Superfluid density in continuous and discrete spaces: Avoiding misconceptions

  title={Superfluid density in continuous and discrete spaces: Avoiding misconceptions},
  author={V. G. Rousseau},
  journal={Physical Review B},
We review the concept of superfluidity and, based on real and thought experiments, we use the formalism of second quantization to derive expressions that allow the calculation of the superfluid density for general Hamiltonians with path-integral methods. It is well known that the superfluid density can be related to the response of the free energy to a boundary phase-twist, or to the fluctuations of the winding number. However, we show that this is true only for a particular class of… Expand
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