Interaction induced topological phase transition in Bernevig-Hughes-Zhang model

We study interaction induced topological phase transition in Bernevig-Hughes-Zhang model. Topological nature of the phase transition is revealed by directly calculating the Z2 index of the interacting system from the single-particle Green's function. The interacting Z2 index is also consistently checked through the edge spectra. Combined with ab initio methods, present approach is a useful tool searching for correlated topological insulating materials from the first-principle point of view.Comment: 4.5 pages, 4 figures, reference adde

Transport equation for 2D electron liquid under microwave radiation plus magnetic field and the Zero Resistance State

A general transport equation for the center of mass motion is constructed to study transports of electronic system under uniform magnetic field and microwave radiation. The equation is applied to study 2D electron system in the limit of weak disorder where negative resistance instability is observed when the radiation field is strong enough. A solution of the transport equation with spontaneous AC current is proposed to explain the experimentally observed Radiation-Induced Zero Resistance State.Comment: 9 pages, 1 figur

Alternative Functionals Estimation Based on Index Models and Kernel Approach

Treballs Finals del Màster de Ciències Actuarials i Financeres, Facultat d'Economia i Empresa, Universitat de Barcelona, Curs: 2023-2024, Tutoria: Catalina Bolancé LosillaThis work explores the utilization of double cross-validation methods for determining the optimal bandwidth in kernel regression using single index-models. Kernel regression is a non-parametric technique widely employed in various fields, particularly in smoothing noisy data. The bandwidth parameter plays a crucial role in kernel regression, controlling the smoothness of the estimated function. Selecting an appropriate bandwidth is essential for achieving accurate and robust model performance. Traditional approaches to band- width selection often rely on heuristic methods or fixed rules, which may not be optimal for all datasets (...

Pole expansion of self-energy and interaction effect on topological insulators

We study effect of interactions on time-reversal-invariant topological insulators. Their topological indices are expressed by interacting Green's functions. Under the local self-energy approximation, we connect topological index and surface states of an interacting system to an auxiliary noninteracting system, whose Hamiltonian is related to the pole-expansions of the local self-energy. This finding greatly simplifies the calculation of interacting topological indices and gives an noninteracting pictorial description of interaction driven topological phase transitions. Our results also bridge studies of the correlated topological insulating materials with the practical dynamical-mean-field-theory calculations.Comment: 4.2 pages, 3 figures, reference added, typos correcte