arXiv subjects

D. Malterre

Publications and source records attributed to D. Malterre.

12 recordsLinked to original sources

arXiv2026

Kondo scaling of $4f$-electron states and the Kondo singlet breakdown in heavy fermions

The low-energy spin- and charge-sensitive thermodynamic properties of a broad range of strongly correlated 4f-electron systems follow Kondo scaling, with a characteristic Kondo temperature, $T_K$. While the theory is known for thermodynamic properties and high-energy spectroscopies of Kondo materials, the surface sensitivity of electron spectroscopy limits the extent to which Kondo scaling can be quantitatively verified. In this study, bulk-sensitive photon-in photon-out temperature-dependent resonant inelastic X-ray scattering (RIXS), in combination with single-impurity Anderson model (SIAM) calculations, is used to provide quantitative evidence of low- and high-energy Kondo scaling in CeSi$_2$. RIXS Ce M$_5$-edge spectra show a clear decrease in the occupancy of the $f^0$ state as temperature increases accompanied by an increase of the spectral weight of the $f^1\underline L^1$ state, in good agreement with the SIAM calculations. The results demonstrate the breakdown of the Kondo singlet state, coupled with thermal occupation of the low-lying first-excited magnetic states. The RIXS data reveal a temperature evolution of the $f^n$ spectral weights, which is in stark contrast to that extracted from photoemission and inverse photoemission spectroscopies. This study provides an accurate spectroscopic method to determine the Kondo energy $k_B$$T_K$ that is consistent with thermodynamic measurements, and highlights soft X-ray RIXS as a quantitative bulk probe of low- and high-energy-scale hybridization effects in strongly correlated materials.

cond-mat.str-el↗

arXiv2026

Anomalous pressure dependence of the bulk modulus and Yb valence in cubic YbPd

We investigate the Yb valence instabilities in the strongly correlated YbPd compound using resonant X-ray emission spectroscopy as a function of pressure across the charge-order (CO) transition. At a low temperature (T = 30 K) in the CO phase, the Yb $4f$ valence remains nearly constant up to a pressure P$_L$ = 1.5 $\pm {0.2}$ GPa, and then increases gradually at higher pressures. In contrast, at room temperature in the normal phase, an anomalous decrease of the Yb $4f$ valence is observed, without any accompanying structural phase transition. This behavior is corroborated by a systematic pressure-dependent decrease of the unit-cell volume. Based on a Birch-Murnaghan analysis, the compressibility indicates hardening of the lattice with applied pressure up to a distinct kink seen at P$_K$ = 1.6 $\pm {0.2}$ GPa. In contrast, for P $>$ P$_K$, the Yb $4f$ valence saturates and the compressibility reveals a counterintuitive pressure-induced softening. The results show a minimum in the compressibility of YbPd (with $f^{0}$-$f^{1}$ hole-type mixed-valence), reminiscent of the maximum in compressibility seen in the $γ$-$α$ first-order isostructural phase transition in cerium (with $f^{0}$-$f^{1}$ electron-type mixed-valence).

cond-mat.str-el↗

arXiv2023

Oxygen on-site Coulomb energy in Pr$_{1.3-x}$La$_{0.7}$Ce$_x$CuO$_{4}$ and Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ and its relation with Heisenberg exchange

We study the electronic structure of electron-doped Pr$_{1.3-x}$La$_{0.7}$Ce$_{x}$CuO$_{4}$ (PLCCO ; $T_{c}$ = 27 K, x = 0.1) and hole-doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (Bi2212 ; $T_{c}$ = 90 K) cuprate superconductors using x-ray absorption spectroscopy (XAS) and resonant photoemission spectroscopy (Res-PES). From Res-PES across the O K-edge and Cu L-edge, we identify the O 2p and Cu 3d partial density of states (PDOS) and their correlation satellites which originate in two-hole Auger final states. Using the Cini-Sawatzky method, analysis of the experimental O 2p PDOS shows an oxygen on-site Coulomb energy for PLCCO to be $U_{p}$ = 3.3$\pm$0.5 eV and for Bi2212, $U_{p}$ = 5.6$\pm$0.5 eV, while the copper on-site Coulomb correlation energy, $U_{d}$ = 6.5$\pm$0.5 eV for Bi2212. The expression for the Heisenberg exchange interaction $J$ in terms of the electronic parameters $U_{d}$, $U_{p}$, charge-transfer energy $Δ$ and Cu-O hopping $t_{pd}$ obtained from a simple Cu$_2$O cluster model is used to carry out an optimization analysis consistent with $J$ known from scattering experiments. The analysis also provides the effective one band on-site Coulomb correlation energy $\tilde{U}$ and the effective hopping $\tilde{t}$. PLCCO and Bi2212 are shown to exhibit very similar values of $\tilde{U}$/$\tilde{t}$ $\sim$9-10, confirming the strongly correlated nature of the singlet ground state in the effective one-band model for both the materials.

