Interband Transitions Research Articles

Photoluminescence in Cerium-Doped Fluoride Borate Crystals

Antizeolite fluoride borates LiBa12(BO3)7F4 (LBBF) doped by Ce3+ ions demonstrate photoluminescence (PL) and hold promise for use as phosphors in white light-emitting diodes. In this study, we present the results of modeling the electronic and optical properties of Ce-containing LBBF structures where doping atoms are located at different sites of the host lattice. We also consider the presence of F-centers, which exhibit trap states located within the band gap. We further investigate the nonadiabatic excited state electronic dynamics to elucidate electron-relaxation pathways. The nonadiabatic couplings (NACs) calculations provide transition probabilities facilitated by the nuclear movement. The relaxation rates of electrons and holes are calculated using Redfield’s theory of the formalism of the reduced density matrix (RDM). The PL spectra are calculated using molecular dynamics (MD) sampling and time-integrated methods along the excited state trajectory based on NACs. Mechanisms of PL in LBBF:Ce3+ crystals are interpreted using both computational and experimental observations. This work illustrates the dependence of transition energies, intensities, and relaxation rates of Ce-containing LBBF crystals on a selection of doping sites. In addition to analysis of emission band contributed by cerium, this work allows to identify and reproduce spectral lines hypothetically corresponding to the interband and intraband transitions in F-centers of borate crystals, available in the absence of a metal center.

Abrupt change reflected by the van Hove singularity in the optical spectra of CaMn2P2

The trigonal CaAl2Si2-type structure CaMn2P2 has been reported undergoing an exotic first order phase transition at the critical temperature T K. In this paper, we present the optical spectra for the ab-plane of CaMn2P2 single crystal from 300 K to 10 K for the first time. In the real part of the optical conductivity spectra σ 1(ω), a direct gap could be determined at all temperatures without any Drude term visible, i.e., the sample goes through the first order phase transition from one insulator state to the other insulator state. At higher energy, an asymmetric sharp interband transition peak appears in all σ 1(ω) spectra, which indicates a divergence of the joint density of states. This sharp peak could be well described by the two dimensional van Hove singularity function. In particular, this peak is very sensitive to the first order phase transition, especially the peak position E whose the most prominent blue shift occurs only when the first order transition happens. Our data and analysis reveal that the first order phase transition leads to a weak partial re-normalization of the band structure. Our study will be useful in further investigations about the mechanism of the first order phase transition in the insulator.

Bright Fluorophores in the Second Near-Infrared Window: HgSe/CdSe Quantum Dots

Fluorophores emitting in the NIR-IIb wavelength range (1.5-1.7 μm) show great potential for bioimaging due to their large tissue penetration. However, current fluorophores suffer from poor emission with quantum yields ∼2% in aqueous solvents. In this work, we report the synthesis of HgSe/CdSe core/shell quantum dots (QDs) emitting at 1.7 μm through the interband transition. Growth of a thick shell led to a drastic increase in the photoluminescence quantum yield, with a value of 63% in nonpolar solvents. The quantum yields of our QDs and other reported QDs are explained well by a model of Forster resonance energy transfer to ligands and solvent molecules. The model predicts a quantum yield >12% when these HgSe/CdSe QDs are solubilized in water. Our work demonstrates the importance of a thick type-I shell to obtain bright emission in the NIR-IIb region.

Spectral current density and responsivity scaling for Fourier transform photocurrent spectroscopy.

We propose and experimentally verify a methodology to scale arbitrary units to photocurrent spectral density (A/eV) in Fourier transform Photocurrent (FTPC) spectroscopy. We also propose the FTPC scaling to responsivity (A/W), provided a narrow-band optical power measurement is available. The methodology is based on an interferogram waveform consisting of a constant background and interference contribution. We also formulate conditions that have to be met for correct scaling. We experimentally demonstrate the technique on a calibrated InGaAs diode and weak responsivity, long response time SiC interdigital detector. We identify a series of impurity-band and interband transitions in the SiC detector and slow mid-gap to conduction band transitions.

