Fluctuation-induced First Order Quantum Phase Transition of U(1) Quantum Spin Liquid in Pyrochlore Quantum Antiferromagnet

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We show using quantum free energy calculation that the quantum phase transition between U(1) quantum spin liquid (QSL) and antiferromagnet (AFM) phases in pyrochlore quantum antiferromagnet (QAFM) is a first order rather than second order. This change in order from second to first order is induced by gauge fluctuations, which are explicitly taken into account at gauge theory level in our effective low energy theory. We therefore have discovered a fluctuation-induced first order quantum phase transition in pyrochlore QAFM. We explicitly derive the quantum free energy description of this QSL to AFM phase transition and show that it is a weakly first order phase transition. We also briefly discuss the experimental relevance of this result.