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Quantum Phase Transitions and Conserved Charges

Subir Sachdev
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Abstract

The constraints on the scaling properties of conserved charge densities in the vicinity of a zero temperature ($T$), second-order quantum phase transition are studied. We introduce a generalized Wilson ratio, characterizing the non-linear response to an external field, $H$, coupling to any conserved charge, and argue that it is a completely universal function of $H/T$: this is illustrated by computations on model systems. We also note implications for transitions where the order parameter is a conserved charge (as in a $T=0$ ferromagnet-paramagnet transition).

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Subir Sachdev. 1993-12-04. Quantum Phase Transitions and Conserved Charges. https://doi.org/10.1007/bf01317409

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