Armando Consiglio

Bio: Armando Consiglio is an academic researcher from University of Würzburg. The author has contributed to research in topics: Physics & Wright. The author has an hindex of 5, co-authored 17 publications receiving 66 citations.

Nature of Unconventional Pairing in the Kagome Superconductors A V 3 Sb 5 ( A = K , Rb , Cs )

Abstract: The recent discovery of $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ ($A=\mathrm{K},\mathrm{Rb},\mathrm{Cs}$) has uncovered an intriguing arena for exotic Fermi surface instabilities in a kagome metal. Among them, superconductivity is found in the vicinity of multiple van Hove singularities, exhibiting indications of unconventional pairing. We show that the sublattice interference mechanism is central to understanding the formation of superconductivity in a kagome metal. Starting from an appropriately chosen minimal tight-binding model with multiple van Hove singularities close to the Fermi level for $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$, we provide a random phase approximation analysis of superconducting instabilities. Nonlocal Coulomb repulsion, the sublattice profile of the van Hove bands, and the interaction strength turn out to be the crucial parameters to determine the preferred pairing symmetry. Implications for potentially topological surface states are discussed, along with a proposal for additional measurements to pin down the nature of superconductivity in $A{\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$.

The Wright functions of the second kind in Mathematical Physics

Abstract: In this review paper we stress the importance of the higher transcendental Wright functions of the second kind in the framework of Mathematical Physics.We first start with the analytical properties of the classical Wright functions of which we distinguish two kinds. We then justify the relevance of the Wright functions of the second kind as fundamental solutions of the time-fractional diffusion-wave equations. Indeed, we think that this approach is the most accessible point of view for describing non-Gaussian stochastic processes and the transition from sub-diffusion processes to wave propagation. Through the sections of the text and suitable appendices we plan to address the reader in this pathway towards the applications of the Wright functions of the second kind. Keywords: Fractional Calculus, Wright Functions, Green's Functions, Diffusion-Wave Equation,

The Wright Functions of the Second Kind in Mathematical Physics

Abstract: In this review paper, we stress the importance of the higher transcendental Wright functions of the second kind in the framework of Mathematical Physics. We first start with the analytical properties of the classical Wright functions of which we distinguish two kinds. We then justify the relevance of the Wright functions of the second kind as fundamental solutions of the time-fractional diffusion-wave equations. Indeed, we think that this approach is the most accessible point of view for describing non-Gaussian stochastic processes and the transition from sub-diffusion processes to wave propagation. Through the sections of the text and suitable appendices, we plan to address the reader in this pathway towards the applications of the Wright functions of the second kind.

Momentum for Catalysis: How Surface Reactions Shape the RuO2 Flat Surface State

Abstract: The active (110) surface of the benchmark oxygen evolution catalyst RuO2 spans a flat-band surface state (FBSS) between the surface projections of its Dirac nodal lines (DNLs) that define the elect...

On the evolution of fractional diffusive waves

Abstract: In physics, phenomena of diffusion and wave propagation have great relevance; these physical processes are governed in the simplest cases by partial differential equations of order 1 and 2 in time, respectively. It is known that whereas the diffusion equation describes a process where the disturbance spreads infinitely fast, the propagation velocity of the disturbance is a constant for the wave equation. By replacing the time derivatives in the above standard equations with pseudo-differential operators interpreted as derivatives of non integer order (nowadays misnamed as of fractional order) we are lead to generalized processes of diffusion that may be interpreted as slow diffusion and interpolating between diffusion and wave propagation. In mathematical physics, we may refer these interpolating processes to as fractional diffusion-wave phenomena. The use of the Laplace transform in the analysis of the Cauchy and Signalling problems leads to special functions of the Wright type. In this work we analyze and simulate both the situations in which the input function is a Dirac delta generalized function and a box function, restricting ourselves to the Cauchy problem. In the first case we get the fundamental solutions (or Green functions) of the problem whereas in the latter case the solutions are obtained by a space convolution of the Green function with the input function. In order to clarify the matter for the non-specialist readers, we briefly recall the basic and essential notions of the fractional calculus (the mathematical theory that regards the integration and differentiation of non-integer order) with a look at the history of this discipline.