Coherent control of the orbital occupation driving the insulator-to-metal Mott transition in V2O3

Managing light-matter interactions on timescales faster than the loss of electronic coherence is key for achieving full quantum control of the final products in solid-solid transformations. In this Letter, we demonstrate coherent optical control of the orbital occupation that determines the insulator-to-metal transition in the prototypical Mott insulator ${\mathrm{V}}_{2}{\mathrm{O}}_{3}$. Selective excitation of a specific interband transition with two phase-locked light pulses manipulates the occupation of the correlated bands in a way that depends on the coherent evolution of the photoinduced superposition of states. A comparison between experimental results and numerical solutions of the optical Bloch equations provides an electronic coherence time on the order of 5 fs. Temperature-dependent experiments suggest that the electronic coherence time is enhanced in the vicinity of the insulator-to-metal transition critical temperature, thus highlighting the role of fluctuations in determining the electronic coherence. These results open different routes to selectively switch the functionalities of quantum materials and coherently control solid-solid electronic transformations.

The effects of spin–orbit coupling on optical properties of electronic Lieb lattice in the presence of magnetic field

In this paper, the optical conductivity of a two-dimensional Lieb lattice that is a line-centered square lattice is investigated in the presence of magnetic field and spin–orbit coupling. Specially, we address the frequency dependence of optical conductivity due to spin–orbit interaction. Using Green’s function approach, the behavior of optical conductivity has been obtained in the context of Kane–Mele model Hamiltonian. In the presence of magnetic field at low spin–orbit coupling strength, optical conductivity includes only Drude weight at zero frequency limit while interband transitions of electrons have no contribution to optical conductivity for each gap parameter below normalized value 0.6. However the increase of spin–orbit coupling strength causes to appear finite frequency peak in optical conductivity. Moreover our results show that optical conductivity increases with temperature for each value of spin–orbit coupling and magnetic field. Also we have studied the effects of magnetic field, electron doping and spin–orbit coupling on temperature dependence of optical conductivity of Lieb monolayer.

Formation of emission in diode lasers with evaporation of various impurities on the main semiconductor crystal having affinity to electron

The introduction contains a summary of modern provisions that make it impossible to interpret many phenomena occurring in diode laser systems on the basis of commonly accepted physical conceptions. The work demonstrates their inadequacy. The goal and tasks of studies have been formulated. Analysis of a solid and its internal structure (crystal) is provided. It is demonstrated that interaction of plane surface clusters determines the surface structure of solids, while the interaction between three-dimensional clusters determines the internal structure of solids (crystals). Each atom inside the crystal interacts with the first, second and third coordination layer. The value of conduction band energy is determined by displacement of the ionization boundary. For implementation of diode lasers, the distribution of electrons by Fermi-Dirac energies must have a sufficiently diffused maximum. N-conductivity emerges when ionization of negative ions occurs, the energy of affinity of which is located near the conduction band. Р-conductivity is determined by ionization of negative ions, the energy of affinity of which is located near the valence band. Р-n junction is mostly formed when two-atom molecules enter the band gap. In this case, some of the atoms have an affinity for an electron with the value of such affinity located is near the conduction band, while other atoms have an affinity for an electron near the valence band. Interband transition energy contains three components: 1 – Fermi level position energy; 2 – energy of external applied electrical field, and 3 – induced energy formed by positive charge in the valence band. Generation of laser emission takes place when two-atom molecules are adsorbed on the surface of the semiconductor crystal, in which atoms have an affinity to the electron for some of the atoms near the conduction band and for other atoms near the valence band. Maximum emission intensity occurs when external applied electrical voltage fully compensates the energy of affinity to the electron located near the conduction band.

Silver and Gold Containing Compounds of p-Block Elements As Perspective Materials for UV Plasmonics.

