Unveiling the quantum critical point of an Ising chain

Shiyan Li

Fudan University, Shanghai, China


    Quantum phase transitions occur at zero temperature upon variation of some nonthermal control parameters. The Ising chain in a transverse field is probably the most-studied model undergoing such a transition, from ferromagnetic to paramagnetic state. This model can be exactly solved by using a Jordan-Wigner transformation, which transforms the spins into noninteracting spinless fermions. At the quantum critical point, the magnetic excitations can carry arbitrarily low energy and dominate the low temperature properties. I will report the unveiling of such quantum critical point in quasi-one-dimensional Ising ferromagnet CoNb2O6 by ultra-low-temperature thermal conductivity measurements. I will also briefly report a related work, the observation of spinon Anderson localization in a spin-1/2 antiferromagnetic Heisenberg chain by thermal conductivity measurements.

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