Tuning the Van Hove singularities in AV3Sb5 (A=K,Rb,Cs) via pressure and doping
About: This article is published in Physical Review B.The article was published on 2021-11-23 and is currently open access. It has received 25 citations till now.
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TL;DR: The recently discovered kagome metal CsV${}_{3}$Sb${}{5}$ displays a superconducting transition at low temperature accompanied by a charge density wave ordering at higher temperature, among many other interesting features that arise from nested saddle points near the Fermi energy as discussed by the authors .
Abstract: The recently discovered kagome metal CsV${}_{3}$Sb${}_{5}$ displays a superconducting transition at low temperature accompanied by a charge density wave ordering at higher temperature, among many other interesting features that arise from nested saddle points near the Fermi energy. Through careful hole doping via partial substitution of Sn in the in-plane kagome Sb site, double-dome superconductivity and suppressed charge density wave order were observed. These phenomena can be partially explained by modeling the evolution of electronic band structure and changes in Fermi surface.
43 citations
TL;DR: In this article , the authors carried out high-pressure electrical measurements up to 150 GPa, together with high pressure x-ray diffraction measurements and first-principles calculations on CsV_{3}Sb_{5} and found the new superconducting phase to be rather robust and inherently linked to the interlayer Sb2-Sb2 interactions.
Abstract: The recently discovered kagome superconductors AV_{3}Sb_{5} exhibit tantalizing high-pressure phase diagrams, in which a new domelike superconducting phase emerges under moderate pressure. However, its origin is as yet unknown. Here, we carried out the high-pressure electrical measurements up to 150 GPa, together with the high-pressure x-ray diffraction measurements and first-principles calculations on CsV_{3}Sb_{5}. We find the new superconducting phase to be rather robust and inherently linked to the interlayer Sb2-Sb2 interactions. The formation of Sb2-Sb2 bonds at high pressure tunes the system from two-dimensional to three-dimensional and pushes the p_{z} orbital of Sb2 upward across the Fermi level, resulting in enhanced density of states and increase of T_{C}. Our work demonstrates that the dimensional crossover at high pressure can induce a topological phase transition and is related to the abnormal high-pressure T_{C} evolution. Our findings should apply for other layered materials.
17 citations
TL;DR: In this paper , the authors performed a search for the lowest energy structure of kagome materials using first-principles calculations and showed that there are 17 different distortions that are possible due to the phonon instabilities.
Abstract: The recently discovered kagome metals ${\mathrm{KV}}_{3}{\mathrm{Sb}}_{5}$, ${\mathrm{RbV}}_{3}{\mathrm{Sb}}_{5}$, and ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ exhibit a unique charge density wave state which hosts both superconductivity and a large anomalous Hall response. The microscopic mechanisms that underlie these phenomena have not been fully understood because the structure of the charge density wave order has not been completely determined. Previous theoretical results show that the parent $P6/mmm$ phase of these materials has phonon instabilities at the $M(\frac{1}{2},0,0)$ and $L(\frac{1}{2},0,\frac{1}{2})$ points in their Brillouin zone, but the energetics of all the low-symmetry phases that can arise due to the phonon instabilities was not investigated. Here, I perform such a search for the lowest-energy structure of these materials using first-principles calculations. Group-theoretical analysis shows that there are 17 different distortions that are possible due to the phonon instabilities. I generated these structures for the three compounds and performed full structural relaxations that minimize the atomic forces and lattice stresses. I find that the $Fmmm$ phase with the order parameter ${M}_{1}^{+}(a,0,0)+{L}_{2}^{\ensuremath{-}}(0,b,b)$ has the lowest energy among these possibilities in all three compounds. However, the $Fmmm$ exhibits a dynamical instability at its $Z(0,0,1)$ point, which corresponds to a doubly degenerate unstable phonon mode at the $A(0,0,\frac{1}{2})$ point in the parent $P6/mmm$ phase. The $A$ point has only one element in its star, and condensation of the instability at this point leads to a base-centered-orthorhombic structure with the space group $Cmcm$ and $4Q$ order parameter ${M}_{1}^{+}(a,0,0)+{L}_{2}^{\ensuremath{-}}(0,b,b)+{A}_{6}^{+}(\frac{1}{2}c,\frac{\ensuremath{-}\sqrt{3}}{2}c)$. A characteristic signature of this charge order is the absence of the mirror symmetry perpendicular to the $b$ axis in individual kagome layers, whose experimental observation below the structural transition temperature would be a strong indication that the $Cmcm$ structure describes the charge density wave state of these materials.
15 citations
TL;DR: In this article , the authors summarize the recent experimental findings and theoretical proposals and envision the materials as new platforms to study the interplay between topological physics and strongly correlated electronic systems.
Abstract: Following the discovery of a new family of kagomé prototypical materials with structure AV3Sb5 ( A=K, Rb, and Cs), there has been a heightened interest in studying the correlation-driven electronic phenomena in these kagomé lattice systems. The study of these materials has gone beyond magneto-transport measurements to reveal exciting features such as Dirac bands, anomalous Hall effect, bulk superconductivity with Tc∼0.9−2.5K, and the observation of charge density wave instabilities, suggesting an intertwining of topological physics and new quantum orders. Moreover, very recent works on numerous types of experiments have appeared further examining the unconventional superconductivity and the exotic electronic states found within these kagomé materials. Theories on the strong interactions that play a role in these systems have been proposed to shed light on the nature of these topological charge density waves. In this brief review, we summarize these recent experimental findings and theoretical proposals and envision the materials as new platforms to study the interplay between topological physics and strongly correlated electronic systems.
