arXiv subjects

B. Vignolle

Publications and source records attributed to B. Vignolle.

At least 19 recordsLinked to original sources

arXiv2026

Pressure-Driven Structural Transitions without a Displacive Charge-Density Wave in La$_2$SmNi$_2$O$_7$

We investigated the structural properties of bilayer nickelate La$_2$SmNi$_2$O$_7$ as a function of pressure and temperature. At ambient conditions, we show that the material crystallizes as a monoclinic superstructure distinct from the one previously reported and close to the pseudo-orthorhombic structure of pristine La$_3$Ni$_2$O$_7$. No signatures of satellite reflections associated with charge density wave (CDW) ordering are detected at low temperature. Upon compression, a sequence of pressure-induced structural transitions from monoclinic to orthorhombic 15 GPa and then tetragonal 21 GPa symmetry is observed. Within the superconducting dome, the quality of the X-ray diffraction data enables structural refinements enabling theoretical models to understand the emergence of superconductivity.

cond-mat.str-el↗

arXiv2026

Superconductivity, Kondo physics and magnetic order: Tuning the groundstate in the La$_{1-x}$Ce$_x$FeSiH solid solution through the interplay between $3d$ and $4f$ correlated electrons

We report a study of the La$_{1-x}$Ce$_x$FeSiH solid solution ($0 \leq x \leq 1$), a family of intermetallic hydrides of ZrCuSiAs-type structure, with space group $P4/nmm$. For low cerium concentrations $x \leq 0.20$, we observe the presence of superconductivity, which originates from the correlated $3d$ electrons of iron. The superconducting regime is progressively suppressed by the cerium substitution. For moderate cerium concentration $0.07 \leq x \leq 0.50$, we observe evidence of the single-ion Kondo effect and no magnetic phase transition down to 2 K. For $0.07 \leq x \leq 0.20$, the single-ion Kondo effect coexists with a superconducting ground state at low temperatures. From $x > 0.50$, we observe signatures of Kondo coherence and a heavy Fermi liquid regime at low temperature. Finally, at high cerium concentration $x \geq 0.85$, we observe signatures of magnetic ordering at low temperatures. We discuss our results by introducing temperature scales related to superconductivity, the Kondo effect, and magnetic order, which permits building a rich phase diagram temperature versus cerium content $x$. This shows that using the cerium concentration $x$ as a unique control parameter, we can explore the Kondo entanglement between correlated $3d$ and $4f$ electrons, which suggests an unusual change between the superconducting state related to the $3d$ electrons and the Kondo coherent state involving both $3d$ and $4f$ electrons.

cond-mat.str-el↗

arXiv2025

Multiband Superconductivity and High Critical Current Density in Entropy Stabilized Nb0.25Ta0.25Ti0.25Zr0.25

High and medium-entropy superconductors with significant intrinsic disorder are a fascinating class of superconductors. Their combination of robust structural integrity, superior mechanical properties, and exceptional irradiation tolerance makes them promising candidates for use in advanced superconducting technologies. Herein, we present a comprehensive theoretical and experimental investigation on the superconductivity of equiatomic entropy-stabilized Nb0.25Ta0.25Ti0.25Zr0.25. The material shows bulk superconductivity (transition temperature = 8K) with a high upper critical field of 11.94T. Interestingly, both the electronic band structure and specific heat data point toward unconventional multiband superconductivity. Our ab initio calculations reveal Dirac-like band crossings close to the Fermi level, with certain degeneracies persisting even in the presence of spin-orbit coupling, suggesting a possible interplay between topological electronic states and the observed unconventional superconductivity. Remarkably, the critical current density exceeds the benchmark of 10^5 A/cm2, surpassing all previously reported as-cast entropy-stabilized superconductors. This high critical current density is likely attributed to strong flux pinning at the grain boundaries, facilitated by extreme intrinsic lattice distortion. Taken together, the demonstrated dynamical stability, excellent metallicity, potential to host unconventional superconductivity, and exceptionally high critical current density highlight the potential of entropy-stabilized alloys as a platform for exploring the confluence of disorder, topology, and unconventional superconductivity.