Time-reversal symmetry-breaking charge order in a kagome superconductor

Abstract: The kagome lattice1, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders2-8 and, most rarely, to unconventional superconductivity6,9. Recently, charge sensitive probes have indicated that the kagome superconductors AV3Sb5 (A = K, Rb, Cs)9-11 exhibit unconventional chiral charge order12-19, which is analogous to the long-sought-after quantum order in the Haldane model20 or Varma model21. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KV3Sb5. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KV3Sb5 and that the [Formula: see text] ratio (where Tc is the superconducting transition temperature and λab is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.

Twofold van Hove singularity and origin of charge order in topological kagome superconductor CsV3Sb5

Abstract: The electronic band structure of the 2D kagome net hosts two different types of van Hove singularities (vHs) arising from an intrinsic electron-hole asymmetry. The distinct sublattice flavors (pure and mixed, p-type and m-type) and pairing instabilities associated to the two types of vHs are key to understand the unconventional many-body phases of the kagome lattice. Here, in a recently discovered kagome metal CsV3Sb5 exhibiting charge order and superconductivity, we have examined the vHs, Fermi surface nesting, and many-body gap opening. Using high-resolution angle-resolved photoemission spectroscopy (ARPES), we identify multiple vHs coexisting near the Fermi level of CsV3Sb5, including both p- and m-types of vHs emerging from dxz/dyz kagome bands and a p-type vHs from dxy/dx2-y2 kagome bands. Among the multiple vHs, the m-type vHs is located closest to the Fermi level and is characterized by sharp Fermi surface nesting and gap opening across the charge order transition. Our work reveals the essential role of kagome-derived vHs as a driving mechanism for the collective phenomena realized in the AV3Sb5 family (A = K, Rb, Cs) and paves the way for a deeper understanding of strongly correlated topological kagome systems.

Introduction to Fractional Calculus

Abstract: In this chapter, fractional calculus is introduced. After a brief overview about this topic, some basic definitions and properties are presented. Moreover, some geometrical and physical interpretations of fractional operators are described, both in time and frequency domain.

Electronic nature of chiral charge order in the kagome superconductor Cs V 3 Sb 5

Abstract: Author(s): Wang, Z; Jiang, YX; Yin, JX; Li, Y; Wang, GY; Huang, HL; Shao, S; Liu, J; Zhu, P; Shumiya, N; Hossain, MS; Liu, H; Shi, Y; Duan, J; Li, X; Chang, G; Dai, P; Ye, Z; Xu, G; Wang, Y; Zheng, H; Jia, J; Hasan, MZ; Yao, Y | Abstract: Kagome superconductors with TC up to 7 K have been discovered for over 40 y. Recently, unconventional chiral charge order has been reported in kagome superconductor KV3Sb5, with an ordering temperature of one order of magnitude higher than the TC. However, the chirality of the charge order has not been reported in the cousin kagome superconductor CsV3Sb5, and the electronic nature of the chirality remains elusive. In this paper, we report the observation of electronic chiral charge order in CsV3Sb5 via scanning tunneling microscopy (STM). We observe a 2 × 2 charge modulation and a 1 × 4 superlattice in both topographic data and tunneling spectroscopy. 2 × 2 charge modulation is highly anticipated as a charge order by fundamental kagome lattice models at van Hove filling, and is shown to exhibit intrinsic chirality. We find that the 1 × 4 superlattices form various small domain walls, and can be a surface effect as supported by our first-principles calculations. Crucially, we find that the amplitude of the energy gap opened by the charge order exhibits real-space modulations, and features 2 × 2 wave vectors with chirality, highlighting the electronic nature of the chiral charge order. STM study at 0.4 K reveals a superconducting energy gap with a gap size 2Δ=0.85meV, which estimates a moderate superconductivity coupling strength with 2Δ/kBTC=3.9. When further applying a c-axis magnetic field, vortex core bound states are observed within this gap, indicative of clean-limit superconductivity.