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

Abstract

Nematic phase transitions in high-temperature superconductors have a strong impact on the electronic properties of these systems. BaFe${}_2$As${}_2$,\@ with an established nematic transition around 137 K induced by magnetic fluctuations, and BaNi${}_2$As${}_2$,\@ a non-magnetic analog of BaFe${}_2$As${}_2$ with a structural transition in the same temperature range,\@ share a common tetragonal aristotype crystal structure with space-group type $I4/mmm$.\@ In contrast to BaFe${}_2$As${}_2$ where collinear stripe magnetic order is found for the orthorhombic low-$T$ phase, a unidirectional charge density wave together with (distorted) zig-zag chains are observed for the triclinic low-$T$ phase of BaNi${}_2$As${}_2$.\@ Here we show that between the high- and low-$T$ phases of Ba(Ni,Co)${}_2$(As,P)${}_2$ an additional phase with broken fourfold symmetry and $d_{xz}$ orbital order exists which is a promising candidate for charge/orbital-fluctuation-induced nematicity. Moreover, our data suggest that the enhanced $T_{\mathrm{c}}$ found for Ba(Ni,Co)${}_2$(As,P)${}_2$ for higher Co or P substitution levels might result from suppression of the (distorted) zig-zag chains by reducing the contribution of the $d_{xy}$ orbitals.

arXiv comment17 pages, 20 figures, submitted

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Cited by in corpus (15)

• 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${}_2$
• Phonon softening and slowing down of charge-density-wave fluctuations in BaNi${}_2$As${}_2$
• 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${}_2$
• Complex structure due to As bonding and interplay with electronic structure in superconducting BaNi2As2
• 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${}_2$
• The high-pressure phase diagram of BaNi${}_2$As${}_2$: unconventional charge-density-waves and structural phase transitions
• Strong electron-phonon coupling in Ba${}_{1-x}$Sr${}_x$Ni${}_2$As${}_2$
• I-centered vs F-centered orthorhombic symmetry and negative thermal expansion of the charge density wave of EuAl2Ga2
• 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${}_x$)${}_2$