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Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling.

Wang C, Ren J, Cao J - Sci Rep (2015)

Bottom Line: Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime.The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity.The results will have broad implications for the fine control of energy transfer in nano-structural devices.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA [2] Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602, Singapore [3] Department of Physics, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China.

ABSTRACT
Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices.

No MeSH data available.


Related in: MedlinePlus

The energy flux and quantum coherence represented by 〈σx〉, as functions of the coupling strength.The solid black line is from the NE-PTRE, which unifies the Redfield result at the weak coupling (the red dashed line) and the NIBA result at the strong coupling (the dot-dashed blue line). The deviation of the unified energy flux from the NIBA result at small α is characterized by the quantum coherence  (inset). Parameters are given by ε0 = 0, Δ = 5.22 meV, ωc = 26.1 meV, TL = 150 K and TR = 90 K.
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f3: The energy flux and quantum coherence represented by 〈σx〉, as functions of the coupling strength.The solid black line is from the NE-PTRE, which unifies the Redfield result at the weak coupling (the red dashed line) and the NIBA result at the strong coupling (the dot-dashed blue line). The deviation of the unified energy flux from the NIBA result at small α is characterized by the quantum coherence (inset). Parameters are given by ε0 = 0, Δ = 5.22 meV, ωc = 26.1 meV, TL = 150 K and TR = 90 K.

Mentions: Next, we plot the energy flux of Eq. (10) in Fig. 3, which first shows linear increase with the system-bath coupling at weak regime, consistent with the Redfield. After reaching a maximum, the energy flux decreases monotonically in the strong coupling regime, of which the profile coincide with the NIBA. The discrepancy of the NIBA and our NE-PTRE is due to the improper ignorance of quantum coherence of the TLS in NIBA (see also Eq. (2), in which the term containing σx is absent in the NIBA method). This coherence term describes the effective tunneling within TLS so that it enhances the energy transfer compared to the NIBA that ignores it.


Nonequilibrium Energy Transfer at Nanoscale: A Unified Theory from Weak to Strong Coupling.

Wang C, Ren J, Cao J - Sci Rep (2015)

The energy flux and quantum coherence represented by 〈σx〉, as functions of the coupling strength.The solid black line is from the NE-PTRE, which unifies the Redfield result at the weak coupling (the red dashed line) and the NIBA result at the strong coupling (the dot-dashed blue line). The deviation of the unified energy flux from the NIBA result at small α is characterized by the quantum coherence  (inset). Parameters are given by ε0 = 0, Δ = 5.22 meV, ωc = 26.1 meV, TL = 150 K and TR = 90 K.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4495559&req=5

f3: The energy flux and quantum coherence represented by 〈σx〉, as functions of the coupling strength.The solid black line is from the NE-PTRE, which unifies the Redfield result at the weak coupling (the red dashed line) and the NIBA result at the strong coupling (the dot-dashed blue line). The deviation of the unified energy flux from the NIBA result at small α is characterized by the quantum coherence (inset). Parameters are given by ε0 = 0, Δ = 5.22 meV, ωc = 26.1 meV, TL = 150 K and TR = 90 K.
Mentions: Next, we plot the energy flux of Eq. (10) in Fig. 3, which first shows linear increase with the system-bath coupling at weak regime, consistent with the Redfield. After reaching a maximum, the energy flux decreases monotonically in the strong coupling regime, of which the profile coincide with the NIBA. The discrepancy of the NIBA and our NE-PTRE is due to the improper ignorance of quantum coherence of the TLS in NIBA (see also Eq. (2), in which the term containing σx is absent in the NIBA method). This coherence term describes the effective tunneling within TLS so that it enhances the energy transfer compared to the NIBA that ignores it.

Bottom Line: Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime.The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity.The results will have broad implications for the fine control of energy transfer in nano-structural devices.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA [2] Singapore-MIT Alliance for Research and Technology, 1 CREATE Way, Singapore 138602, Singapore [3] Department of Physics, Hangzhou Dianzi University, Hangzhou, Zhejiang 310018, China.

ABSTRACT
Unraveling the microscopic mechanism of quantum energy transfer across two-level systems provides crucial insights to the optimal design and potential applications of low-dimensional nanodevices. Here, we study the non-equilibrium spin-boson model as a minimal prototype and develop a fluctuation-decoupled quantum master equation approach that is valid ranging from the weak to the strong system-bath coupling regime. The exact expression of energy flux is analytically established, which dissects the energy transfer as multiple boson processes with even and odd parity. Our analysis provides a unified interpretation of several observations, including coherence-enhanced heat flux and negative differential thermal conductance. The results will have broad implications for the fine control of energy transfer in nano-structural devices.

No MeSH data available.


Related in: MedlinePlus