# Alex Delhomme's research while affiliated with Université Grenoble Alpes and other places

## Publications (27)

Article
Full-text available
Magnetic layered materials have emerged recently as promising systems to introduce magnetism in structures based on two-dimensional (2D) materials and to investigate exotic magnetic ground states in the 2D limit. In this work, we apply high hydrostatic pressures up to P ≈ 8.7 GPa to the bulk layered antiferromagnet FePS3 to tune the collective latt...
Preprint
Magnetic layered materials have emerged recently as promising systems to introduce magnetism in structures based on two-dimensional (2D) materials and to investigate exotic magnetic ground states in the 2D limit. In this work, we apply high hydrostatic pressures up to P = 8.7 GPa to the bulk layered antiferromagnet FePS$_3$ to tune the collective l...
Preprint
Full-text available
Single spin defects in 2D transition-metal dichalcogenides are natural spin-photon interfaces for quantum applications. Here we report high-field magneto-photoluminescence spectroscopy from three emission lines (Q1, Q2 and Q*) of He-ion induced sulfur vacancies in monolayer $\text{MoS}_2$. Analysis of the asymmetric PL lineshapes in combination wit...
Thesis
Semiconductor transition metal dichalcogenides (s-TMDs) are a group of materials showing unique optical properties making them good candidates for opto-electronic applications at the nanoscale. While these compounds have been studied for more than half a century already, they have gained interest during the intense stimulation of scientific researc...
Preprint
Full-text available
We present an experimental set-up developed to perform optical spectroscopy experiments (Raman scattering and photoluminescence measurements) with a micrometer spatial resolution, in an extreme environment of low temperature, high magnetic field and high pressure. This unique experimental setup, to the best of our knowledge, allows us to explore de...
Article
Full-text available
We present an experimental setup developed to perform optical spectroscopy experiments (Raman scattering and photoluminescence measurements) with a micrometer spatial resolution in an extreme environment of low temperature, high magnetic field, and high pressure. This unique experimental setup, to the best of our knowledge, allows us to deeply expl...
Article
The hybridization of magnons (spin waves) with phonons, if sufficiently strong and comprising of long wavelength excitations, may offer a new playground when manipulating the magnetically ordered systems with light. Applying a magnetic field to a quasi-two-dimensional antiferromagnet, FePS3, we tune the magnon-gap excitation to coincide with the in...
Preprint
Full-text available
We report magneto-photoluminescence spectroscopy of gated MoS$_2$ monolayers in high magnetic fields to 28 T. At B = 0T and electron density $n_s\sim 10^{12}cm^-2$, we observe three trion resonances that cannot be explained within a single-particle picture. Employing ab initio calculations that take into account three-particle correlation effects a...
Preprint
Full-text available
The hybridization of magnons (spin waves) with phonons, if sufficiently strong and comprising long wavelength excitations, may offer a new playground when manipulating the magnetically ordered systems with light. Applying a magnetic field to a quasi-2D antiferromagnet, FePS3, we tune the magnon-gap excitation towards coincidence with the initially...
Article
Full-text available
Strong Coulomb correlations together with multi-valley electronic bands in the presence of spin-orbit interaction are at the heart of studies of the rich physics of excitons in monolayers of transition metal dichalcogenides (TMD). Those archetypes of two-dimensional systems promise a design of new optoelectronic devices. In intrinsic TMD monolayers...
Article
Full-text available
Materials combining semiconductor functionalities with spin control are desired for the advancement of quantum technologies. Here, we study the magneto-optical properties of novel paramagnetic Ruddlesden-Popper hybrid perovskites Mn:(PEA) 2 PbI 4 (PEA = phenethylammonium) and report magnetically brightened excitonic luminescence with strong circula...
Preprint
Full-text available
Strong Coulomb correlations together with multi-valley electronic bands in the presence of spin-orbit interaction and possible new optoelectronic applications are at the heart of studies of the rich physics of excitons in semiconductor structures made of monolayers of transition metal dichalcogenides (TMD). In intrinsic TMD monolayers the basic, in...
