The bulk-boundary correspondence is among the central issues of non-Hermitian topological states. We show that a previously overlooked "non-Hermitian skin effect" necessitates redefinition of ...topological invariants in a generalized Brillouin zone. The resultant phase diagrams dramatically differ from the usual Bloch theory. Specifically, we obtain the phase diagram of the non-Hermitian Su-Schrieffer-Heeger model, whose topological zero modes are determined by the non-Bloch winding number instead of the Bloch-Hamiltonian-based topological number. Our work settles the issue of the breakdown of conventional bulk-boundary correspondence and introduces the non-Bloch bulk-boundary correspondence.
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CsV3 Sb5 is a newly discovered Z2 topological kagome metal showing the coexistence of a charge-density-wave (CDW)-like order at T* = 94 K and superconductivity (SC) at Tc = 2.5 K at ambient pressure. ...Here, we study the interplay between CDW and SC in CsV3 Sb5 via measurements of resistivity, dc and ac magnetic susceptibility under various pressures up to 6.6 GPa. We find that the CDW transition decreases with pressure and experience a subtle modification at Pc1 ≈ 0.6 – 0.9 GPa before it vanishes completely at Pc2 ≈ 2 GPa . Correspondingly, Tc(P) displays an unusual M -shaped double dome with two maxima around Pc1 and Pc2 , respectively, leading to a tripled enhancement of Tc to about 8 K at 2 GPa. The obtained temperature-pressure phase diagram resembles those of unconventional superconductors, illustrating an intimated competition between CDW-like order and SC. The competition is found to be particularly strong for the intermediate pressure range Pc1 ≤ P ≤ Pc2 as evidenced by the broad superconducting transition and reduced superconducting volume fraction. The modification of CDW order around Pc1 has been discussed based on the band structure calculations. This work not only demonstrates the potential to raise Tc of the V-based kagome superconductors, but also offers more insights into the rich physics related to the electron correlations in this novel family of topological kagome metals.
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The FactSage computer package consists of a series of information, calculation and manipulation modules that enable one to access and manipulate compound and solution databases. With the various ...modules running under Microsoft Windows® one can perform a wide variety of thermochemical calculations and generate tables, graphs and figures of interest to chemical and physical metallurgists, chemical engineers, corrosion engineers, inorganic chemists, geochemists, ceramists, electrochemists, environmentalists, etc. This paper presents a summary of the developments in the FactSage thermochemical software and databases during the last six years. Particular emphasis is placed on the new databases and developments in calculating and manipulating phase diagrams.
Infinite-layer Nd1−xSrxNiO2 thin films with Sr doping level x from 0.08 to 0.3 are synthesized and investigated. We find a superconducting dome x between 0.12 and 0.235 accompanied by a weakly ...insulating behavior in both under- and overdoped regimes. The dome is akin to that in the electron-doped 214-type and infinite-layer cuprate superconductors. For x ≥ 0.18 , the normal state Hall coefficient ( RH ) changes the sign from negative to positive as the temperature decreases. The temperature of the sign changes decreases monotonically with decreasing x from the overdoped side and approaches the superconducting dome at the midpoint, suggesting a reconstruction of the Fermi surface with the dopant concentration across the dome.
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In order to study the thermodynamics of high entropy alloys, the evolution of the structure and microstructure of the equimolar CrMnFeCoNi high entropy alloy was investigated during ...processing under varying conditions (cooling rate and annealing duration). For the very first time, a true solid-solution down to the atomic scale was evidenced in an HEA by atom probe tomography. It was shown that this face-centered cubic single-phase solid solution is the high temperature stable state of the equimolar CrMnFeCoNi alloy. By analogy with completely miscible binary alloy, the CrMnFeCoNi HEA can be described by a schematic phase diagram of the CrFeCo–MnNi system consisting of a liquidus and a solidus, with a partition coefficient of 0.74. When the liquid phase is cooled down, dendrites enriched in Co, Cr and Fe are formed and afterward interdendrites enriched in Mn and Ni solidify. The solid solution can be reached either by a fast enough cooling or by annealing the dendritic structure, for example at 1100°C for 1h. A method to optimize the temperature and duration of an annealing of homogenization is proposed.
We solve the magnetostriction strains for B20 helimagnets in the skyrmion crystal phase. By taking MnSi as an example, we reproduce its temperature-magnetic field (T-B) phase diagrams within a ...thermodynamic potential incorporating magnetoelastic interactions. The calculation shows that the normal strain 33 undergoes a sudden jump through a conical-skyrmion phase transition at any temperature. The corresponding experimental measurements for MnSi agree quantitatively well with the calculation.
The relation between chiral edge modes and bulk Chern numbers of quantum Hall insulators is a paradigmatic example of bulk-boundary correspondence. We show that the chiral edge modes are not strictly ...tied to the Chern numbers defined by a non-Hermitian Bloch Hamiltonian. This breakdown of conventional bulk-boundary correspondence stems from the non-Bloch-wave behavior of eigenstates (non-Hermitian skin effect), which generates pronounced deviations of phase diagrams from the Bloch theory. We introduce non-Bloch Chern numbers that faithfully predict the numbers of chiral edge modes. The theory is backed up by the open-boundary energy spectra, dynamics, and phase diagram of representative lattice models. Our results highlight a unique feature of non-Hermitian bands and suggest a non-Bloch framework to characterize their topology.
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