1
|
Yao Y, Willa R, Lacmann T, Souliou SM, Frachet M, Willa K, Merz M, Weber F, Meingast C, Heid R, Haghighirad AA, Schmalian J, Le Tacon M. An electronic nematic liquid in BaNi 2As 2. Nat Commun 2022; 13:4535. [PMID: 35927267 PMCID: PMC9352674 DOI: 10.1038/s41467-022-32112-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Accepted: 07/14/2022] [Indexed: 11/25/2022] Open
Abstract
Understanding the organizing principles of interacting electrons and the emergence of novel electronic phases is a central endeavor of condensed matter physics. Electronic nematicity, in which the discrete rotational symmetry in the electron fluid is broken while the translational one remains unaffected, is a prominent example of such a phase. It has proven ubiquitous in correlated electron systems, and is of prime importance to understand Fe-based superconductors. Here, we find that fluctuations of such broken symmetry are exceptionally strong over an extended temperature range above phase transitions in \documentclass[12pt]{minimal}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{amsbsy}
\usepackage{mathrsfs}
\usepackage{upgreek}
\setlength{\oddsidemargin}{-69pt}
\begin{document}$${{{{{\rm{Ba}}}}}}{{{{{{\rm{Ni}}}}}}}_{2}{({{{{{{\rm{As}}}}}}}_{1-x}{{{{{{\rm{P}}}}}}}_{x})}_{2}$$\end{document}BaNi2(As1−xPx)2, the nickel homologue to the Fe-based systems. This lends support to a type of electronic nematicity, dynamical in nature, which exhibits a particularly strong coupling to the underlying crystal lattice. Fluctuations between degenerate nematic configurations cause splitting of phonon lines, without lifting degeneracies nor breaking symmetries, akin to spin liquids in magnetic systems. Electronic nematicity is typically associated with the breaking of rotational symmetry. Here the authors report unusual nematicity in BaNi2As2, manifested in a large splitting of the optical phonon mode above the structural transition temperature, and link it to the coupling between the lattice and nematic fluctuations.
Collapse
Affiliation(s)
- Yi Yao
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Roland Willa
- Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131, Karlsruhe, Germany
| | - Tom Lacmann
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Sofia-Michaela Souliou
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Mehdi Frachet
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Kristin Willa
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Michael Merz
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany.,Karlsruhe Nano Micro Facility (KNMFi), Karlsruhe Institute of Technology (KIT), 76344, Eggenstein-Leopoldshafen, Germany
| | - Frank Weber
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Christoph Meingast
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Rolf Heid
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Amir-Abbas Haghighirad
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany
| | - Jörg Schmalian
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany.,Institut für Theorie der Kondensierten Materie, Karlsruher Institut für Technologie, 76131, Karlsruhe, Germany
| | - Matthieu Le Tacon
- Institut für Quantenmaterialien und -technologien, Karlsruher Institut für Technologie, 76021, Karlsruhe, Germany.
| |
Collapse
|
2
|
Abstract
We report results of low-temperature heat-capacity, magnetocaloric-effect, and neutron-diffraction measurements of TmVO4, an insulator that undergoes a continuous ferroquadrupolar phase transition associated with local partially filled 4f orbitals of the thulium (Tm[Formula: see text]) ions. The ferroquadrupolar transition, a realization of Ising nematicity, can be tuned to a quantum critical point by using a magnetic field oriented along the c axis of the tetragonal crystal lattice, which acts as an effective transverse field for the Ising-nematic order. In small magnetic fields, the thermal phase transition can be well described by using a semiclassical mean-field treatment of the transverse-field Ising model. However, in higher magnetic fields, closer to the field-tuned quantum phase transition, subtle deviations from this semiclassical behavior are observed, which are consistent with expectations of quantum fluctuations. Although the phase transition is driven by the local 4f degrees of freedom, the crystal lattice still plays a crucial role, both in terms of mediating the interactions between the local quadrupoles and in determining the critical scaling exponents, even though the phase transition itself can be described via mean field. In particular, bilinear coupling of the nematic order parameter to acoustic phonons changes the spatial and temporal fluctuations of the former in a fundamental way, resulting in different critical behavior of the nematic transverse-field Ising model, as compared to the usual case of the magnetic transverse-field Ising model. Our results establish TmVO4 as a model material and electronic nematicity as a paradigmatic example for quantum criticality in insulators.
Collapse
|
3
|
Wu S, Song Y, He Y, Frano A, Yi M, Chen X, Uchiyama H, Alatas A, Said AH, Wang L, Wolf T, Meingast C, Birgeneau RJ. Short-Range Nematic Fluctuations in Sr_{1-x}Na_{x}Fe_{2}As_{2} Superconductors. PHYSICAL REVIEW LETTERS 2021; 126:107001. [PMID: 33784111 DOI: 10.1103/physrevlett.126.107001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 02/02/2021] [Indexed: 06/12/2023]
Abstract
Interactions between nematic fluctuations, magnetic order and superconductivity are central to the physics of iron-based superconductors. Here we report on in-plane transverse acoustic phonons in hole-doped Sr_{1-x}Na_{x}Fe_{2}As_{2} measured via inelastic x-ray scattering, and extract both the nematic susceptibility and the nematic correlation length. By a self-contained method of analysis, for the underdoped (x=0.36) sample, which harbors a magnetically ordered tetragonal phase, we find it hosts a short nematic correlation length ξ∼10 Å and a large nematic susceptibility χ_{nem}. The optimal-doped (x=0.55) sample exhibits weaker phonon softening effects, indicative of both reduced ξ and χ_{nem}. Our results suggest short-range nematic fluctuations may favor superconductivity, placing emphasis on the nematic correlation length for understanding the iron-based superconductors.
Collapse
Affiliation(s)
- Shan Wu
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Yu Song
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Yu He
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Alex Frano
- Department of Physics, University of California, San Diego, California 92093, USA
| | - Ming Yi
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Xiang Chen
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Hiroshi Uchiyama
- Japan Synchrotron Radiation Research Institute, SPring-8, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
| | - Ahmet Alatas
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Ayman H Said
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - Liran Wang
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Thomas Wolf
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Christoph Meingast
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany
| | - Robert J Birgeneau
- Department of Physics, University of California, Berkeley, California 94720, USA
- Material Sciences Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| |
Collapse
|