Preprint
Full-text available
Materials combining the optoelectronic functionalities of semiconductors with control of the spin degree of freedom are highly sought after for the advancement of quantum technology devices. Here, we report the paramagnetic Ruddlesden-Popper hybrid perovskite Mn:(PEA)2PbI4 (PEA = phenethylammonium) in which the interaction of isolated Mn2+ ions wit...
Article
Full-text available
Excitons with binding energies of a few hundreds of meV control the optical properties of transition metal dichalcogenide monolayers. Knowledge of the fine structure of these excitons is therefore essential to understand the optoelectronic properties of these 2D materials. Here we measure the exciton fine structure of MoS2 and MoSe2 monolayers enca...
Preprint
Full-text available
We explore the many-body interaction of neutral, positively and negatively charged electron-hole pairs in a MoS$_2$ monolayer with the distinct spin and valley textures of resident charges via density dependent high field magneto-optical spectroscopy. For the neutral exciton we unexpectedly observe nonlinear valley Zeeman effects, which we explain...
Article
Full-text available
Optical selection rules in monolayers of transition metal dichalcogenides and of their heterostructures are determined by the conservation of the z-component of the total angular momentum - J Z = L Z +S Z - associated with the C3 rotational lattice symmetry which assumes half integer values corresponding, modulo 3, to distinct states. Here we show,...
Preprint
We report experimental and theoretical studies on the magnetoelastic interactions in MnPS$_3$. Raman scattering response measured as a function of temperature shows a blue shift of the Raman active modes at 120.2 and 155.1 cm$^{-1}$, when the temperature is raised across the antiferromagnetic-paramagnetic transition. Density functional theory (DFT)...
Preprint
Identifying quantum numbers to label elementary excitations is essential for the correct description of light-matter interaction in solids. In monolayer semiconducting transition metal dichalcogenides (TMDs) such as MoSe$_2$ or WSe$_2$, most optoelectronic phenomena are described well by labelling electron and hole states with the spin projection a...
Preprint
Full-text available
Excitons with binding energies of a few hundreds of meV control the optical properties of transition metal dichalcogenide monolayers. Knowledge of the fine structure of these excitons is therefore essential to understand the optoelectronic properties of these 2D materials. Here we measure the exciton fine structure of MoS2 and MoSe2 monolayers enca...
Article
The results of magneto-optical spectroscopy investigations of excitons in a CVD grown monolayer of WSe2 encapsulated in hexagonal boron nitride are presented. The emission linewidth for the 1s state is of 4.7 meV, close to the narrowest emissions observed in monolayers exfoliated from bulk material. The 2s excitonic state is also observed at higher...
Preprint
Full-text available
The results of magneto-optical spectroscopy investigations of excitons in a CVD grown monolayer of WSe2 encapsulated in hexagonal boron nitride are presented. The emission linewidth for the 1s state is of 4:7 meV, close to the narrowest emissions observed in monolayers exfoliated from bulk material. The 2s excitonic state is also observed at higher...

## Citations

... [9][10][11][12][13][14][15]. Moreover, the rich landscape of bright, dark and excited trion states has been observed in optical absorption and emission spectra [16][17][18][19][20][21][22][23][24][25] and partially understood with different theoretical approaches [15,[24][25][26][27]. Other studies have explored the dynamics of trion formation [28], recombination [29], and valley depolarization [16,30]. ...
... The DAC is placed on piezo motors allowing for spatial displacements in three directions with sub-micrometer resolution. For magneto-optical measurements, we use a home-made optical experimental setup which detailed description can be found in Ref. [38]. It is based on free-beam optics with a 12 mm working distance objective (numerical aperture NA= 0.35) to excite the sample and to collect the scattered signals. ...
... None of those features has yet been detected in the bulk crystal. Infrared (IR) spectroscopy data complementary to Raman scattering data are also lacking 20 . In the case of VI3, such a lack of information caused a misinterpretation of the crystallographic phases and phase transitions 19 . ...