13 citations
TL;DR: In this paper , the structural and electronic properties of kagome metals were investigated under isotropic and anisotropic pressure, and it was shown that a Van Hove point can be shifted to the Fermi energy.
Abstract: From first-principles calculations, we investigate the structural and electronic properties of the kagome metals ${A\mathrm{V}}_{3}{\mathrm{Sb}}_{5}$ $(A=\mathrm{Cs}, \mathrm{K}, \mathrm{Rb})$ under isotropic and anisotropic pressure. Charge-ordering patterns are found to be unanimously suppressed, while there is a significant rearrangement of $p$-type and $m$-type Van Hove point energies with respect to the Fermi level. Already for moderate tensile strain along the V plane and compressive strain normal to the V layer, we find that a Van Hove point can be shifted to the Fermi energy. Such a mechanism provides an invaluable tuning knob to alter the correlation profile in the kagome metal, and suggests itself for further experimental investigation. It might allow us to reconcile possible multidome superconductivity in kagome metals not only from phonons but also from the viewpoint of unconventional pairing.
9 citations
References
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TL;DR: A simple derivation of a simple GGA is presented, in which all parameters (other than those in LSD) are fundamental constants, and only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked.
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif
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TL;DR: An efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set is presented and the application of Pulay's DIIS method to the iterative diagonalization of large matrices will be discussed.
Abstract: We present an efficient scheme for calculating the Kohn-Sham ground state of metallic systems using pseudopotentials and a plane-wave basis set. In the first part the application of Pulay's DIIS method (direct inversion in the iterative subspace) to the iterative diagonalization of large matrices will be discussed. Our approach is stable, reliable, and minimizes the number of order ${\mathit{N}}_{\mathrm{atoms}}^{3}$ operations. In the second part, we will discuss an efficient mixing scheme also based on Pulay's scheme. A special ``metric'' and a special ``preconditioning'' optimized for a plane-wave basis set will be introduced. Scaling of the method will be discussed in detail for non-self-consistent and self-consistent calculations. It will be shown that the number of iterations required to obtain a specific precision is almost independent of the system size. Altogether an order ${\mathit{N}}_{\mathrm{atoms}}^{2}$ scaling is found for systems containing up to 1000 electrons. If we take into account that the number of k points can be decreased linearly with the system size, the overall scaling can approach ${\mathit{N}}_{\mathrm{atoms}}$. We have implemented these algorithms within a powerful package called VASP (Vienna ab initio simulation package). The program and the techniques have been used successfully for a large number of different systems (liquid and amorphous semiconductors, liquid simple and transition metals, metallic and semiconducting surfaces, phonons in simple metals, transition metals, and semiconductors) and turned out to be very reliable. \textcopyright{} 1996 The American Physical Society.
81,985 citations
IBM1
TL;DR: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way and can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function.
Abstract: An approach for electronic structure calculations is described that generalizes both the pseudopotential method and the linear augmented-plane-wave (LAPW) method in a natural way. The method allows high-quality first-principles molecular-dynamics calculations to be performed using the original fictitious Lagrangian approach of Car and Parrinello. Like the LAPW method it can be used to treat first-row and transition-metal elements with affordable effort and provides access to the full wave function. The augmentation procedure is generalized in that partial-wave expansions are not determined by the value and the derivative of the envelope function at some muffin-tin radius, but rather by the overlap with localized projector functions. The pseudopotential approach based on generalized separable pseudopotentials can be regained by a simple approximation.
61,450 citations
TL;DR: An updated version of wannier90 is presented, wannIER90 2.0, including minor bug fixes and parallel (MPI) execution for band-structure interpolation and the calculation of properties such as density of states, Berry curvature and orbital magnetisation.
1,654 citations
TL;DR: The WIEN2k program is based on the augmented plane wave plus local orbitals (APW+lo) method to solve the Kohn-Sham equations of density functional theory, and the various options, properties, and available approximations for the exchange-correlation functional are mentioned.
Abstract: The WIEN2k program is based on the augmented plane wave plus local orbitals (APW+lo) method to solve the Kohn-Sham equations of density functional theory. The APW+lo method, which considers all electrons (core and valence) self-consistently in a full-potential treatment, is implemented very efficiently in WIEN2k, since various types of parallelization are available and many optimized numerical libraries can be used. Many properties can be calculated, ranging from the basic ones, such as the electronic band structure or the optimized atomic structure, to more specialized ones such as the nuclear magnetic resonance shielding tensor or the electric polarization. After a brief presentation of the APW+lo method, we review the usage, capabilities, and features of WIEN2k (version 19) in detail. The various options, properties, and available approximations for the exchange-correlation functional, as well as the external libraries or programs that can be used with WIEN2k, are mentioned. References to relevant applications and some examples are also given.
1,016 citations