# Direct observation of highly anisotropic electronic and optical nature in indium telluride

Geoffroy Kremer, Aymen Mahmoudi, Meryem Bouaziz, Cléophanie Brochard-Richard, Lama Khalil, Debora Pierucci, François Bertran, Patrick Le Fèvre, Mathieu G Silly, Julien Chaste, et al.

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Geoffroy Kremer, Aymen Mahmoudi, Meryem Bouaziz, Cléophanie Brochard-Richard, Lama Khalil, et al.. Direct observation of highly anisotropic electronic and optical nature in indium telluride. Physical Review Materials, 2023, 7 (7), pp.074601. 10.1103/physrevmaterials.7.074601. hal-04159938

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Distributed under a Creative Commons Attribution 4.0 International License
Direct observation of highly anisotropic electronic and optical nature in indium telluride

Geoffroy Kremer,¹,² Aymen Mahmoudi,¹ Meryem Bouaziz,¹ Cléophanie Brochard-Richard,¹ Lama Khalil,¹

Debora Pierucci,¹ François Bertran,³ Patrick Le Fèvre,³ Mathieu G. Silly,³ Julien Chaste,¹ Fabrice Oehler,¹ Marco Pala,¹ Federico Bisti,⁴ and Abdelkarim Ouerghi¹,\*

¹Université Paris-Saclay, CNRS, Centre de Nanosciences et de Nanotechnologies, 91120 Palaiseau, Paris, France

²Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, Campus ARTEM, 2 allée André Guinier, BP 50840, 54011 Nancy, France

³Synchrotron SOLEIL, L'Orme des Merisiers, Départementale 128, 91190 Saint-Aubin, France

⁴Dipartimento di Scienze Fisiche e Chimiche, Università dell'Aquila, Via Vetoio, 67100 L'Aquila, Italy

<figure><img src="image_2.png" /></figure>

(Received 15 March 2023; revised 4 June 2023; accepted 14 June 2023; published 11 July 2023)

Metal monochalcogenides (MX, M = Ga, In; X = S, Se, Te) offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. InTe material has a one-dimensional chain structure, from which intriguing properties arise. Precise experimental determination of the electronic structure of InTe is needed for a better understanding of potential properties and device applications. In this study, by combining angle-resolved photoemission spectroscopy and density functional theory calculations, we demonstrate the stability of InTe in the tetragonal crystal structure, with a semiconducting character and an intrinsic *p*-type doping. The valence band maximum results in being located at the high symmetric *M* point with a high elliptical valley, manifesting a large effective mass close to the Fermi level. The longitudinal and transverse effective masses of the *M* valley are measured as 0.2 *m*₀ and 2 *m*₀, respectively. More specifically, we observe that the effective mass of the hole carriers is about ten times larger along the chain direction compared to the perpendicular one. Remarkably, the in-plane anisotropy of effective mass from the experiment and in theoretical calculations are in good agreement. These observations indicate a highly anisotropic character of the electronic band structure, making InTe of interest for electronic and thermoelectric applications.

DOI: 10.1103/PhysRevMaterials.7.074601

I. INTRODUCTION

Low dimensional electronic states bear fascinating emergent physics [1,2]. Recently, the electronic properties of two-dimensional (2D) materials [3], van der Waals (vdW) heterostructures [4], quantum well states confined on the surface/interfaces of semiconductors [5] or oxides [6], and topological surface states of strong topological insulators [7] have been investigated. The low dimension confinement is fascinating because, as what can happen in 1D systems for example, fundamentally important phenomena may emerge, such as the Peierls phase transition [8,9] or topological edge states [10].

In the case of the 2D materials, the anisotropic electronic band structure is typically a consequence of anisotropic crystal structure [11], because in the long-wavelength limit, short-range discreteness of the lattice is averaged out. Such lattice anisotropy can lead to highly anisotropic physical properties such as electric conductivity and phonon group velocity. Meanwhile, anisotropies in physical properties may also lead to device applications which are excessively difficult to obtain using isotropic materials. Among them, anisotropic 2D materials is one kind of system that possess different properties along different directions caused by the intrinsic anisotropic atoms' arrangement, mainly including black phosphorus [12], low-symmetry transition metal dichalcogenides [13–16], and group IV monochalcogenides [17–20]. Recently, a series of

devices has been fabricated based on these anisotropic 2D materials [21]. One of the most pertinent examples in this context is the above mentioned black phosphorus [22,23], a 2D material with a highly anisotropic character and associated signatures in its in-plane thermal, electrical, and thermoelectric transport properties [12,24].

