Engineering topics

Chien, Chih-Chun

Publications and source records attributed to Chien, Chih-Chun.

3 records

DOE OSTI2022

Custodial Chiral Symmetry in a Su-Schrieffer-Heeger Electrical Circuit with Memory

Custodial symmetries are common in the standard model of particle physics. They arise when quantum corrections to a parameter are proportional to the parameter itself. Here, we show that a custodial symmetry of the chiral type is also present in a classical Su-Schrieffer-Heeger (SSH) electrical circuit with memory. In the absence of memory, the SSH circuit supports a symmetry-protected topological edge state. Memory induces nonlinearities that break chiral symmetry explicitly and spread the state across the circuit. However, the resulting state is still protected against perturbations by the ensuing custodial chiral symmetry. Furthermore, these predictions can be verified experimentally and demonstrate the interplay between symmetry and memory.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2019

Reentrant Fulde-Ferrell-Larkin-Ovchinnikov state in small-sized superconductors

We study the effect of a parallel magnetic field in a thin and small superconductor. The field suppresses superconductivity through Zeeman coupling while stabilizing the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state at high fields before superconductivity is destroyed. When the spatial period of FFLO state is comparable to the size of the superconductor, there is a strong commensuration effect, which modifies the superconducting phase diagram. We investigate the FFLO state and the phase diagram in the presence of strong commensuration effect both for the s-and d-wave superconductors using the Bogoliubov–de Gennes equation, Green function approach, and Ginzburg-Landau theory. Here, we found that the superconducting phase diagram is strongly modulated. Interestingly, there is reentrance of superconductivity upon increasing the magnetic field. The commensuration effect of the FFLO state can be used to detect the FFLO state in experiments.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Tunable current circulation in triangular quantum-dot metastructures

Advances in fabrication and control of quantum dots allow the realization of metastructures that may exhibit novel electrical transport phenomena. In this work, we investigate the electrical current passing through one such metastructure, a system composed of quantum dots placed at the vertices of a triangle. The wave nature of quantum particles leads to internal current circulation within the metastructure in the absence of any external magnetic field. We uncover the relation between the metastructure steady-state total current and the internal circulation. By calculating the electronic correlations in quantum transport exactly, we present phase diagrams showing where different types of current circulation can be found as a function of the correlation strength and the coupling between the quantum dots. Finally, we show that the regimes of current circulation can be further enhanced or reduced depending on the local spatial distribution of the interactions, suggesting a single-particle scattering mechanism is at play even in the strongly correlated regime. We suggest experimental realizations of actual quantum-dot metastructures where our predictions can be directly tested.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