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Seminário de Física da Matéria Condensada

Palestrante: Tobias Micklitz (CBPF)

title: Disordered Quantum Systems from Anderson- to many-body localization

Disorder is known to have dramatic effects on single particle-dynamics in low dimensional quantum systems. The absence of diffusion in dimensions smaller than three emerges within a single-particle picture where non-interacting particles, scattering off disorder, interfere with themselves and effectively get localized to a finite region in space. This ‘Anderson localization’ originates from the quantum-mechanical wave-nature of particles and is fundamentally different from classical trapping in deep valleys of a disorder potential. The impact of weak interactions on the single-particle localization problem can be subsumed as a fluctuating bath. The bath induces decoherence and thus suppresses localization. More strikingly, it has been recently proposed that (isolated) disordered quantum systems of interacting particles undergo a finite-temperature phase-transition which can be thought of as a many-body localization transition. The ‘many-body localized’ phase is characterized by the absence of ergodicity and the vanishing of transport coefficients. In the talk I will give a brief introduction into the phenomenon of (quantum) localization in disordered systems emphasizing recent trends, and then discuss a field-theory approach to the many-body localization problem.