Soft-Phonon and Charge-Density-Wave Formation in Nematic 
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Souliou, S. M.; Tom, Lacmann,; Heid, R.; Meingast, C.; Frachet, Mehdi; Paolasini, L.; Haghighirad, Amir-Abbas; Merz, Michael; Bosak, Alexeï; Tacon, M. Le

doi:10.1103/physrevlett.129.247602

Cited by 13 publications

(5 citation statements)

References 44 publications

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“…In such a scenario, a distinct possibility is that q * -CDW becomes the ground state between ∼ 2.0 GPa and ∼ 2.4 GPa, and since q * -CDW develops through phononsoftening [Fig. 3] as in 2H-NbSe 2 [64] and BaNi 2 As 2 [65,66], the corresponding resistivity anomaly would be likewise rather subtle.…”

Section: Discussionmentioning

confidence: 99%

“…CDWs usually occur via phonon softening, corresponding to coherent lattice oscillations that gradually become more competitive in energy, or the growth of a central peak that reflect the ordering of local CDW patches. The development of CDWs in one dimension as modeled by Peierls [59], and in two-dimensional systems such as 2H-NbSe 2 [64] and BaNi 2 As 2 [65,66], are accompanied by prominent phonon softening. While such phonon softening is limited to small range in momentum in Peierls' model, it occurs over an extended range in 2H-NbSe 2 and BaNi 2 As 2 , similar to the observed behavior of q * -CDW in ScV 6 Sn 6 .…”

Section: Discussionmentioning

confidence: 99%

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Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Song

Cao

et al. 2023

Preprint

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Owing to its unique geometry, the kagome lattice hosts various many-body quantum states including frustrated magnetism, superconductivity, charge-density waves (CDWs), and topologically nontrivial phases of matter. Kagome metals with 2×2 CDWs, corresponding to the nesting of van Hove saddle points, are found to exhibit a number of exotic electronic phases, and have been the focus of much recent research. More recently, a √3×√3 CDW was discovered in the kagome metal ScV6Sn6 below TCDW≈91 K, whose underlying mechanism and formation process remain unclear, particularly in comparison with the 2×2 kagome CDWs. Using inelastic X-ray scattering, we discover a short-range √3×√3×2 CDW that is dominant in ScV6Sn6 well above TCDW, distinct from the √3×√3×3 CDW below TCDW. The short-range CDW grows upon cooling, and is accompanied by the softening of phonons, indicative of its dynamic nature. As the √3×√3×3 CDW appears, the short-range CDW becomes suppressed, revealing a competition between these CDW instabilities. The competing CDW instabilities in ScV6Sn6 lead to an unusual CDW formation process, with the most pronounced phonon softening and the static CDW occurring at different wavevectors. Our first-principles calculations indicate that the √3×√3×2 CDW is energetically favored, consistent with experimental observations at high temperatures. However, the √3×√3×3 CDW is selected as the ground state due to a large wavevector-dependent electron-phonon coupling (EPC), which also accounts for the enhanced electron scattering above TCDW. Our findings reveal the dominance of EPC-driven correlated many-body physics in ScV6Sn6, making it an ideal system to study emergent quantum matter in the strong EPC regime.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Song

Cao

et al. 2023

Preprint

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“…Although it has been widely believed that these electronic orders have strong interrelation with superconductivity, their precise role in superconductivity has not been fully understood. Recently, several CDW states and the nematic order have been reported in the BaNi 2 As 2 -related superconducting materials, − which makes them a new platform for exploring the interplay between superconductivity and the intertwined orders.…”

mentioning

confidence: 99%

Real-Space Observation of Unidirectional Charge Density Wave and Complex Structural Modulation in the Pnictide Superconductor Ba_1–xSr_xNi₂As₂

