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Cornell University
LASSP -  Laboratory of Atomic and Solid State Physics

Cornell Laboratory for Atomic and Solid State Physics

Eun-Ah Kim group finds new insights to entanglement entropy

Eun-Ah Kim's group reported in May 22 issue of Physical Review Letters that the poster child non-Fermi liquid state found at filling factor ν = ½ shows strongly enhanced quantum entanglement as a result of strong correlations in the system. The ν = ½ composite fermion non-Fermi liquid state occurs when extremely clean two dimensional electron gas is subject under magnetic field such that there are two flux quanta per electron. This state has long been viewed as a prototypical example of fermions coupled to emergent gauge field which mediates strong interaction. However the state does not show any broken symmetry and hence cannot be described using conventional order parameter formalism. Kim group and collaborators used state of art numerical scheme to calculate the bi-partite entanglement entropy which measures the quantum mechanical entanglement between a sub-region and the rest of the system. They report two unforeseen aspects: 1) there is no change in the scaling of the entaglement 2) the scaling factor which counts number of free channels for free fermions is greatly enhanced. The results can be found at:

 Entanglement entropy scaling