We present a review of phase formation tendencies, methods for preparation and optical properties of alloys and compounds from the binary systems of silver or gold with metals and metalloids from the p-block of the Periodic system of elements. Reference data about the homogeneity regions in the systems of interest, together with information about the crystalline structure of existing indexed compounds in them, is proposed and statistically analyzed. General background for the synthesis of intermetallic alloys and compounds, and the tendencies for their preparation for plasmonic purposes are presented. The high plasma frequency, ωp of p-block metals makes their alloys with silver and gold an interesting object of study, due to the possibility of ωp variation over a wide interval in the ultraviolet (UV) spectral region with a view to finding more efficient materials for excitation of a localized surface plasmon resonance (LSPR) necessary for various applications and techniques operating in this part of the electromagnetic spectrum. Unlike the alloys between the noble metals Cu, Ag, and Au, which form continuous series of solid solutions, different areas can be observed in the phase diagrams of the Ag(Au)-p-block systems, containing solid solutions, intermetallic compounds, and heterogeneous mixtures. The ability to vary the plasma frequency of solid solutions, like the alloys between the noble metals Cu, Ag, and Au, is the reason to pay attention to the compositions of the Ag(Au-p-block systems that fall in these regions of their phase diagrams. The analysis of the published results for complex permittivity shows that the addition of small amounts of conductive p-block elements to noble metals reduces the energy gap for interband transitions and increases their plasmonic activity in the UV spectral range. The article analyzes the relationship between electrical resistivity and LSPR excitation efficiency, which shows that the intermetallic compounds from Ag(Au)-p-block systems with a well-ordered crystalline structure and good conductivity level can be more effective materials for UV plasmonics than the boundary solid solutions. Intermetallic compounds can be easily obtained in the form of bulk samples, thin films, and nanoparticles with controlled size and geometric shape. The spectral dependences of the plasmon efficiency of the intermetallic compounds, determined from their complex permittivity functions, show that they are promising materials for excitation of LSPR in the UV spectral region.

Tuning the Optical Properties of ZnO by Co and Gd Doping for Water Pollutant Elimination

In the present study, pure, Co, Gd, and Co/Gd di-doped ZnO nanoparticles were synthesized via the co-precipitation synthesis route. The prepared samples were characterized through different techniques such as the X-ray diffraction method (XRD), scanning electron microscopy (SEM), UV-Vis spectroscopy, photoluminescence (PL)spectroscopy, and an impedance analyzer and vibrating sample magnetometer (VSM). The XRD pattern shows ZnO’s wurtzite hexagonal crystal structure; moreover, the shifting of characteristic peaks toward the lower angle indicates the inclusion of Co and Co/Gd in the ZnO host lattice. SEM micrographs show various morphologies such as rods, the agglomeration of particles, and spherical nanoparticles. The UV-Vis spectroscopy reveals that the absorption increased in the visible region and there was a substantial redshift for the doped samples. The bandgap decreased from 3.34 to 3.18 eV for the doped samples. The PL spectra show near-edge and inter-band transitions; the origin of inter-band transitions is attributed to the defect states present within the bands. The dielectric constant is strongly frequency dependent and decreases with Co and Co/Gd doping, while the electrical conductivity increases. A VSM study indicates that pure ZnO is diamagnetic, while the Co and Co/Gd doped ZnO nanoparticles showed ferromagnetic behavior. Under UV-visible light irradiation, the Co/Gd-ZnO nanoparticles showed higher photocatalytic activity than the ZnO nanoparticles. The enhanced photocatalytic activity may be attributed to a decreased bandgap with doping.

Intraband Transition of HgTe Nanocrystals for Long-Wave Infrared Detection at 12 μm

The synthesis of n-doped HgTe colloidal quantum dots was optimized to produce samples with a 1Se-1Pe intraband transition in the long-wave infrared (8-12 μm). The spin-orbit splitting of 1Pe states places the 1Se-1Pe1/2 transition around 10 μm. The narrow line width of 130 cm-1 at 300 K is limited by the size distribution. This narrowing leads to an absorption coefficient about 5 times stronger than is possible with the HgTe CQD interband transition at similar energies. From 300 to 80 K, the intraband transition blueshifts by 90 cm-1, while the interband transition redshifts by 350 cm-1. These shifts are assigned to the temperature dependence of the band structure. With ∼2 electrons/dot doping at 80 K, a photoconductive film of 80 nm thickness on a quarter wave reflector substrate showed a detectivity (D*) of ∼107 Jones at 500 Hz in the 8-12 μm range.

Enhancement of Structural, Optical and Photoelectrochemical Properties of n−Cu2O Thin Films with K Ions Doping toward Biosensor and Solar Cell Applications

