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Quantum magnets under pressure: controlling elementary excitations in TlCuCl3
Ch Rüegg1, B Normand, M Matsumoto
1London Centre for Nanotechnology, University College London, London WC1E 6BT, United Kingdom.
Physical Review Letters
|June 4, 2008
Summary
We studied quantum critical points in TlCuCl3 using neutron spectroscopy. A new massive excitation emerged, revealing quantum effects beyond classical magnetism.
Area of Science:
- Condensed Matter Physics
- Quantum Magnetism
Background:
- TlCuCl3 exhibits a quantum disordered phase and long-ranged magnetic order.
- Quantum critical points (QCPs) are boundaries between distinct quantum phases.
Purpose of the Study:
- To investigate elementary excitations in TlCuCl3 across a pressure-induced QCP.
- To understand the emergence of new excitations at the QCP.
Main Methods:
- Neutron spectroscopy was employed to probe magnetic excitations.
- Pressure was applied to tune the material through its QCP.
Main Results:
- A low-lying, massive excitation was observed in the weakly ordered phase.
- This excitation corresponds to longitudinal magnetic moment fluctuations.
- The excitation is absent in classical magnetic descriptions.
Conclusions:
- The observed excitation is a direct consequence of the quantum critical point.
- This finding highlights the unique nature of excitations at quantum phase transitions.
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