Autor: |
Fillaux, François, Cousson, Alain, Gutmann, Matthias J. |
Rok vydání: |
2008 |
Předmět: |
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Zdroj: |
Journal of Physics Condensed Matter 20 (2007) 015225 |
Druh dokumentu: |
Working Paper |
DOI: |
10.1088/0953-8984/20/01/015225 |
Popis: |
We utilize single-crystal neutron diffraction to study the $C2/m$ structure of potassium hydrogen carbonate (KHCO$_3$) and macroscopic quantum entanglement above the phase transition at $T_c = 318$ K. Whereas split atom sites could be due to disorder, the diffraction pattern at 340 K evidences macroscopic proton states identical to those previously observed below $T_c$ by F. Fillaux et al., (2006 \textit{J. Phys.: Condens. Matter} \textbf{18} 3229). We propose a theoretical framework for decoherence-free proton states and the calculated differential cross-section accords with observations. The structural transition occurs from one ordered $P2_1/a$ structure ($T < T_c$) to another ordered $C2/m$ structure. There is no breakdown of the quantum regime. It is suggested that the crystal is a macroscopic quantum object which can be represented by a state vector. Raman spectroscopy and quasi-elastic neutron scattering suggest that the $|C2/m>$ state vector is a superposition of the state vectors for two $P2_1/a$-like structures symmetric with respect to $(a,c)$ planes. |
Databáze: |
arXiv |
Externí odkaz: |
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