Soft-phonon and charge-density-wave formation in nematic BaNi${}_2$As${}_2$

Abstract

We use diffuse and inelastic x-ray scattering to study the formation of an incommensurate charge-density-wave (I-CDW) in BaNi${}_2$As${}_2$, a candidate system for charge-driven electronic nematicity. Intense diffuse scattering is observed around the modulation vector of the I-CDW, $Q_{I-CDW}$. It is already visible at room temperature and collapses into superstructure reflections in the long-range ordered state where a small orthorhombic distortion occurs. A clear dip in the dispersion of a low-energy transverse optical phonon mode is observed around $Q_{I-CDW}$. The phonon continuously softens upon cooling, ultimately driving the transition to the I-CDW state. The transverse character of the soft-phonon branch elucidates the complex pattern of the I-CDW satellites observed in the current and earlier studies and settles the debated unidirectional nature of the I-CDW. The phonon instability and its reciprocal space position is well captured by our $ab$ $initio$ calculations. These however indicate that neither Fermi surface nesting, nor enhanced momentum-dependent electron-phonon coupling can account for the I-CDW formation, demonstrating its unconventional nature.% and suggest alternative origins of the I-CDW.

Revised version - to appear in PRL

References in corpus (14)

• Evidence for an electron nematic phase transition in underdoped iron pnictide superconductors
• Observation of Unconventional Charge Density Wave without Acoustic Phonon Anomaly in Kagome Superconductors AV3Sb5 (A=Rb,Cs)
• First Order Phase Transition and Superconductivity in BaNi2As2 Single Crystals
• Structure and Anisotropic Properties of BaFe2-xNixAs2 (x = 0, 1, 2) Single Crystals
• Charge Order from Orbital-dependent Coupling Evidenced by NbSe${}_2$
• Density functional study of BaNi${}_2$As${}_2$: Electronic structure, phonons and electron-phonon superconductivity
• Orbital-dependent singlet dimers and orbital-selective Peierls transitions in transition metal compounds
• Giant Phonon Softening and Enhancement of Superconductivity by Phosphorus Doping of BaNi2As2
• Charge density waves and Fermi-surface reconstruction in the clean overdoped cuprate superconductor Tl2Ba2CuO6+x
• Multiple charge density waves and superconductivity nucleation at antiphase domain walls in the nematic pnictide Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$
• An Electronic Nematic Liquid in BaNi${}_2$As${}_2$
• Electronic structure of BaNi${}_2$As${}_2$
• Rotational symmetry breaking at the incommensurate charge-density-wave transition in Ba(Ni,Co)${}_2$(As,P)${}_2$: Possible nematic phase induced by charge/orbital fluctuations
• Evidence for nesting driven charge density waves instabilities in a quasi-two-dimensional material: LaAgSb2

Cited by in corpus (18)

• Competing charge-density wave instabilities in the kagome metal ScV${}_6$Sn${}_6$
• Possible enhancement of the superconducting $T_c$ due to sharp Kohn-like soft phonon anomalies
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• Pressure-dependent Electronic Superlattice in the Kagome-Superconductor CsV${}_3$Sb${}_5$
• Precursor phase with full phonon softening above the charge-density-wave phase transition in $2H$-TaSe${}_2$
• Potential Lifshitz transition at optimal substitution in nematic pnictide Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$
• Real-space Observation of Unidirectional Charge Density Wave and Complex Structural Modulation in the Pnictide Superconductor Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$
• Spectral Evidence for Unidirectional Charge Density Wave in Detwinned BaNi${}_2$As${}_2$
• Charge order near the antiferromagnetic quantum critical point in the trilayer high $T_c$ cuprate HgBa${}_2$Ca${}_2$Cu${}_3$O${}_{8+\delta }$
• The high-pressure phase diagram of BaNi${}_2$As${}_2$: unconventional charge-density-waves and structural phase transitions
• Charge-density-wave quantum critical point under pressure in 2$H$-TaSe${}_2$
• Strong electron-phonon coupling in Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$
• Hybridization of lattice and charge order excitations in a superconducting cuprate
• Charge Order Evolution of Superconducting BaNi2As2 Under High Pressure
• Chemical pressure tuning of competing orders in ${\text{Ba}}_{1-x}{\text{Ca}}_x{\text{Ni}}_2{\text{As}}_2$
• Charge density waves and soft phonon evolution in the superconductor BaNi${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Evolution of charge-density-wave soft phonon modes in ${\mathrm{Pd}}_x{\mathrm{ErTe}}_3$
• Orbital Ordering in the Charge Density Wave Phases of BaNi${}_2$(As${}_{1-x}$P${}_x$)${}_2$