et al. 2023

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Here we use low-temperature and variable-temperature scanning tunneling microscopy to study the pnictide superconductor, Ba 1−x Sr x Ni 2 As 2 . In the low-temperature phase (triclinic phase) of BaNi 2 As 2 , we observe the unidirectional charge density wave (CDW) with Q = 1/3 on both the Ba and NiAs surfaces. On the NiAs surface of the triclinic BaNi 2 As 2 , there are structural-modulation-induced chain-like superstructures with distinct periodicities. In the high-temperature phase (tetragonal phase) of BaNi 2 As 2 , the NiAs surface appears as the periodic 1 × 2 superstructure. Interestingly, in the triclinic phase of Ba 0.5 Sr 0.5 Ni 2 As 2 , the unidirectional CDW is suppressed on both the Ba/Sr and NiAs surfaces, and the Sr substitution stabilizes the periodic 1 × 2 superstructure on the NiAs surface, which enhance the superconductivity in Ba 0.5 Sr 0.5 Ni 2 As 2 . Our results provide important microscopic insights for the interplay among the unidirectional CDW, structural modulation, and superconductivity in this class of pnictide superconductors.

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“…To illustrate the complexity of the dynamics of CDW transition in real systems we point out the recently investigated BaNi 2 As 2 compound which, besides presenting a significant disorder probed by x-ray diffuse scattering, also exhibits high temperature incommensurate CDW fluctuations. It results with the softening of a damped Kohn anomaly in a TO branch, the development of a critical regime of quasi-elastic critical fluctuations closer to T P , achieving the incommensurate CDW order [295,296].…”

Section: Anti-adiabatic Regimementioning

confidence: 98%

Structural approach to charge density waves in low-dimensional systems: electronic instability and chemical bonding

Pouget,

Canadell

2024

Rep. Prog. Phys.

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Abstract. The charge density wave (CDW) instability, usually occurring in low-dimensional materials, has been a topic of interest for longtime. However, some very fundamental aspects of the mechanism remain unclear. Recently, a plethora of new CDW materials, a substantial fraction of which is 2D (two-dimensional) or even 3D (three-dimensional), has been prepared and characterized as bulk and/or single-layers. As a result, the need for revisiting the primary mechanism of the instability, based on the electron-hole instability established more than 50 years ago for quasi-1D (quasi-one-dimensional) conductors, has clearly emerged. In this work, we consider a large number of CDW materials to revisit the main concepts used in understanding the CDW instability, and emphasize the key role of the momentum dependent electron-phonon coupling in linking electronic and structural degrees of freedom. We argue that for quasi-1D systems, earlier weak coupling theories work appropriately and the energy gain due to the CDW and the concomitant periodic lattice distortion (PLD) remains primarily due to a Fermi surface nesting mechanism. However, for materials with higher dimensionality, intermediate and strong coupling regimes are generally at work and the modification of the chemical bonding network by the PLD is at the heart of the instability. We emphasize the need for a microscopic approach blending condensed matter physics concepts and state-of-the-art first-principles calculations with quite fundamental chemical bonding ideas in understanding the CDW phenomenon in these materials.

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Soft-Phonon and Charge-Density-Wave Formation in Nematic BaNi2As2

Cited by 13 publications

References 44 publications

Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Real-Space Observation of Unidirectional Charge Density Wave and Complex Structural Modulation in the Pnictide Superconductor Ba_1–xSr_xNi₂As₂

Structural approach to charge density waves in low-dimensional systems: electronic instability and chemical bonding

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Soft-Phonon and Charge-Density-Wave Formation in Nematic BaNi2As2

Cited by 13 publications

References 44 publications

Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Competing charge-density wave instabilities in the kagome metal ScV6Sn6

Real-Space Observation of Unidirectional Charge Density Wave and Complex Structural Modulation in the Pnictide Superconductor Ba1–xSrxNi2As2

Structural approach to charge density waves in low-dimensional systems: electronic instability and chemical bonding

Contact Info

Product

Resources

About

Real-Space Observation of Unidirectional Charge Density Wave and Complex Structural Modulation in the Pnictide Superconductor Ba_1–xSr_xNi₂As₂