Andrew Smerald, Nic Shannon
The idea that a quantum system could behave like a liquid crystal holds a longstanding fascination. One widely-discussed example is the quantum spin-nematic, in which magnetic moments order as spin-quadrupoles, breaking spin-rotation symmetry without breaking time-reversal symmetry. However, despite a long history, experimental evidence for the existence of the spin-nematic state remains scarce. Here we show how the NMR 1/T_1 relaxation rate can be used to distinguish the spin-nematic state from more conventional forms of magnetic order. Building on a symmetry-based theory of spin excitations, we find that, in a spin-nematic phase, 1/T_1 is dramatically suppressed, does not diverge at continuous phase transitions, and exhibits unconventional power laws at low temperatures. We discuss how this theory could be applied to LiCuVO_4, where spin-nematic order has been proposed to exist at high magnetic field.
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http://arxiv.org/abs/1303.4465
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