cond-mat.str-el↗

arXiv2023

Connecting the one-band and three-band Hubbard models of cuprates via spectroscopy and scattering experiments

The one-band and three-band Hubbard models which describe the electronic structure of cuprates indicate very different values of effective electronic parameters, such as the on-site Coulomb energy and the hybridization strength. In contrast, a comparison of electronic parameters of several cuprates with corresponding values from spectroscopy and scattering experiments indicates similar values in the three-band model and cluster model calculations used to simulate experimental results. The Heisenberg exchange coupling $J$ obtained by a downfolding method in terms of the three band parameters is used to carry out an optimization analysis consistent with $J$ from neutron scattering experiments for a series of cuprates. In addition, the effective one-band parameters $\tilde{U}$ and $\tilde{t}$ are described using the three band parameters, thus revealing the hidden equivalence of the one-band and three-band models. The ground-state singlet weights obtained from an exact diagonalization elucidates the role of Zhang-Rice singlets in the equivalence. The results provide a consistent method to connect electronic parameters obtained from spectroscopy and the three-band model with values of $J$ obtained from scattering experiments, band dispersion measurements and the effective one-band Hubbard model.

cond-mat.str-el↗

arXiv2019

Electronic band structure of ultimately thin silicon oxide on Ru(0001)

Silicon oxide can be formed in a crystalline form, when prepared on a metallic substrate. It is a candidate support catalyst and possibly the ultimately-thin version of a dielectric host material for two-dimensional materials (2D) and heterostructures. We determine the atomic structure and chemical bonding of the ultimately thin version of the oxide, epitaxially grown on Ru(0001). In particular, we establish the existence of two sub-lattices defined by metal-oxygen-silicon bridges involving inequivalent substrate sites. We further discover four electronic bands below Fermi level, at high binding energies, two of them forming a Dirac cone at K point, and two others forming semi-flat bands. While the latter two correspond to hybridized states between the oxide and the metal, the former relate to the topmost silicon-oxygen plane, which is not directly coupled to the substrate. Our analysis is based on high resolution X-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, scanning tunneling microscopy, and density functional theory calculations.

cond-mat.mtrl-sci↗

arXiv2018

Band structure and Fermi surfaces of the reentrant ferromagnetic superconductor Eu(Fe0.86Ir0.14)2As2

The electronic structure of the reentrant superconductor Eu(Fe$_{0.86}$Ir$_{0.14}$)$_{2}$As$_{2}$ (T$_c$ = 22 K) with coexisting ferromagnetic order (T$_M$ = 18 K) is investigated using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling spectroscopy (STS). We study the in-plane and out-of-plane band dispersions and Fermi surface (FS) of Eu(Fe$_{0.86}$Ir$_{0.14}$)$_{2}$As$_{2}$. The near E$_F$ Fe 3d-derived band dispersions near the $Γ$ and X high-symmetry points show changes due to Ir substitution, but the FS topology is preserved. From momentum dependent measurements of the superconducting gap measured at T = 5 K, we estimate an essentially isotropic s-wave gap ($Δ\sim5.25\pm 0.25$ meV), indicative of strong-coupling superconductivity with 2$Δ$/k$_{B}$T$_{c}\simeq$ 5.8. The gap gets closed at temperatures T $\geq$ 10 K, and this is attributed to the resistive phase which sets in at T$_M$ = 18 K due to the Eu$^{2+}$-derived magnetic order. The modifications of the FS with Ir substitution clearly indicates an effective hole doping with respect to the parent compound.

cond-mat.mtrl-sci↗

arXiv2017

Evidence for weakly correlated oxygen holes in the highest-T$_{c}$ cuprate superconductor HgBa$_2$Ca$_2$Cu$_3$O$_{8+δ}$

We study the electronic structure of HgBa$_2$Ca$_2$Cu$_3$O$_{8+δ}$ (Hg1223 ; T$_{c}$ = 134 K) using photoemission spectroscopy (PES) and x-ray absorption spectroscopy (XAS). Resonant valence band PES across the O K-edge and Cu L-edge identify correlation satellites originating in O 2p and Cu 3d two-hole final states, respectively. Analyses using the experimental O 2p and Cu 3d partial density of states show quantitatively different on-site Coulomb energy for the Cu-site (U$_{dd}$ = 6.5$\pm$0.5 eV) and O-site (U$_{pp}$ = 1.0$\pm$0.5 eV). Cu$_{2}$O$_{7}$-cluster calculations with non-local screening explain the Cu 2p core level PES and Cu L-edge XAS spectra, confirm the U$_{dd}$ and U$_{pp}$ values, and provide evidence for the Zhang-Rice singlet state in Hg1223. In contrast to other hole-doped cuprates and 3d-transition metal oxides, the present results indicate weakly correlated oxygen holes in Hg1223.

