Ryan Requist

Pier Paolo Baruselli; Ryan Requist; Michele Fabrizio; Erio Tosatti

A simple device of three laterally coupled quantum dots, the central one contacted by metal leads, provides a realization of the ferromagnetic Kondo model, which is characterized by interesting properties like a nonanalytic inverted zero-bias anomaly and an extreme sensitivity to a magnetic field. Tuning the gate voltages of the lateral dots allows us to study the transition from a ferromagnetic to antiferromagnetic Kondo effect, a simple case of a Berezinskii-Kosterlitz-Thouless transition. We model the device by three coupled Anderson impurities that we study by numerical renormalization group. We calculate the single-particle spectral function of the central dot, which at zero frequency is proportional to the zero-bias conductance, across the transition, both in the absence and in the presence of a magnetic field.

Ryan Requist; Falk Tandetzky; E. K. U. Gross

The Born-Oppenheimer electronic wave function

Pier Paolo Baruselli; Ryan Requist; Alexander Smogunov; Michele Fabrizio; Erio Tosatti

{\mathrm{\ensuremath{\Phi}}}_{R}^{\text{BO}}(r)

Ryan Requist; P. M. Sheverdyaeva; Paolo Moras; Sanjoy K. Mahatha; C. Carbone; Erio Tosatti

picks up a topological phase factor

Ryan Requist; John Schliemann; Alexander G. Abanov; Daniel Loss

\ifmmode\pm\else\textpm\fi{}1

Ryan Requist

, a special case of Berry phase, when it is transported around a conical intersection of two adiabatic potential energy surfaces in

Ryan Requist; Cesar R. Proetto; E. K. U. Gross

R

Pier Paolo Baruselli; Michele Fabrizio; Alexander Smogunov; Ryan Requist; Erio Tosatti

space. We show that this topological quantity reverts to a geometric quantity

Chen Li; Ryan Requist; E. K. U. Gross

{e}^{i\ensuremath{\gamma}}

P. M. Sheverdyaeva; Ryan Requist; Paolo Moras; Sanjoy K. Mahatha; M. Papagno; L. Ferrari; Erio Tosatti; C. Carbone

if the geometric phase