cond-mat.supr-con↗

arXiv2021

Evidence for antiferromagnetism coexisting with charge order in the trilayer cuprate HgBa$_2$Ca$_2$Cu$_3$O$_{8+ δ}$

Multilayered cuprates possess not only the highest superconducting temperature transition but also offer a unique platform to study disorder-free CuO$_2$ planes and the interplay between competing orders with superconductivity. Here, we study the underdoped trilayer cuprate HgBa$_2$Ca$_2$Cu$_3$O$_{8+ δ}$ and we report the first quantum oscillation and Hall effect measurements in magnetic field up to 88 T. A careful analysis of the complex spectra of quantum oscillations strongly supports the coexistence of an antiferromagnetic order in the inner plane and a charge order in the outer planes. The presence of an ordered antiferromagnetic metallic state that extends deep in the superconducting phase is a key ingredient that supports magnetically mediated pairing interaction in cuprates.

cond-mat.supr-con↗

arXiv2021

Arc-to-pocket transition and quantitative understanding of transport properties in cuprate superconductors

Despite immense efforts, the cuprate Fermi surface (FS) has been unambiguously determined in only two distinct, low-temperature regions of the phase diagram: a large hole-like FS at high doping, and a small electron-like pocket associated with charge-density-wave driven FS reconstruction at moderate doping. Moreover, there exists incomplete understanding of the reconstructed state, which is stabilized by high magnetic fields, and its connection with the normal state that consists of arc-like remnants of the large underlying FS. Part of the problem is that compound-specific idiosyncrasies, such as disorder effects and low structural symmetry, can obscure the fundamental properties of the quintessential CuO$_2$ planes. Here we present planar magnetotransport measurements for moderately-doped HgBa$_2$CuO$_{4+δ}$ that enable a quantitative understanding of the phase transition between the normal and reconstructed states and of the charge transport in the latter, and that demonstrate that the quasiparticle scattering rate in both states is due to Umklapp scattering. Building on prior insights, we furthermore arrive at a comprehensive understanding of the evolution of the planar transport properties throughout the entire cuprate phase diagram.

cond-mat.supr-con↗

arXiv2020

High magnetic field ultrasound study of spin freezing in La$_{1.88}$Sr$_{0.12}$CuO$_4$

High-$T_{\rm{c}}$ cuprate superconductors host spin, charge and lattice instabilities. In particular, in the antiferromagnetic glass phase, over a large doping range, lanthanum based cuprates display a glass-like spin freezing with antiferromagnetic correlations. Previously, sound velocity anomalies in La$_{2-x}$Sr$_{x}$CuO$_4$ (LSCO) for hole doping $p\geq 0.145$ were reported and interpreted as arising from a coupling of the lattice to the magnetic glass [Frachet, Vinograd et al., Nat. Phys. 16, 1064-1068 (2020)]. Here we report both sound velocity and attenuation in LSCO $p=0.12$, i.e. at a doping level for which the spin freezing temperature is the highest. Using high magnetic fields and comparing with nuclear magnetic resonance (NMR) measurements, we confirm that the anomalies in the low temperature ultrasound properties of LSCO are produced by a coupling between the lattice and the spin glass. Moreover, we show that both sound velocity and attenuation can be simultaneously accounted for by a simple phenomenological model originally developed for canonical spin glasses. Our results point towards a strong competition between superconductivity and spin freezing, tuned by the magnetic field. A comparison of different acoustic modes suggests that the slow spin fluctuations have a nematic character.

cond-mat.supr-con↗

arXiv2019

Protected superconductivity at the boundaries of charge-density-wave domains

Solid 4He may acquire superfluid characteristics due to the frustration of the solid phase at grain boundaries. Here, we show that an analogous effect occurs in systems with competition among charge-density-waves (CDWs) and superconductivity in the presence of disorder, as cuprate or dichalcogenide superconductors. The CDWs breaks apart in domains with topologically protected filamentary superconductivity (FSC) at the interfaces. Transport experiments carried out in underdoped cuprates with the magnetic field acting as a control parameter are shown to be in excellent agreement with the theoretical expectation. At high temperature and low fields we find a transition from CDWs to fluctuating superconductivity, weakly affected by disorder, while at high field and low temperature the protected filamentary superconducting phase appears in close analogy with "glassy" supersolid phenomena in 4He.

