Non-equilibrium quantum mechanics: A 'hot quantum soup' of paramagnons

Abstract

Motivated by recent measurements of the lifetime (decay width) of paramagnons in quantum antiferromagnet TlCuCl3, we investigate paramagnon decay in a heat bath and formulate an appropriate quantum theory. Our formulation can be split into two regimes: (i) a non-perturbative, 'hot quantum soup' regime where paramagnon width is comparable to its energy; (ii) usual perturbative regime where paramagnon width is significantly lower than its energy. Close to the Neel tempera- ture the paramagnon width becomes comparable to its energy and falls into the hot quantum soup regime. To describe this regime we develop a new finite frequency, finite temperature technique for a nonlinear quantum field theory; the 'golden rule of quantum kinetics'. The formulation is generic and applicable to any three dimensional quantum antiferromagnet in the vicinity of a quantum critical point. Specifically we apply our results to TlCuCl3 and find agreement with experimental data. Additionally, we show that logarithmic running of the coupling constant in the upper critical dimension changes the commonly accepted picture of the quantum disordered and quantum critical regimes.

References in corpus (7)

• Spontaneous Magnon Decays
• Quantum Magnets under Pressure: Controlling Elementary Excitations in TlCuCl3
• Quantum and classical criticality in a dimerized quantum antiferromagnet
• Field-induced decay dynamics in square-lattice antiferromagnet
• Multiplicative logarithmic corrections to quantum criticality in three-dimensional dimerized antiferromagnets
• Asymptotic Freedom in Quantum Antiferromagnet TlCuCl3
• Spectral function of the Higgs mode in 4-\varepsilon dimensions

Cited by in corpus (10)

• General Markovian Equation for Scalar Fields in a Slowly Evolving Background
• Universal scalings of Néel temperature, staggered magnetization density, and spinwave velocity of three-dimensional disordered and clean quantum antiferromagnets
• Classification for the universal scaling of Néel temperature and staggered magnetization density of three-dimensional dimerized spin-1/2 antiferromagnets
• Unifying static and dynamic properties in 3D quantum antiferromagnets
• Stable high-temperature paramagnons in a three-dimensional antiferromagnet near quantum criticality: Application to TlCuCl${}_3$
• Pressure-tuned quantum criticality in the large-$D$ antiferromagnet DTN
• Quantum Lifshitz criticality in a frustrated two-dimensional XY model
• Universal scaling of three-dimensional dimerized quantum antiferromagnets on bipartite lattices
• Quantum critical dynamics for a prototype class of insulating antiferromagnets
• Anomalous thermal broadening from an infrared catastrophe in two-dimensional quantum antiferromagnets