arXiv subjects

Junrong Wang

Publications and source records attributed to Junrong Wang.

4 recordsLinked to original sources

arXiv2025

Phase-controlled quantum transport signatures in a quantum dot-Majorana hybrid ring system

We investigate the quantum transport in a hybrid ring system consisting of a quantum dot (QD) coupled to two Majorana bound states (MBSs) hosted in a topological superconducting nanowire, threaded by a magnetic flux. Utilizing the dissipaton equation-of-motion approach, we demonstrate that the differential conductance shows periodic behavior and its periodicity depends on both the QD energy level and the MBS overlapping. A zero-bias peak (ZBP) emerges as a result of the balance between normal and anomalous tunneling processes, associated with the presence of a single MBS. Beyond the phase-dependent periodic behavior, the shot noise exhibits voltage-dependent transitions between sub-Poissonian ($F = 0.5$), Poissonian ($F = 1$), and super-Poissonian ($F > 1$) regimes. Strikingly, we find a giant Fano factor ($F\gg1$) emerging at the balance point, accompanied by a peak in the shot noise. This distinctive feature may serve as a supplementary signature for MBS detection. However, both ZBP in the differential conductance and shot noise peak are degraded by thermal effects.

cond-mat.mes-hall↗

arXiv2025

Distinguishing Majorana bound states from Andreev bound states through differential conductance and current noise spectrum

We investigate the quantum transport through a quantum dot coupled with a superconducting (SC) nanowire. By elaborating the differential conductance and current noise spectrum, we focus on the distinct characteristics of the topological Majorana bound states (MBSs) and trivial Andereev bound states (ABSs) hosted in SC wire. For MBSs with a topological quality factor $q=1$, we observe the degenerate features manifested as the zero-bias peak (ZBP) in differential conductance and the Rabi dips degeneracy (RDD) in noise spectrum. In contrast, for ABSs with $q<1$, the splitting of these degenerate features depends on the linewidth, arising from realistic measurement conditions. Furthermore, we identify the critical quality factors $q_{\rm c}$ and $q_{\rm s}$ associated with the emergences of ZBP and RDD, respectively. The value of $q_{\rm c}$ is temperature-dependent, and we establish a suitable temperature window to ensure the visibility of single ZBP in the experiments. Whereas, $q_{\rm c}$ depends on the coupling strength rather than the temperature. Typical values for these quality factors are approximately $q_{\rm c}\approx 0.93$ and $q_{\rm s}\approx 0.99$. Our results suggest that the degenerate Rabi spectrum signal could serve as a hallmark for the presence of MBSs, which goes beyond the scope of differential conductance.

cond-mat.mes-hall↗

arXiv2024

Bubble dynamics in the Polyakov quark-meson model

In the framework of the Polyakov quark-meson model with two flavors, the bubble dynamics of a first-order phase transition in the region of high density and low temperature are investigated by using the homogeneous thermal nucleation theory. In mean-field approximation, after obtaining the effective potential with inclusion of the fermionic vacuum term, we build a geometric method to search two existing minima, which can be actually connected by a bounce interpolated between a local minimum to an adjacent global one. For both weak and strong first-order hadron quark phase transitions, as fixing the chemical potentials at $μ=306 \mathrm{MeV}$ and $μ=310 \mathrm{MeV}$, the bubble profiles, the surface tension, the typical radius of the bounce and the saddle point action as a function of temperature are numerically calculated in the presence of a nucleation bubble. It is found that the surface tension remains a very small value even when the density is high. It is also noticed that the deconfinement phase transition does not change chiral phase transition dramatically for light quarks and phase boundaries for hadron and quark matter should be resized properly according to the saddle-point action evaluated on the bounce solution.

hep-ph↗

arXiv2024

Bubble nucleation in the two-flavor quark-meson model

We investigate the dynamics of a first-order quark-hadron transition via homogeneous thermal nucleation in the two-flavor quark-meson model. The contribution of the fermionic vacuum loop in the effective thermodynamics potential and phase diagram together with the location of critical end point (CEP) have been obtained in the temperature and chemical potential plane. For a weak and strong first-order phase transition, by taking the temperature as a variable, the critical bubble profiles, the evolutions of the surface tension and the saddle-point action in the presence of a nucleation bubble are numerically calculated in detail when fixing the chemical potentials at $μ=306 \mathrm{MeV}$ and $μ=309 \mathrm{MeV}$. Our results show that the system could be trapped in the metastable state for a long time as long as the temperature is between the metastable region characterized by the up and low spinodal lines. Moreover, the surface tension at criticality will rise up to about $4 \mathrm{MeV/fm^2}$ when the chemical potential is very high. Such a small value of the surface tension would favor a mixed phase in the cores of compact stars and may have an important implication in astrophysics.

hep-ph↗