Quasi-2D spin-Peierls transition through interstitial anionic electrons in K(NH3)2
Chi Ding1, Qing Lu1, Zhaopeng Guo1
1National Laboratory of Solid State Microstructures, School of Physics and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China.
Science Bulletin
|February 29, 2024
Summary
Potassium and ammonia form stable compounds under pressure, revealing a novel spin-Peierls state in R3¯m K(NH₃)₂. This state features interstitial anionic electrons with unique magnetic and lattice instabilities.
Area of Science:
- Condensed Matter Physics
- Quantum Materials Science
- Materials Chemistry
Background:
- Electron-phonon and electron-electron interactions are fundamental in condensed matter.
- Spin-Peierls states arise from lattice dimerization and Coulomb repulsion in magnetic chains.
Purpose of the Study:
- To predict stable potassium-ammonia compounds under pressure.
- To investigate the electronic and magnetic properties of R3¯m K(NH₃)₂, particularly its electride characteristics.
- To explore the interplay of Peierls and magnetic instabilities in this novel material.
Main Methods:
- First-principles calculations
- Crystal structure prediction methods
- Analysis of electronic van-Hove singularity and density of states
- Investigation of magnetic and Peierls instabilities
Main Results:
- Stable potassium-ammonia compounds identified: R3¯m K(NH₃)₂, Pm3¯m K(NH₃)₂, and Cm K₂(NH₃)₃.
- R3¯m K(NH₃)₂ exhibits electride properties with quasi-2D triangular arrays of interstitial anionic electrons (IAEs).
- Increasing pressure leads to Peierls and magnetic instabilities, with the ground state being a dimerized P2₁/m phase with anti-ferromagnetic IAEs.
Conclusions:
- A novel spin-Peierls instability involving IAEs is discovered in R3¯m K(NH₃)₂.
- The coexistence and interplay of magnetic and Peierls instabilities are crucial for the observed ground state.
- This study offers insights into the coupling of IAEs with lattices and their spin correlations in quantum materials.
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