Recently, group-III monochalcogenides have attracted great attention due to their electronical, optical, and thermal properties [25,26]. Their crystal structure consists in covalently bound sheets, stacked vertically through vdW interactions, and with thickness dependent electronic properties [27,28]. In particular, they exhibit band gaps in the 1–3-eV range when the thickness is reduced to a few layers [29], corresponding to the visible light range, showing also high photoresponsivity [30]. Indium selenide (InSe) has first drawn considerable attention due to its high electron mobility and exists in a layered hexagonal structure, with potential application in photodetection and high-density storage [31]. The case of indium telluride (InTe) stands out in its chalcogenide family with a tetragonal crystal structure, mixing weak interactions and covalent bonds in a strongly anisotropic unit cell [32–35]. A recent work has been carried out on the exploration of the electronic properties of InTe hexagonal ultrathin films [36]. It has shown interesting results about the thickness dependence of the band gap in this compound, but in the case of anisotropic tetragonal InTe, the band structure is still not precisely understood and the consequences of unit cell anisotropy on the electronic properties have not been experimentally investigated.

<footnote>*Corresponding author: abdelkarim.ouerghi@c2n.upsaclay.fr</footnote>
In this work, we report the electronic properties of tetrag-
onal InTe, where significant in-plane anisotropies are dis-
covered. Using angle-resolved photoemission spectroscopy
(ARPES), we map the band structure dispersion bringing out
a highly anisotropic behavior of carriers. We determine the
effective masses from the energy and momentum dispersion
relationship at the valence band (VB) extrema. We find a
high anisotropy reaching one order of magnitude between the
effective masses depending on the crystal orientation. Such
result is further supported by the excellent agreement of the
density functional theory (DFT) calculated band structure
with the experimental data. Complementary micro-Raman
spectroscopy analysis is performed to better understand the
structural properties of the crystal, namely by exploring the
vibration frequencies of phonons corresponding to the char-
acteristic vibrational modes of InTe. All data confirm the
existence of relatively flat VB close to the Fermi level with
rather large anisotropic effective masses. This leads to a large
density of state (DOS) close to the Fermi level, that we pro-
pose to interpret as the origin of the peculiar thermoelectric
properties of the material, in relation with its high Seebeck
coefficient [34].

II. METHODS

The Raman spectroscopy measurements were performed
on a Horiba Scientific LabRAM HR at an excitation of λ =
532 nm, in a backscattering geometry in parallel-polarized
configuration, with a 360° rotational sample stage. The spec-
tral resolution is ~0.7 cm⁻¹ for the grating of 1800 grooves
per mm. The spectrometer was calibrated with a pristine
silicon sample. ARPES experiments were performed at the
CASSIOPEE beamline of the SOLEIL synchrotron light
source. The CASSIOPEE beamline is equipped with a Scienta
R4000 hemispherical electron analyzer whose angular accep-
tance is ±15° (Scienta wide angle lens). Commercial InTe
samples from the 2D Semiconductors company were cleaved
in UHV at a base pressure better than 1 × 10⁻¹⁰ mbar. The
experiment was performed at *T* = 50 K and at 80 eV photon
energy if not explicitly specified. The total angle and energy
resolutions were 0.25° and 16 meV, respectively. The incident
photon beam was focused into a 50-μm spot (in diame-
ter) on the sample surface. All ARPES measurements were
performed with a linear horizontal polarization. Core level
photoemission spectroscopy was performed at the TEMPO
beamline of the Synchrotron SOLEIL. The TEMPO beamline
is equipped with a MB scientific A-1 photoelectron analyzer.
The measurements were done at room temperature in a base
pressure of 3 × 10⁻¹⁰ mbar. The spot size of the incident
photon beam was of 300 μm full width at half maximum on
the sample surface. For the curve fitting procedure, a Shirley
background was subtracted to account for the secondary elec-
tron background, and core level peaks were approximated
using the Voight function.

