scholarly journals Quantum Ising chain with boundary dephasing

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Naoyuki Shibata ◽  
Hosho Katsura
Keyword(s):  
Hilbert Space ◽  
Relaxation Time ◽  
Chemical Potential ◽  
System Size ◽  
Ising Chain ◽  
Inverse Relaxation Time

Abstract We study the quantum Ising chain with boundary dephasing. By doubling the Hilbert space, the model is mapped to the Su–Schrieffer–Heeger model with imaginary chemical potential at the edges. We show analytically and numerically that the Liouvillian gap, i.e. the inverse relaxation time of the model, scales with the system size $ N $ as $ N^{-3} $.

scholarly journals Research on Perfect and Tunable Metamaterial Absorber Based on Crosshair-shaped Graphene

2021 ◽  
Vol 2109 (1) ◽  
pp. 012015
Author(s):  
Yiran Guo ◽  
Yunping Qi ◽  
Chuqin Liu ◽  
Weiming Liu ◽  
Xiangxian Wang
Keyword(s):  
Relaxation Time ◽  
Chemical Potential ◽  
Incident Angle ◽  
Fdtd Method ◽  
Reference Value ◽  
Metamaterial Absorber ◽  
Selective Absorption ◽  
Perfect Absorber ◽  
Wide Angle ◽  
Perfect Absorption

Abstract Graphene, as a new nano-material, according to the physical properties of electric field localization and selective absorption on light of surface plasmon resonance (SPR), a tunable, multi-band and wide-angle perfect absorber based on crosshair-shaped graphene is devised by using the Finite Difference in Time Domain (FDTD) method. In this paper, the effects of chemical potential, relaxation time, and incident angle of light on the absorptivity of graphene are systematically discussed. The simulation experiment shows that there are two absorption peaks with perfect absorption rate appeared in the study range, and the maximum modulation index can be obtained by changing the relaxation time. Finally, it proves that the absorber is insensitive to wide-angle of light. Thus, it is able to be concluded that the absorber has a great reference value to sensor, wireless communication, biomedical and other fields.

Graphene-based microwave coaxial antenna for microwave ablation: thermal analysis

2020 ◽  
pp. 1-9
Author(s):  
Burak Uzman ◽  
Adem Yilmaz ◽  
Hulusi Acikgoz ◽  
Raj Mittra
Keyword(s):  
Relaxation Time ◽  
Microwave Ablation ◽  
Graphene Layer ◽  
Heat Dissipation ◽  
Chemical Potential ◽  
Treatment Time ◽  
Slot Antenna ◽  
Necrotic Tissue ◽  
Cancerous Tissue ◽  
High Impedance

Abstract In this study, the problem of backward heating in microwave ablation technique is examined and an electromagnetic solution based on the use of high impedance graphene material is presented for its mitigation. In this context, a one-atom-thick graphene layer is added on the coaxial double slot antenna. In addition to the electromagnetic behavior, thermal effects caused by the graphene-covered antenna are emphasized. The graphene's conductivity being highly dependent on its chemical potential and the relaxation time, a parametric study is performed to determine a range of tolerances within which the graphene-coated antenna outperform a typical graphene-free antenna. The range of values is found to be 0 < μ c < 0.5 eV and τ < 0.4 ps, for the chemical potential and the relaxation time, respectively. The backward heating problem being prevented, the ablation region is ensured to be spherical around the tip of the antenna. Effects of the graphene layer to the heat dissipation in the tissue, the necrotic tissue ratio (damage to the cancerous tissue of the caused by electromagnetic energy), and the treatment time using the coaxial double slot antenna were examined. The results show that the heat dissipation is concentrated around the slots (region of cancerous tissue) and a higher necrotic tissue ratio can be achieved with a graphene-covered double slot antenna in a shorter time.

scholarly journals Finite-volume effects on phase transition in the Polyakov-loop extended Nambu–Jona-Lasinio model with a chiral chemical potential

2017 ◽  
Vol 32 (13) ◽  
pp. 1750067 ◽  
Author(s):  
Zan Pan ◽  
Zhu-Fang Cui ◽  
Chao-Hsi Chang ◽  
Hong-Shi Zong
Keyword(s):  
Finite Volume ◽  
Chemical Potential ◽  
System Size ◽  
Heavy Ion ◽  
Polyakov Loop ◽  
End Point ◽  
Chemical Potentials ◽  
Ion Collision ◽  
Quark Flavors ◽  
Volume Effects