n-type Cu2O thin films were grown on conductive FTO substrates using a low-cost electrodeposition method. The doping of the n-Cu2O thin films with K ions was well identified using XRD, Raman, SEM, EDX, UV-vis, PL, photocurrent, Mott-Schottky, and EIS measurements. The results of the XRD show the creation of cubic Cu2O polycrystalline and monoclinic CuO, with the crystallite sizes ranging from 55 to 25.2 nm. The Raman analysis confirmed the presence of functional groups corresponding to the Cu2O and CuO in the fabricated samples. Moreover, the samples' crystallinity and morphology change with the doping concentrations which was confirmed by SEM. The PL results show two characteristic emission peaks at 520 and 690 nm which are due to the interband transitions in the Cu2O as well as the oxygen vacancies in the CuO, respectively. Moreover, the PL strength was quenched at higher doping concentrations which reveals that the dopant K limits e-/h+ pairs recombination by trapped electrons and holes. The optical results show that the absorption edge is positioned between 425 and 460 nm. The computed Eg for the undoped and K-doped n-Cu2O was observed to be between 2.39 and 2.21 eV. The photocurrent measurements displayed that the grown thin films have the characteristic behavior of n-type semiconductors. Furthermore, the photocurrent is enhanced by raising the doped concentration, where the maximum value was achieved with 0.1 M of K ions. The Mott-Schottky measurements revealed that the flat band potential and donor density vary with a doping concentration from -0.87 to -0.71 V and 1.3 × 1017 to 3.2 × 1017 cm-3, respectively. EIS shows that the lowest resistivity to charge transfer (Rct) was attained at a 0.1 M concentration of K ions. The outcomes indicate that doping n-Cu2O thin films are an excellent candidate for biosensor and photovoltaic applications.

Multi-step photon upconversion in quantum-dot-based solar cells with a double-heterointerface structure

Photon upconversion (PU) is a process where an electron is excited from the valence band to the conduction band of a wide-gap semiconductor by the sequential absorption of two or more photons via real states. For example, two-step PU can generate additional photocurrent in the so-called intermediate-band solar cells. In this work, we consider two- and three-step processes; we study multi-step PU in a quantum dot (QD)-based single-junction solar cell with a double-heterointerface structure. The solar cell consists of three different absorber layers: Al0.7Ga0.3As, Al0.3Ga0.7As, and GaAs, which form two heterointerfaces. Just beneath each heterointerface, an InAs/GaAs QD layer was inserted. After band-to-band excitation, electrons accumulate at each heterointerface, and then, below-bandgap photons excite a certain fraction of these electrons above the barrier energy. The photoluminescence spectra of the InAs QDs reveal slightly different QD size distributions at the two heterointerfaces. We show that the external quantum efficiency is improved by additional irradiation with below-bandgap infrared photons, which suggests a multi-step PU process that involves the two heterointerfaces. The dependence of the photocurrent on the infrared excitation power density only shows a superlinear behavior when the GaAs layer is excited but the Al0.3Ga0.7As layer is not. These data demonstrate a multi-step PU process that consists of one intraband transition at each of the two heterointerfaces and one interband transition in GaAs.

Nature of excitons in the Ti L and O K edges of x-ray absorption spectra in bulk SrTiO3 from a combined first principles and many-body theory approach

Based on density functional theory calculations, we model the x-ray absorption spectra of the $\mathrm{O} K$ edge and the $\mathrm{Ti} {L}_{2,3}$ edge in bulk ${\mathrm{SrTiO}}_{3}$. Taking into account excitonic effects by solving the Bethe-Salpeter equation is found to be pivotal for obtaining concurrence with the experimental data with respect to the energetic positions and relative intensity of the peaks. Moreover, analysis of the underlying interband transitions in reciprocal space reveals the origin of the prominent peaks and features in the spectra, and provides a deeper understanding of the electronic structure. For example, the characteristic four-peak structure of the $\mathrm{Ti} {L}_{2,3}$ edge results from transitions from $\mathrm{Ti} 2{p}_{3/2}$ states to the unoccupied $\mathrm{Ti} 3d\phantom{\rule{4pt}{0ex}}{t}_{2g}$ (456.1 eV) and $\mathrm{Ti} 3d\phantom{\rule{4pt}{0ex}}{e}_{g}$ states (458.2 eV), followed by transitions from $\mathrm{Ti} 2{p}_{1/2}$ states to $\mathrm{Ti} 3d\phantom{\rule{4pt}{0ex}}{t}_{2g}$ (461.8 eV) and $\mathrm{Ti} 3d\phantom{\rule{4pt}{0ex}}{e}_{g}$ states (463.7 eV). The first bound exciton is strongly localized in real space, and is confined to essentially one unit cell with $3{d}_{xz}$ character near the Ti sites. On the other hand, the first bound exciton of the O K edge is identified as a charge-transfer type with a dominant contribution from the $\mathrm{Ti} 3{d}_{xy}$ states hybridized with O $p$ states. Moreover, the spatial distribution of the exciton wave function shows an intriguing two-dimensional spread in the $x\text{\ensuremath{-}}y$ plane, despite the three-dimensional nature of the material.