III. RESULTS AND DISCUSSION

Indium telluride crystallizes in a TlSe-type structure [33],
best described by tetragonal space group *I*4/mcm with cell
parameters at 300 K, *a* = *b* = 8.62 Å, and *c* = 7.22 Å. It

can be decomposed as In¹⁺In³⁺Te²⁻, which highlights the
two inequivalent types of In atom in the unit cell. While Te
atoms occupy a single type of crystallographic site (Wyck-
off position 8h), In atoms are distributed over two distinct
crystallographic sites, named hereafter In³⁺ and In¹⁺, respec-
tively [Fig. 1(a)]. The In³⁺ ions are coordinated to the Te²⁻
ions, forming covalently bound tetrahedra, arranged in infinite
chains along the *c* axis. The remaining In¹⁺ ions are placed
regularly between the (InTe₂)⁻ polyhedra and weakly bound
to the Te atoms. These In¹⁺ ions are known to display large
anisotropic thermal displacement parameters [32]. Due to the
weak interactions between (InTe₂)⁻ chains, the crystal tends
to cleave along the (110) planes, along the plane of weakly
bound In¹⁺ ions [34] [Fig. 1(b)].

All InTe single crystals were purchased from 2D Semicon-
ductors (USA). The single-crystalline nature was confirmed
by ARPES [37], which further evidences that the natural
cleavage plane corresponds to the (110) plane (see discussion
below). Micro-Raman and x-ray photoemission spectroscopy
(XPS) measurements confirm the expected stoichiometry of
In and Te in the crystal. A typical room temperature micro-
Raman spectrum is shown in Fig. 1(c) (black line). The E_g and
A_1g peaks are observed at frequencies in agreement with those
previously reported [33,38]: the E_g peak at 48 and 139 cm⁻¹
and the A_1g peak at 127 cm⁻¹. For the A_1g mode, only Te
atoms move in the xy plane, whereas for the E_g mode, In³⁺
and Te atoms vibrate along the xy plane and z direction,
respectively. In both modes, the In¹⁺ atoms do not exhibit any
displacement. Additional peaks are found in low frequency at
46 cm⁻¹ which can be attributed to multiple unit cell shearing
and breathing modes. The emergence of these low frequency
phonon modes indicates that the good crystal quality and the
overall Raman response is consistent with expected I4/mcm
symmetry [33]. We have then studied the anisotropy of InTe
in detail by polarization-dependent Raman spectroscopy at
λ = 532 nm laser excitation (room temperature). The inten-
sity of Raman modes depends on the linear polarization angle
of incident light (θ) in a backscattering Raman configuration.
As shown in Fig. 1(d), where the polar plot of the A_1g Ra-
man line intensity against the in-plane angle θ is shown, the
A_1g (127 cm⁻¹) Raman mode has the largest intensity when
the light polarization is aligned along the *c* axis (90°/270°)
and reaches a minimum value for the perpendicular direc-
tion [1–10] (0°/180°). This behavior is attributed to the
in-plane high optical anisotropy properties of the (110) InTe
surface.

The strong asymmetry of the crystalline structure of InTe
along the *a* and *c* axes is also present in the (110) cleavage
plane [see Fig. 1(b)], and it is expected to also appear in the
electronic properties of the material. To uncover this, we have
studied the electronic anisotropy of the VB as a function of
angle by ARPES combined with DFT calculations [37]. Addi-
tional high-resolution photoemission spectra for In *4d*, and Te
*4d* are recorded using a photon energy of 80 eV (Fig. S1 in the
Supplemental Material [39]). The experimental data points are
displayed in dots and the red solid lines represent the envelope
of the fitted components [40]. The In *4d* spectrum presents
two peaks at a binding energy (BE) of 17.7 and 18.6 eV, which
can be attributed to the In *4d*<sub>5/2</sub> and In *4d*<sub>3/2</sub> [spin-orbit (SO)
splitting of 0.9 eV] [Fig. S1(a)]. Similarly, two components
<figure><img src="image_3.png" /><figcaption>FIG. 1. Crystal structure and structural properties of InTe: (a) Crystal structure of 14/mcm tetragonal InTe crystal, showing to two inequivalent In atoms (In<sup>1+</sup> blue color, In<sup>3+</sup> brown) and the preferential (110) cleavage plane (green color). (b) Local atomic arrangement of the (110) plane, displaying a strong structural anisotropy between the two in-plane directions, with infinite covalently-bounded chains along the *c* axis and weak interaction along [1–10]. (c) Polar-plot dependent Raman spectra of InTe with different in-plane orientation angle theta. For the A<sub>1g</sub> mode, only Te atoms move in the *xy* plane, whereas for the *E*<sub>g</sub> mode, In<sup>3+</sup> and Te atoms vibrate along the *xy* plane and *z* direction, respectively. In both modes, the In<sup>1+</sup> atoms do not exhibit any displacement. (d) Polar plot of the A<sub>1g</sub> Raman line intensity against the in-plane angle theta. Θ = 0 and 90° indicate the *a*- and *c*-axis direction, respectively.</figcaption></figure>

