We study the influence of quenched disorder on quantum phase transitions in systems with overdamped dynamics. For Ising order-parameter symmetry disorder destroys the sharp phase transition by rounding because a static order parameter can develop on rare spatial regions. This leads to an exponential dependence of the order parameter on the coupling constant. At finite temperatures the static order on the rare regions is destroyed. This restores the phase transition and leads to a double exponential relation between critical temperature and coupling strength. We discuss the behavior based on Lifshitz-tail arguments and illustrate the results by simulations of a model system.
T. Vojta, "Disorder-Induced Rounding of Certain Quantum Phase Transitions," Physical Review Letters, vol. 90, no. 10, pp. 107202/1-107202/4, American Physical Society (APS), Mar 2003.
The definitive version is available at http://dx.doi.org/10.1103/PhysRevLett.90.107202
Keywords and Phrases
Asymptotic stability; Electrons; Ferromagnetic materials; Hamiltonians; Magnetic susceptibility; Magnetization; Mathematical models; Quantum theory; Temperature; Disorder induced rounding; Finite size scaling; Ising order parameter symmetry disorder; Quantum phase transitions
International Standard Serial Number (ISSN)
Article - Journal
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