cond-mat.supr-con↗

arXiv2018

Universal $T$-linear resistivity and Planckian limit in overdoped cuprates

The perfectly linear temperature dependence of the electrical resistivity observed as $T \rightarrow$ 0 in a variety of metals close to a quantum critical point is a major puzzle of condensed matter physics . Here we show that $T$-linear resistivity as $T \rightarrow$ 0 is a generic property of cuprates, associated with a universal scattering rate. We measured the low-temperature resistivity of the bi-layer cuprate Bi2212 and found that it exhibits a $T$-linear dependence with the same slope as in the single-layer cuprates Bi2201, Nd-LSCO and LSCO, despite their very different Fermi surfaces and structural, superconducting and magnetic properties. We then show that the $T$-linear coefficient (per CuO$_2$ plane), $A_1$, is given by the universal relation $A_1 T_F = h / 2e^2$, where $e$ is the electron charge, $h$ is the Planck constant and $T_F$ is the Fermi temperature. This relation, obtained by assuming that the scattering rate 1 / $τ$ of charge carriers reaches the Planckian limit whereby $\hbar / τ= k_B T$, works not only for hole-doped cuprates but also for electron-doped cuprates despite the different nature of their quantum critical point and strength of their electron correlations.

cond-mat.supr-con↗

arXiv2017

Synchrotron x-ray scattering study of charge-density-wave order in HgBa$_2$CuO$_{4+δ}$

We present a detailed synchrotron x-ray scattering study of the charge-density-wave (CDW) order in simple tetragonal HgBa$_2$CuO$_{4+δ}$ (Hg1201). Resonant soft x-ray scattering measurements reveal that short-range order appears at a temperature that is distinctly lower than the pseudogap temperature and in excellent agreement with a prior transient reflectivity result. Despite considerable structural differences between Hg1201 and YBa$_2$Cu$_3$O$_{6+δ}$, the CDW correlations exhibit similar doping dependencies, and we demonstrate a universal relationship between the CDW wave vector and the size of the reconstructed Fermi pocket observed in quantum oscillation experiments. The CDW correlations in Hg1201 vanish already below optimal doping, once the correlation length is comparable to the CDW modulation period, and they appear to be limited by the disorder potential from unit cells hosting two interstitial oxygen atoms. A complementary hard x-ray diffraction measurement, performed on an underdoped Hg1201 sample in magnetic fields along the crystallographic $c$ axis of up to 16 T, provides information about the form factor of the CDW order. As expected from the single-CuO$_2$-layer structure of Hg1201, the CDW correlations vanish at half-integer values of $L$ and appear to be peaked at integer $L$. We conclude that the atomic displacements associated with the short-range CDW order are mainly planar, within the CuO$_2$ layers.

cond-mat.supr-con↗

arXiv2017

Fermi liquid behavior of the in-plane resistivity in the pseudogap state of YBa_2Cu_4O_8

Our knowledge of the ground state of underdoped hole-doped cuprates has evolved considerably over the last few years. There is now compelling evidence that inside the pseudogap phase, charge order breaks translational symmetry leading to a reconstructed Fermi surface made of small pockets. Quantum oscillations, [Doiron-Leyraud N, et al. (2007) Nature 447:564-568], optical conductivity [Mirzaei SI, et al. (2013) Proc Natl Acad Sci USA 110:5774-5778] and the validity of Wiedemann-Franz law [Grissonnache G, et al. (2016) Phys. Rev. B 93:064513] point to a Fermi liquid regime at low temperature in the underdoped regime. However, the observation of a quadratic temperature dependence in the electrical resistivity at low temperatures, the hallmark of a Fermi liquid regime, is still missing. Here, we report magnetoresistance measurements in the magnetic-field-induced normal state of underdoped YBa_2Cu_4O_8 which are consistent with a T^2 resistivity extending down to 1.5 K. The magnitude of the T^2 coefficient, however, is much smaller than expected for a single pocket of the mass and size observed in quantum oscillations, implying that the reconstructed Fermi surface must consist of at least one additional pocket.