are also present for the Te 4d peak, corresponding to the
Te 4d<sub>5/2</sub> BE = 40.3 eV and 4d<sub>3/2</sub> BE = 41.8 eV with a SO
splitting of 1.5 eV [Fig. S1(b)]. No other components are
detected in the spectra, including oxygen, which demonstrates
the absence of surface oxidation in the probed area. Moreover,
a quantitative analysis, obtained using the intensity of the In
4d and Te 4d peaks, shows a In:Te ratio of about 1, confirming
the monochalcogenide stoichiometry of the InTe crystal.

Electronic band structure features, such as dimensionality
of the band structure and locations of their conduction band
minima (CBM) and valence band maxima (VBM), provide
important insight into the understanding of chalcogenide ma-
terials such as InTe. Before discussing the electronic band
structure measurements, it is of interest to describe the first
Brillouin zone (BZ) of InTe as shown in Fig. 2(a). With a
tetragonal body-centered crystal structure (14/mcm) associ-
ated to inequivalent unit cell parameters *a* and *c*, with *c* < *a*,

the BZ is an elongated dodecahedron, referred as BCT₁ [41].
Due to the body-centered crystal structure in real space, the
closest vectors of the reciprocal space are of type 110, 011,
and 101, akin to body-centered cubic materials. Note that
we maintain the use of a nonprimitive tetragonal unit cell
in the real and reciprocal space. This choice is motivated by
the colinearity between the corresponding real and reciprocal
basis in the nonprimitive tetragonal form, while it is lost
when using the smaller (and less symmetric) primitive cell.
In this notation, the high-symmetry X point lies at ½ (1, 1,
0) in reciprocal space and the ΓX direction simply aligns
with the [1, 1, 0] real space vector. Similarly, the *M*, *Z*, and
*P* coordinates are (1,0,0), (0,0,1), ½ (1, 1, 1) in reciprocal
space, so that Γ*M*, Γ*Z*, and Γ*P* align with [1, 0, 0], [0, 0, 1]
and [1, 1, 1] in real space, respectively. From Fig. 2(a), we see
that the BCT₁ BZ is elongated along Γ*Z* with the existence
of the Z₁MZ₁ segment along the Γ*Z* direction in the *MXP*
<figure><img src="image_4.png" /><figcaption>FIG. 2. Electronic band structure of InTe: (a) Brillouin zone of the body-centered-tetragonal unit cell of InTe. The high-symmetry points are indicated; (b) ARPES 3D mapping in the *MXP* plane; (c) ARPES map of InTe along the *MXM* direction. (d) Comparison of experimental and DFT isoenergetic ARPES maps of InTe at *E*<sub>F</sub> and -0.3 eV.</figcaption></figure>

face (green color), which is the direct consequence of the
shorter *c* axis in real space (*c* < *a*). The shape of the BZ
is particularly relevant to the experimental ARPES parame-
ters, as we want to sample a fraction of momentum space,
large enough to hold the signature of the expected anisotropy
and to support quantitative analysis with theoretical DFT
result.

We now focus our attention on the experimental determi-
nation of the in-plane ARPES data (kₓ, kᵧ) acquired along the
cleaved (110) plane. We particularly focus on the XMP plane
[green color Fig. 2(a)], in which normal is [110] in reciprocal
space and also [110] in real space (using the nonprimitive
orthogonal cell in both spaces). The XMP is particularly
relevant as it should hold the signature of the anisotropy of

the unit cell along *MZ*₁ (i.e., parallel to ΓZ reciprocal space, *c*-axis real space).