Invertible optical nonlinearity in epsilon-near-zero materials

Epsilon-near-zero (ENZ) materials such as indium tin oxide (ITO) have recently emerged as a new platform to enhance optical nonlinearities. Here we report a theoretical and experimental study on the origin of nonlinearities in ITO films that are dominated by intraband and interband transitions. We show that there are two competing factors that jointly contribute to a spectrally invertible nonlinearity of ITO near its ENZ region, i.e., the nonparabolicity of the bands that results in a larger effective mass, and the Fermi energy shift that determines the free carrier density. Our work reveals the relationship between the large nonlinearity and the intrinsic material properties of the ITO films, which will enable design and development of photonic materials and nonlinear devices made of transparent conductive oxides.

Properties of GdSF and phase diagram of the GdF3 - Gd2S3 system

The objectives of this study were to refine the phase diagram of the GdF3-Gd2S3 system and to calculate their liquidus, and to synthesize GdSF and to study their properties. The GdSF compound (ST PbFCl, P4/nmm, a (Å) 3.83006(17), c (Å) 6.8529(3), has an optical band gap for a direct interband transition of 2.56 ​eV and is characterized by a pronounced increase in the Kubelka-Munk function in the region of this transition. Direct optical bandgap of GdSF is measured to be equal to 2.77 ​eV. Two indirect bandgaps are detected to be 1.54 and 2.4 ​eV. Meta-GGA simulations of band structure predicting 1.481 ​eV direct bandgap of GdSF are in good agreement with these features of the experimental absorption spectrum. To explain this complicated case, we argue that formally direct optical transitions to highly dispersive subbands contribute not to direct but to indirect bandgaps measured by Tauc analysis. The GdSF compound melts incongruently with the formation of a melt and γ-Gd2S3 compound at t ​= ​1280 ​± ​2°С, ΔН ​= ​40.6 ​± ​2.8 ​kJ/mol, ΔS ​= ​26.1 ​± ​1.8 ​J/mol∗K. The eutectic has a composition of 13 ​mol.% Gd2S3 (0.74 GdF3 ​+ ​0.26 GdSF), the melting characteristics of the eutectic are 1182 ​± ​2°С, ΔН ​= ​36.2 ​± ​2.5 ​kJ/mol, ΔS ​= ​24.9 ​± ​1.7 ​J/mol∗K. In the system GdF3 - Gd2S3 the balance equations for five phase transformations recorded by the DSC method were compiled. Convergence was achieved in the liquidus of the system constructed according to DSC data and calculated with the use of the Redlich-Kister equation.

Cathodoluminescence Properties of Ni-Decorated Hexagonal Cr Microrods for Magneto-Plasmonic Applications

Multifunctional low-dimensional non-noble metal nanostructures exhibiting a broad range of plasmonic resonances and magnetic properties are expected to be innovative materials suitable for advanced device applications. In this work, we synthesized Ni-nanoparticle-decorated Cr microrods from Cr/Ni thin films driven by solid-state dewetting. The Cr microrod exhibits the phase evolution of the Cr(FCC) to Cr(HCP) with temperature confirmed by X-ray diffraction and high-resolution transmission microscopy. Cathodoluminescence (CL) imaging and spectroscopy of a single Cr microrod reveal plasmonic modes in UV (315 nm), vis (563 nm), and IR (705 nm) ranges. With a dewetting temperature, the red-shifted CL emission peaks indicate tunable plasmonic modes. The origin of the three plasmonic modes can be understood from the orbital electron density of states for d–d intraband and s–d interband transitions. The Ni nanoparticles decorated on Cr microrods also show significant room temperature ferromagnetism. The Ni-nanoparticle-designed Cr microrods may expand the range of magneto-plasmonic materials beyond noble metals. The combination of plasmonic and magnetic properties could facilitate emission-sensitive detection and therapy in plasmonic-based optoelectronic technology.