cond-mat.supr-con↗

arXiv2016

Onset of exciton-exciton annihilation in single layer black phosphorus

The exciton dynamics in monolayer black phosphorus is investigated over a very wide range of photoexcited exciton densities using time resolved photoluminescence. At low excitation densities, the exciton dynamics is successfully described in terms of a double exponential decay. With increasing exciton population, a fast, non-exponential component develops as exciton-exciton annihilation takes over as the dominant recombination mechanism under high excitation conditions. Our results identify an upper limit for the injection density, after which exciton-exciton annihilation reduces the quantum yield, which will significantly impact the performance of light emitting devices based on single layer black phosphorus.

cond-mat.mes-hall↗

arXiv2016

Dichotomy between Attractive and Repulsive Tomonaga-Luttinger Liquids in Spin Ladders

We present two methods to determine whether the interactions in a Tomonaga-Luttinger liquid (TLL) state of a spin-$1/2$ Heisenberg antiferromagnetic ladder are attractive or repulsive. The first method combines two bulk measurements, of magnetization and specific heat, to deduce the TLL parameter that distinguishes between the attraction and repulsion. The second one is based on a local-probe, NMR measurements of the spin-lattice relaxation. For the strong-leg spin ladder compound $\mathrm{(C_7H_{10}N)_2CuBr_4}$ we find that the isothermal magnetic field dependence of the relaxation rate, $T_1^{-1}(H)$, displays a concave curve between the two critical fields that bound the TLL regime. This is in sharp contrast to the convex curve previously reported for a strong-rung ladder $\mathrm{(C_5H_{12}N)_2CuBr_4}$. Within the TLL description, we show that the concavity directly reflects the attractive interactions, while the convexity reflects the repulsive ones.

cond-mat.str-el↗

arXiv2016

Origin of the metal-to-insulator crossover in cuprate superconductors

Superconductivity in cuprates peaks in the doping regime between a metal at high p and an insulator at low p. Understanding how the material evolves from metal to insulator is a fundamental and open question. Early studies in high magnetic fields revealed that below some critical doping an insulator-like upturn appears in the resistivity of cuprates at low temperature, but its origin has remained a puzzle. Here we propose that this 'metal-to-insulator crossover' is due to a drop in carrier density n associated with the onset of the pseudogap phase at a critical doping p*. We use high-field resistivity measurements on LSCO to show that the upturns are quantitatively consistent with a drop from n=1+p above p* to n=p below p*, in agreement with high-field Hall data in YBCO. We demonstrate how previously reported upturns in the resistivity of LSCO, YBCO and Nd-LSCO are explained by the same universal mechanism: a drop in carrier density by 1.0 hole per Cu atom.

cond-mat.supr-con↗

arXiv2016

Inverse correlation between quasiparticle mass and Tc in a cuprate high-Tc superconductor

Close to a zero temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of the electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors and there have been suggestions that high temperature superconductivity in the copper oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature $T_c$ is maximum in the cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge ordered phase. Recent experiments have shown a strong increase in quasiparticle mass $m^*$ in the cuprate YBa$_2$Cu$_3$O$_{7-δ}$ as optimal doping is approached suggesting that quantum fluctuations of the charge ordered phase may be responsible for the high-$T_c$ superconductivity. We have tested the robustness of this correlation between $m^*$ and $T_c$ by performing quantum oscillation studies on the stoichiometric compound YBa$_2$Cu$_4$O$_8$ under hydrostatic pressure. In contrast to the results for YBa$_2$Cu$_3$O$_{7-δ}$, we find that in YBa$_2$Cu$_4$O$_8$ the mass decreases as $T_c$ increases under pressure. This inverse correlation between $m^*$ and $T_c$ suggests that quantum fluctuations of the charge order enhance $m^*$ but do not enhance $T_c$.

cond-mat.supr-con↗

arXiv2015

Change of carrier density at the pseudogap critical point of a cuprate superconductor