In Fig. 2(b), we show the acquired experimental ARPES
data by plotting a series of isoenergetic cuts along the XMP
plane. We confirm that electronic states in the vicinity of
the Fermi level are only found around the *M* points. More-
over, the ARPES measurement shows a single set of two
equivalents *M* points, which indicates that our InTe sample
is fully monocrystalline. In Fig. 2(c), we report the InTe band
structure projection on the surface BZ along the MXM high-
symmetry direction using a photon energy of 80 eV (see the
*k*<sub>*z*</sub> dispersion in Fig. 3). It shows that the VB is characterized
by a downward dispersion in the vicinity of the *M* points.
Figure 2(d) further evidences the strong in-plane anisotropy of
<figure><img src="image_5.png" /><figcaption>FIG. 3. Photon energy dependent ARPES measurements converted to $I(k_z, k_x)$ ARPES map ($E-E_F = -0.5$ eV) for InTe single crystal. The two dashed lines highlight the photon energies corresponding to the $M-X-M$ high-symmetry direction.</figcaption></figure>

the effective hole mass for InTe by showing the elliptical-like shape of the Fermi surface at the *M* point. The comparison between experimental measurements and DFT calculations of the isoenergetic contours in the $\bar{M}XP$ plane [bottom panel in Fig. 2(d)] confirms the presence of states only around the $\bar{M}$ point in the vicinity of the Fermi level. This is in good agreement with our experimental data and further confirms the natural (110) cleavage plane of InTe [Fig. 1(b)], which sets the experimental axis of our ARPES data, with the $\bar{X}MP$ plane being sampled in-plane along ($k_x, k_y$) and $k_y$ aligning with $\Gamma Z$ and the *c* axis of the tetragonal unit cell.

In order to gain more insight on the electronic structure of InTe, we performed electronic band structure calculations using both Perdew-Burke-Ernzerhof (PBE) [42] and Heyd-Scuseria-Ernzerhof (HSE) hybrid functionals [43]. Figure 4(a) shows the measured band structure in the vicinity of the $\bar{M}XM$ direction at large scale. The top of the VB at the *M* point is mostly formed by *p* orbitals of Te and *s* orbitals

of In, respectively, while the conduction band (CB) is mostly composed by *s* orbitals of Te and *p* orbitals of In, as can be seen from the orbital projected LDOS plotted in Figs. S2 and S3 [39]. The electronic structure from the Fermi level down to 3 eV binding energy (BE) is in good agreement with our electronic structure calculations [Figs. 4(b) and 4(c)], although the energy separation between the top of the VB at *M* and *X* is slightly underestimated with PBE [Fig. 4(b)]. Specifically, we demonstrate the agreement between the ARPES results and DFT calculations. In both theory and experiments the VB maximum at the *M* point is located at lower BE than at the *X* point. The energy separation between the *M* and *X* is comparable: 1 eV in experimental data [Fig. 4(b)], 1 eV in PBE, and 1.1 eV in HeydScuseriaErnzerhof (HSE) [Figure 4(c)]. Finally, it is worthwhile to mention that a local CBM is also situated at the *M* point for both the PBE and HSE functionals. However, the energy separation at this high-symmetry point is substantially underestimated in PBE. The value obtained with the hybrid functional is more accurate and is expected to underestimate the quasiparticle band gap by no more than 10%, as observed in other members of the indium monochalcogen and $MX_2$ family [44].

In order to evaluate the strong in-plane anisotropy of the VB dispersion near the *M* point, we perform an analysis of the curvature of the VBs from the ARPES measurements in two separate directions. We present in Figs. 5(b) and 5(c) the electronic band structure along the two perpendicular directions of InTe around the *M* point. A parabolic fit is employed to describe the local curvature of the VB maximum at *M*, but it should be remarked that the curves present a significant non-parabolic character, leading to a degree of incertitude in the extracted value of the effective mass. The adopted quadratic function is indicated by a red-colored line in Figs. 5(b) and 5(c). We have determined the effective mass of the hole close to the *M* point of the BZ along the $XMX$ and $ZMZ$ high-symmetry directions. The experimental dispersion has been fitted with a parabolic model $E(k) = E + \hbar k^2/2m^*$ where $m^*$ is the effective electron mass and $\hbar$ is the reduced Planck. We thus derive two experimental values of 0.2 $m_0$ and 2 $m_0$ (where $m_0$ is the free electron mass) at the *M* point along $MX$ and $MZ$.