To investigate the finite-volume effects on the chiral symmetry restoration and the deconfinement transition for a quantum chromodynamics (QCD) system with [Formula: see text] (two quark flavors), we apply the Polyakov-loop extended Nambu–Jona-Lasinio model by introducing a chiral chemical potential [Formula: see text] artificially. The final numerical results indicate that the introduced chiral chemical potential does not change the critical exponents, but shifts the location of critical end point (CEP) significantly; the ratios for the chiral chemical potentials and temperatures at CEP, [Formula: see text] and [Formula: see text], are significantly affected by the system size [Formula: see text]. The behavior is that [Formula: see text] increases slowly with [Formula: see text] when [Formula: see text] is “large” and [Formula: see text] decreases first and then increases with [Formula: see text] when [Formula: see text] is “small.” It is also found that for a fixed [Formula: see text], there is a [Formula: see text], where the critical end point vanishes and the whole phase diagram becomes a crossover when [Formula: see text]. Therefore, we suggest that for the heavy-ion collision experiments, which is to study the possible location of CEP, the finite-volume behavior should be taken into account.

scholarly journals Persistent dark states in anisotropic central spin models

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tamiro Villazon ◽  
Pieter W. Claeys ◽  
Mohit Pandey ◽  
Anatoli Polkovnikov ◽  
Anushya Chandran
Keyword(s):  
Relaxation Time ◽  
Solid State ◽  
Quantum Dot ◽  
Large Deviations ◽  
Thermal Equilibrium ◽  
Relaxation Times ◽  
System Size ◽  
Small Perturbations ◽  
Spin Models ◽  
Spin Bath

Abstract Long-lived dark states, in which an experimentally accessible qubit is not in thermal equilibrium with a surrounding spin bath, are pervasive in solid-state systems. We explain the ubiquity of dark states in a large class of inhomogeneous central spin models using the proximity to integrable lines with exact dark eigenstates. At numerically accessible sizes, dark states persist as eigenstates at large deviations from integrability, and the qubit retains memory of its initial polarization at long times. Although the eigenstates of the system are chaotic, exhibiting exponential sensitivity to small perturbations, they do not satisfy the eigenstate thermalization hypothesis. Rather, we predict long relaxation times that increase exponentially with system size. We propose that this intermediate chaotic but non-ergodic regime characterizes mesoscopic quantum dot and diamond defect systems, as we see no numerical tendency towards conventional thermalization with a finite relaxation time.

scholarly journals TERAHERTZ GRAPHENE PLASMON SINGLE REFLECTARRAY MODULE MODELING

2019 ◽  
Vol 9 ◽  
pp. 66-71
Author(s):  
Alexander Cherevko ◽  
Yury Morgachev
Keyword(s):  
Relaxation Time ◽  
Chemical Potential

Simulation of a plasmon single graphene reflectarray module operating at a frequency of 1.35 THz is presented. The dependences of the characteristics of a plasmon single graphene reflectarray module on changes in various parameters of graphene (temperature, chemical potential and relaxation time) are considered.

scholarly journals The nonequilibrium quantum many-body problem as a paradigm for extreme data science

2014 ◽  
Vol 28 (31) ◽  
pp. 1430021 ◽  
Author(s):  
J. K. Freericks ◽  
B. K. Nikolić ◽  
O. Frieder
Keyword(s):  
Hilbert Space ◽  
Big Data ◽  
Computer Science ◽  
Computational Methods ◽  
Data Science ◽  
Body Problem ◽  
System Size ◽  
Many Body ◽  
Data Set ◽  
New Approaches

Generating big data pervades much of physics. But some problems, which we call extreme data problems, are too large to be treated within big data science. The nonequilibrium quantum many-body problem on a lattice is just such a problem, where the Hilbert space grows exponentially with system size and rapidly becomes too large to fit on any computer (and can be effectively thought of as an infinite-sized data set). Nevertheless, much progress has been made with computational methods on this problem, which serve as a paradigm for how one can approach and attack extreme data problems. In addition, viewing these physics problems from a computer-science perspective leads to new approaches that can be tried to solve more accurately and for longer times. We review a number of these different ideas here.

scholarly journals Universal Constraints on Relaxation Times for d-Level GKLS Master Equations

2017 ◽  
Vol 24 (04) ◽  
pp. 1740009
Author(s):  
Gen Kimura ◽  
Shigeru Ajisaka ◽  
Kyouhei Watanabe
Keyword(s):  
Relaxation Time ◽  
Relaxation Rate ◽  
Master Equation ◽  
Experimental Test ◽  
Relaxation Times ◽  
Master Equations ◽  
Complete Positivity ◽  
Relaxation Rates ◽  
Markovian Dynamics ◽  
Inverse Relaxation Time

In 1976, Gorini, Kossakowski, Sudarshan and Lindblad independently discovered a general form of master equations for an open quantum Markovian dynamics. In honor of all the authors, the equation is nowadays called the GKLS master equation. In this paper, we show universal constraints on the relaxation times valid for any d-level GKLS master equations, which is a generalization of the well-known constraints for 2-level systems. Specifically, we show that any relaxation rate, the inverse-relaxation time, is not greater than half of the sum of all relaxation rates. Since the relaxation times are measurable in experiments, our constraints provide a direct experimental test for the validity of the GKLS master equations, and hence for the conditions of the complete positivity and Markovianity.

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