The pseudogap is a central puzzle of cuprate superconductors. Its connection to the Mott insulator at low doping $p$ remains ambiguous and its relation to the charge order that reconstructs the Fermi surface at intermediate $p$ is still unclear. Here we use measurements of the Hall coefficient in magnetic fields up to 88 T to show that Fermi-surface reconstruction by charge order in YBa$_2$Cu$_3$O$_y$ ends sharply at a critical doping $p = 0.16$, distinctly lower than the pseudogap critical point at $p^* = 0.19$. This shows that pseudogap and charge order are separate phenomena. We then find that the change of carrier density from $n = 1 + p$ in the conventional metal at high p to $n = p$ at low $p$ - a signature of the lightly doped cuprates - starts at $p^*$. This shows that pseudogap and antiferromagnetic Mott insulator are linked.

cond-mat.supr-con↗

arXiv2015

Correlation between Fermi surface transformations and superconductivity in the electron-doped high-$T_c$ superconductor Nd$_{2-x}$Ce$_x$CuO$_4$

Two critical points have been revealed in the normal-state phase diagram of the electron-doped cuprate superconductor Nd$_{2-x}$Ce$_x$CuO$_4$ by exploring the Fermi surface properties of high quality single crystals by high-field magnetotransport. First, the quantitative analysis of the Shubnikov-de Haas effect shows that the weak superlattice potential responsible for the Fermi surface reconstruction in the overdoped regime extrapolates to zero at the doping level $x_c = 0.175$ corresponding to the onset of superconductivity. Second, the high-field Hall coefficient exhibits a sharp drop right below optimal doping $x_{\mathrm{opt}} = 0.145$ where the superconducting transition temperature is maximum. This drop is most likely caused by the onset of long-range antiferromagnetic ordering. Thus, the superconducting dome appears to be pinned by two critical points to the normal state phase diagram.

cond-mat.str-el↗

arXiv2015

Confinement of superconducting fluctuations due to emergent electronic inhomogeneities

The microscopic nature of an insulating state in the vicinity of a superconducting state, in the presence of disorder, is a hotly debated question. While the simplest scenario proposes that Coulomb interactions destroy the Cooper pairs at the transition, leading to localization of single electrons, an alternate possibility supported by experimental observations suggests that Cooper pairs instead directly localize. The question of the homogeneity, granularity, or possibly glassiness of the material on the verge of this transition is intimately related to this fundamental issue. Here, by combining macroscopic and nano-scale studies of superconducting ultrathin NbN films, we reveal nanoscopic electronic inhomogeneities that emerge when the film thickness is reduced. In addition, while thicker films display a purely two-dimensional behaviour in the superconducting fluctuations, we demonstrate a zero-dimensional regime for the thinner samples precisely on the scale of the inhomogeneities. Such behavior is somehow intermediate between the Fermi and Bose insulator paradigms and calls for further investigation to understand the way Cooper pairs continuously evolve from a bound state of fermionic objects into localized bosonic entities.

cond-mat.supr-con↗

arXiv2015

Evidence for a small hole pocket in the Fermi surface of underdoped YBa2Cu3Oy

The Fermi surface of a metal is the fundamental basis from which its properties can be understood. In underdoped cuprate superconductors, the Fermi surface undergoes a reconstruction that produces a small electron pocket, but whether there is another, as yet undetected portion to the Fermi surface is unknown. Establishing the complete topology of the Fermi surface is key to identifying the mechanism responsible for its reconstruction. Here we report the discovery of a second Fermi pocket in underdoped YBa2Cu3Oy, detected as a small quantum oscillation frequency in the thermoelectric response and in the c-axis resistance. The field-angle dependence of the frequency demonstrates that it is a distinct Fermi surface and the normal-state thermopower requires it to be a hole pocket. A Fermi surface consisting of one electron pocket and two hole pockets with the measured areas and masses is consistent with a Fermi-surface reconstruction caused by the charge-density-wave order observed in YBa2Cu3Oy, provided other parts of the reconstructed Fermi surface are removed by a separate mechanism, possibly the pseudogap.

cond-mat.supr-con↗