<figure><img src="image_6.png" /><figcaption>FIG. 4. ARPES data of InTe measured in the vicinity of the $\bar{M}-\bar{X}-\bar{M}$ high-symmetry direction compared with theoretical electronic band structure: (a) ARPES map of InTe along the $MXM$ high-symmetry directions ($T = 50$ K and $h\nu = 55$ eV). (b),(c) Comparison between ARPES map and DFT calculations (PBE and HSE, respectively). The calculation was performed by considering an offset of 10% with respect to the $MXM$ high-symmetry direction. For this photon energy, VBM is located at the *M* point.</figcaption></figure>
<figure><img src="image_7.png" /><figcaption>FIG. 5. Anisotropic effective hole masses of InTe near the valence band maximum: (a) Isoenergetic ARPES maps of InTe at -0.5 eV below $E_F$. ARPES cut data along the in-plane momentum defined by the angle $\theta$ [see colored lines in Fig. 4(a) for definition] for InTe. All the data sets are centered around the $M$ point at which VBM is located; (b),(c) ARPES cuts along and perpendicular to the MXM direction. The red lines indicate a quadratic function fitting the dispersions of the top-most bands. (d) Comparison of experimental and DFT polar plot of the effective mass against the in-plane angle theta. $\Theta = 0$ and $90^\circ$ indicates the a- and c-axis direction, respectively.</figcaption></figure>

($MZ_1$), respectively. These values agree very well with the PBE and HSE calculations, suggesting that many body effects are not important close to the top of the VB at $M$. One can notice that this mass is close to $m_0$ which implies that the InTe band is poorly dispersive. This feature leads to the appearance of a large DOS near the top of the VB of InTe, as observed by DFT calculations. The emergence of the high DOS can enhance thermoelectric transport properties such as the same phenomena observed in the Si doped InSe [45].

The in-plane anisotropic character of VB dispersion is analyzed in more detail in Fig. 5(d). There we plot in polar coordinates the value of the relative effective mass $m/m_0$ computed from the parabolic fit of the ARPES data (red triangle) and DFT (blue circle) against the in-plane angle $\theta$, with $\theta = 90^\circ$ along the $\Gamma Z$ direction (real space c axis) and $\theta = 0^\circ$ along the MXM high-symmetry direction. Note that the $\theta$ angle, defined here in reciprocal space, is equivalent to the polar coordinate used for the anisotropic Raman analysis in real space [Fig. 1(d)]. The plot clearly shows a twofold symmetry and the strong in-plane anisotropy of the effective hole mass for InTe. We retrieve the specific values obtained previously for the high-symmetry lines at $\theta = 0/180^\circ$ [$MX$] and $\theta = 90/270^\circ$ [$MZ$], respectively. Due to the nonparabolic dispersion of the VB, our experimental determination of the effective mass is sensitive to the fitting range. Here, the

(one dimensional) fitting range is fixed to 1/8 of the $M-X$ length in reciprocal space. If this fitting range is doubled, the experimental effective masses may change up to 10%. Comparing our experimental effective mass to first principles calculations, we obtain an overall good agreement, with $2m_0$ along the infinite $(\text{InTe}_2)^-$ chains (c axis, $\Gamma Z$ direction) and $0.2m_0$ perpendicular to it. As electron-electron and electron-phonon interactions, as well as atomic spin-orbit coupling of InTe, are not considered in our DFT calculations, local discrepancies can exist between the experimental and theoretical band structures and effective masses.

In summary, we have presented an exhaustive study of the electronic band structure of InTe cleaved along the (110) surface, combining spectroscopic tools and theoretical investigations. Using polarization-dependent Raman spectroscopy and ARPES, we characterized the anisotropic character of tetragonal InTe and we relate each parameter to the crystal structure and local orientation. We have found that InTe is stable in the tetragonal phase and is a 0.4 eV band gap semiconductor with high p doping. We systematically investigated in-plane directional dependence of the effective hole mass of the VB of InTe in the vicinity of the Fermi level. The hole effective mass of the $M$ valley exhibits a strong anisotropy, about ten times heavier along the $(\text{InTe}_2)^-$ chains, c axis, than along the direction perpendicular to it. The in-plane
anisotropy of the hole effective masses in InTe is larger than that in black phosphorus which also shows anisotropic optical and electronic properties. In this context, InTe can be considered a highly anisotropic material in terms of the low energy hole carrier dynamics, which makes this material a promising thermoelectric candidate for highly anisotropic semiconducting electronics. The highly anisotropic character of the hole carriers as well as possibility of the electron-electron and electron-phonon interactions may lead to collective electron order such as charge density waves, which has already been observed for doped samples and that could be explored with ARPES in the future.

The data sets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

ACKNOWLEDGMENTS

We acknowledge the financial support by MagicValley (Grant No. ANR-18-CE24-0007), Graskop (Grant No. ANR-19-CE09-0026), 2D-on-Demand (Grant No. ANR-20-CE09-0026), and MixDferro (Grant No. ANR-21-CE09-0029), as well as the French technological network RENATECH.
The authors declare no competing interests.

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