The high-pressure phase diagram of BaNi${}_2$As${}_2$: unconventional charge-density-waves and structural phase transitions

Abstract

Structural phase transitions accompanied by incommensurate and commensurate charge density wave (CDW) modulations of unconventional nature have been reported in BaNi${}_2$As${}_2$, a nonmagnetic cousin of the parent compound of Fe-based superconductors, BaFe${}_2$As${}_2$. The strong dependence of the structural and CDW transitions of BaNi${}_2$As${}_2$ on isoelectronic substitutions alongside original dynamical lattice effects suggests strong tunability of the electronic phase of the system through structural effects. Here, we present a comprehensive synchrotron x-ray diffraction and first-principles calculation study of the evolution of the crystal structure and lattice instabilities of BaNi${}_2$As${}_2$ as a function of temperature and hydrostatic pressure (up to 12 GPa). We report a cascade of pressure-induced structural phase transitions and electronic instabilities up to 10 GPa, above which all CDW superstructures disappear. We reveal that the stable high-pressure phase consists of planar Ni zigzag chains, from which the surrounding As atoms have been pushed away. This yields a strong reduction of the interlayer As-As distance (along the original c axis), akin to what is observed in the collapsed tetragonal structure of other pnictides, albeit here with a monoclinic structure. The discovery of polymorphs in the pressure-temperature phase diagram of BaNi${}_2$As${}_2$ emphasizes the importance of the relative Ni-Ni and Ni-As bond lengths in controlling the electronic ground state of this compound and increases our understanding of viable electronic phases under extreme conditions.

10 pages, 5 figures, 1 table, published version

References in corpus (16)

• Pressure-induced volume-collapsed tetragonal phase of CaFe2As2 as seen via neutron scattering
• Unusual competition of superconductivity and charge-density-wave state in a compressed topological kagome metal
• Electron-Hole Symmetry and Magnetic Coupling in Antiferromagnetic LaOFeAs
• The Unprecedented Giant Coupling of Fe-spin State and the As-As Hybridization in Iron-Pnictide
• First Order Phase Transition and Superconductivity in BaNi2As2 Single Crystals
• Structure and Anisotropic Properties of BaFe2-xNixAs2 (x = 0, 1, 2) Single Crystals
• Pressure dependence of the charge-density-wave and superconducting states in GdTe${}_3$, TbTe${}_3$ and DyTe${}_3$
• Density functional study of BaNi${}_2$As${}_2$: Electronic structure, phonons and electron-phonon superconductivity
• Giant Phonon Softening and Enhancement of Superconductivity by Phosphorus Doping of BaNi2As2
• 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${}_2$
• Elastoresistivity in the incommensurate charge density wave phase of BaNi${}_{\text{2}}$(As${}_{\text{1-x}}$P${}_{\text{x}}$)${}_{\text{2}}$
• Soft-phonon and charge-density-wave formation in nematic 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
• Complex structure due to As bonding and interplay with electronic structure in superconducting BaNi2As2
• Charge Order Evolution of Superconducting BaNi2As2 Under High Pressure

Cited by in corpus (4)

• Pressure-dependent Electronic Superlattice in the Kagome-Superconductor CsV${}_3$Sb${}_5$
• 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${}_x$)${}_2$
• Orbital Ordering in the Charge Density Wave Phases of BaNi${}_2$(As${}_{1-x}$P${}_x$)${}_2$