Nagaoka ferromagnetism observed in a quantum dot plaquette

Engineered, highly controllable quantum systems are promising simulators of emergent physics beyond the simulation capabilities of classical computers¹. An important problem in many-body physics is itinerant magnetism, which originates purely from long-range interactions of free electrons and whose existence in real systems has...

Interaction without back action in the context of quantum manipulation

We address the interaction between two quantum systems (A and B) that is mediated by their common linear environment. If the environment is out of equilibrium, the resulting interaction violates Onsager relations and cannot be described by a Hamiltonian. In simple terms, the action of system A on system B does not necessarily produce a back...

Nonlinear and dot-dependent Zeeman splitting in GaAs/AlGaAs quantum dot arrays

We study the Zeeman splitting in lateral quantum dots that are defined in GaAs-AlGaAs heterostructures by means of split gates. We demonstrate a nonlinear dependence of the splitting on magnetic field and its substantial variations from dot to dot and from heterostructure to heterostructure. These phenomena are important in the context of...

Finite-Temperature Disordered Bosons in Two Dimensions

We study phase transitions in a two dimensional weakly interacting Bose gas in a random potential at finite temperatures. We identify superfluid, normal fluid, and insulator phases and construct the phase diagram. At T=0 one has a tricritical point where the three phases coexist. The truncation of the energy distribution at the trap barrier,...