... Valley Zeeman splitting of these excitonic complexes has been reported under application of strong out-of-plane magnetic fields (B fields) 3,6,10 . However, translating the relatively large Zeeman splitting of a purely matter-bound excitation into a photonic mode splitting remains a fundamental challenge, not only in opto-valleytronics 11 , but also in topological photonics. ...
... The lowest conduction bands, CB ± , and highest valence bands, VB ± , are indicated in figure 1(b), with the subindex + or − referring to the energetic band ordering. These are the important energy bands that contribute to the formation of the A and B ('bright') excitons, with in-plane optical selection rules, and of the D ('dark') exciton, with out-of-plane optical selection rule [14,15,33,34,36,[101][102][103]. The relevant low energy bands that contribute to the formation of the A, B and D excitons are sketched in figure 2. Regarding spin, the values of S z are rather homogeneous for CB ± and VB ± along the high-symmetry k-path, i.e., the bands are highly spin polarized with |S z | ∼ 1. ...
... In addition to the monotonic PL red-shift of the primary peak (center energy 2.348 eV at 4 K, Fig. S11), a second, low-energy peak emerges below ~140 K, which is consistent with reports of a dark exciton (DX, center energy 2.323 eV at 4 K, Fig. 3a and Fig. S11) shown to increase in PL intensity in the presence of an external magnetic field. [78][79][80] Emission without a magnetic field has also been observed due to spin-orbit coupling and dipole mixing with the bright exciton (X). 79,80 Though the films posses a high degree of crystallinity ( Fig. S5), we are unable to resolve the four states reported within the fine structure for the bright and dark excitons due to PL broadening resulting from disorder of the polycrystalline thin film. ...
... In the case of darkish MLs, that transition is optically inactive (dark). MoSe 2 and MoTe 2 MLs are bright, while MoS 2 , WS 2 , and WSe 2 MLs are darkish (see Refs. [14][15][16]. The determination of bright or darkish character of the excitonic ground state of alloy MLs is still missing. ...
... Chiral phonons were studied in many two dimensional (2D) lattices, e.g., honeycomb lattice [1,2], kagome lattice [3], or moiré superlattices [4]. Recently, chiral phonons were also reported in many three dimensional (3D) materials, e.g.: transition metal dichalcogenides [5][6][7][8] and their heterostructures [9][10][11], pervoskites [12][13][14][15], graphene/hexagonal boron nitride heterostructure [16], 2D magnets (CrBr 3 [17] or Fe 3 GeTe 2 [18]), cuprates [19], CoSn-like systems [20], ternary YAlSi compound [21], chiral systems (ABi-like compounds [22], α-HgS [23] or SiO 4 [24]), and magnetic topological insulators T Bi 2 Te 4 [25]. Due to their extraordinary properties (e.g., realization of the phonon Hall effect [26][27][28][29][30][31][32][33]), it has attracted a lot of theoretical and experimental attentions. ...
... Third, the relatively low AFM ordering temperature (T N = 78 K) allows thermal versus non-thermal induced effects to be readily distinguished. Fourth, the timescale for spin dynamics, which may be induced by light directly via magneto-optical effects or indirectly via magneto-elastic coupling [26], is limited to around 5 ps based on the magnetic exchange interaction strength [27]. Therefore, any dynamics occurring on the timescale of a femtosecond driving pulse can be confined to the charge sector. ...
... All of those experiments confirmed that the spectrum of s-like states deviates strongly from the 2D hydrogen-like series. Further experiments in magnetic fields reached up to 5s excited states [51][52][53][54][55], addressing also the complicated problem of the diamagnetic shifts of exciton lines resulting from three contributions (see Figure 1), as discussed theoretically in one of our other works [56]. The exciton series consists not only of bright s-series but also of two types of dark states-spin-forbidden and excited excitons states with symmetry different from 's'. ...