Near-Field Radiative Heat Transfer between $\\beta-$GeSe monolayers: An ab initio study

ABSTRACT We present a theoretical study of the near-field radiative heat transfer (NFRHT) between two -GeSe monolayers, each at a different temperature. (This is a relevant 2D material with superior electron transport and optical properties compared to black-phosphorus monolayers). The required optical conductivity of the monolayer is calculated using density functional theory including spin-orbit coupling, and using the Perdew-Burke-Erzenhof parametrization. Both the intra and interband transitions are taken into account, as well as the contribution of the optical phonons. This allows us to obtain more realistic predictions of the NFRHT between two monolayers of GeSe. The role of the electron doping concentration and the plasma relaxation frequency is investigated, showing a non-monotonic dependence on the radiative heat transfer with increasing doping, and having an optimal doping where the heat flux is maximize. A strong optical anisotropy in the electric conductivity is obtained from the contribution of both electrons and ions This anisotropy is explored, showing that the relative rotation of two monolayers results in modulation of the NFRHT much larger than previously found for similar 2D materials, like -GeSe. As the angle of rotation between the monolayers increases the total heat transfer decreases. Our analysis demonstrates the relevance of properly taking into account the materialelectronic and ionic contributions.

Perfect excitation and attenuation-free propagation of graphene surface polaritons under optical admittance matching.

Graphene supports both transverse magnetic and electric modes of surface polaritons due to the intraband and interband transition properties of electrical conductivity. Here, we reveal that perfect excitation and attenuation-free propagation of surface polaritons on graphene can be achieved under the condition of optical admittance matching. With both vanished forward and backward far-field radiation, incident photons are fully coupled to surface polaritons. This requires an exact match between the admittance difference of sandwiching media and the conductivity of graphene, resulting in no decay of propagating surface polaritons. The dispersion relation has a completely different line shape for structures that support compared to those that do not support admittance matching. This work promotes complete comprehension of the excitation and propagation behaviors of graphene surface polaritons and may further inspire ideas for research on surface waves on two-dimensional materials.

Quantum Oscillations of Interlayer Conductivity in a Multilayer Topological Insulator

Quantum and difference oscillations of interlayer conductivity in a multilayer system of thin films of topological insulators (TIs) are investigated. Due to the linearity of the carrier spectrum in such a system, new features of quantum oscillations arise. In particular, the frequencies of de Haas–van Alfvén and Shubnikov–de Haas oscillations depend quadratically on the chemical potential, rather than linearly as in systems with parabolic carrier spectrum. For the same reason, the temperature damping factor of oscillations contains the chemical potential. This is due to the nonequidistant character of the Landau levels: the higher the chemical potential, the smaller the distance between Landau levels. However, the beat frequencies, as well as the frequencies of slow oscillations, do not depend on the chemical potential; in this sense, the behavior of these systems is similar to that of conventional non-Dirac systems. Finally, in the Born approximation (in the second order cross-diagram technique), we considered the general case when the interlayer conductivity takes into account both intra- and interband transitions. We have shown that the contribution of intraband transitions is insignificant for the conductivity oscillations in the absence of magnetic impurities. However, in the presence of a Dirac point in the spectrum, a linear (in magnetic field) intraband contribution to conductivity arises from the zero Landau level. At low temperatures, this contribution is exponentially small compared to the intraband contribution and vanishes at zero temperature.

Band Structure Engineering of MXenes for Low‐Loss Visible Epsilon‐Near‐Zero Properties by First‐Principles Calculation

AbstractEpsilon‐near‐zero (ENZ) photonics, which exhibit extraordinary capabilities in terms of controlling light–matter interactions, have been attracting increased interest in recent years. However, several challenges still lie ahead, such as large optical loss and the rarity of ENZ candidates, especially in the visible range. Here, by first‐principles calculations, this work proposes dozens of MXenes with promising plasmonic properties that could be potential ENZ candidates with very low loss in the visible range by band structure engineering. Because of the special electronic structures of these MXenes, they all possess quite large screened plasmonic frequencies: , but less than the interband transition onsets, which cause the ENZ properties in these MXenes to appear in the visible range with very low loss (ε2 less than 0.2) by eliminating the interband transition loss at the ENZ frequencies. Furthermore, it is also demonstrated that the ENZ properties in MXenes, including the ENZ frequency and loss, can be effectively tuned upon surface modifications, such as −Cl and −OH. These outstanding ENZ properties, including tunablity and low‐loss, make these MXenes great for potential applications in ENZ photonics, especially in the visible‐light range.