8010009

**Chicago/Turabian Style**

Ale Crivillero, Maria Victoria, Jean C. Souza, Vicky Hasse, Marcus Schmidt, Natalya Shitsevalova, Slavomir Gabáni, Konrad Siemensmeyer, Karol Flachbart, and Steffen Wirth.
2023. "Detection of Surface States in Quantum Materials ZrTe_{2} and TmB_{4} by Scanning Tunneling Microscopy" *Condensed Matter* 8, no. 1: 9.
https://doi.org/10.3390/condmat8010009