cond-mat.str-el↗

arXiv2015

Quasi one-Dimensional Band Dispersion and Metallization In long Range Ordered Polymeric wires

We study the electronic structure of an ordered array of poly(para-phenylene) chains produced by surface-catalyzed dehalogenative polymerization of 1,4-dibromobenzene on copper (110). The quantization of unoccupied molecular states is measured as a function of oligomer length by scanning tunneling spectroscopy, with Fermi level crossings observed for chains longer than ten phenyl rings. Angle-resolved photoelectron spectroscopy reveals a graphene-like quasi one-dimensional valence band as well as a direct gap of 1.15 eV, as the conduction band is partially filled through adsorption on the surface. Tight-binding modelling and ab initio density functional theory calculations lead to a full description of the organic band-structure, including the k dispersion, the gap size and electron charge transfer mechanisms which drive the system into metallic behaviour. Therefore the entire band structure of a carbon-based conducting wire has been fully determined. This may be taken as a fingerprint of π-conjugation of surface organic frameworks.

cond-mat.mes-hall↗

arXiv2014

Atomic and Electronic Structure of a Rashba $p$-$n$ Junction at the BiTeI Surface

The non-centrosymmetric semiconductor BiTeI exhibits two distinct surface terminations that support spin-split Rashba surface states. Their ambipolarity can be exploited for creating spin-polarized $p$-$n$ junctions at the boundaries between domains with different surface terminations. We use scanning tunneling microscopy/spectroscopy (STM/STS) to locate such junctions and investigate their atomic and electronic properties. The Te- and I-terminated surfaces are identified owing to their distinct chemical reactivity, and an apparent height mismatch of electronic origin. The Rashba surface states are revealed in the STS spectra by the onset of a van Hove singularity at the band edge. Eventually, an electronic depletion is found on interfacial Te atoms, consistent with the formation of a space charge area in typical $p$-$n$ junctions.

cond-mat.mes-hall↗

arXiv2009

Surface state bi-polarons formation on a triangular lattice in the sp-type alkali/Si(111) Mott insulator

We report on new LEED, STM and ARPES studies of alkali/Si(111) previously established as having a Mott insulating ground state at surface. The observation of a strong temperature dependent Franck-Condon broadening of the surface band together with the novel $\sqrt{3}\times\sqrt{3}\to2(\sqrt{3}\times\sqrt{3})$ charge and lattice ordering below 270 K evidence a surface charge density wave (SCDW) in the strong e-ph coupling limit ($g\approx8$). Both the adiabatic ratio $\hbarω_0/t\approx0.8$ and the effective pairing energy $V_{eff}=U-2g\hbarω_0\approx-800$ $meV$ are consistent with the possible formation of a bi-polaronic insulating phase consisting of alternating doubly-occupied/unoccupied dangling bonds as expected in the Holstein-Hubbard model.

cond-mat.str-el↗

arXiv2006

Observation of a Mott insulating ground state for Sn/Ge(111) at low temperature

We report an investigation on the properties of 0.33 ML of Sn on Ge(111) at temperatures down to 5 K. Low-energy electron diffraction and scanning tunneling microscopy show that the (3x3) phase formed at 200 K, reverts to a new (root-3xroot-3)R30 phase below 30 K. The vertical distortion characteristic of the (3x3) phase is lost across the phase transition. Angle-resolved photoemission experiments show that concomitantly with the structural phase transition, a metal-insulator phase transition takes place. In agreement with theoretical predictions, the (root-3xroot-3)R30 ground state is interpreted as the experimental realization of a Mott insulator for a narrow half-filled band in a two-dimensional triangular lattice.

cond-mat.mtrl-sci↗

arXiv2002

Anomalous spectral weight in photoemission spectra of the hole doped Haldane chain Y2-xSrxBaNiO5

In this paper, we present photoemission experiments on the hole doped Haldane chain compound $Y_{2-x}Sr_xBaNiO_5$. By using the photon energy dependence of the photoemission cross section, we identified the symmetry of the first ionisation states (d type). Hole doping in this system leads to a significant increase in the spectral weight at the top of the valence band without any change in the vicinity of the Fermi energy. This behavior, not observed in other charge transfer oxides at low doping level, could result from the inhomogeneous character of the doped system and from a Ni 3d-O 2p hybridization enhancement due to the shortening of the relevant Ni-O distance in the localized hole-doped regions.

cond-mat.str-el↗