Dissipative tunneling in nanosystems

Journal Article · Sat Oct 15 04:00:00 EDT 2011 · Journal of Experimental and Theoretical Physics

DOI:https://doi.org/10.1134/S1063776111090032· OSTI ID:22028010

Benderskii, V A ^[1]

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1. Russian Academy of Sciences, Institute of Problems of Chemical Physics (Russian Federation)

A quantum dynamical problem has been analytically solved for a two-level system where localized states L{sub 0} and R{sub 0} are strongly coupled with reservoirs of local oscillations {l_brace}L{sub n}{r_brace} and {l_brace}R{sub n}{r_brace}. It is additionally assumed that the spectra of reservoirs are equidistant and the coupling constants are the same. It has been shown that the evolution of states L{sub 0} and R{sub 0} in recurrence cycles depends on three independent factors, which characterize exchange with the two-level system, exchange of L{sub 0} with {l_brace}L{sub n}{r_brace} (R{sub 0} with {l_brace}R{sub n}{r_brace}) and the phonon-induced decay of {l_brace}L{sub n}{r_brace} and {l_brace}R{sub n}{r_brace}. In addition to coherent oscillations with the frequency of the two-level system, {Delta}, and dissipative tunneling with a rate {Delta}{sup 2}/{pi}C{sup 2} (where C is the matrix element of the coupling of L{sub 0} and R{sub 0} with L{sub n} and R{sub n}), a new regime appears where L-R transitions are induced by the partial recovery of the populations of L{sub 0} and R{sub 0} in each recurrence cycle due to synchronous transitions from reservoirs. These transitions induce repeating changes in the populations of the states of the two-level system (Loschmidt echo). The number and width of the echo components increase with the cycle number. Evolution becomes irregular because of the mixing of the contributions from pulses of the neighboring cycles, when the cycle number k exceeds the critical value k{sub c} = {pi}{sup 2}C{sup 2}. Unlike the populations, their cycle-average values remain regular at k Much-Greater-Than k{sub c}. When {Delta} Much-Less-Than {pi}C{sup 2}, the cycle-average populations oscillate with a frequency of {Delta}{Omega}/{pi}C{sup 2} irrespective of mixing. The frequency of oscillations of the populations of the states {l_brace}L{sub n}{r_brace} and {l_brace}R{sub n}{r_brace} is approximately n{Omega}({Delta}/2{pi}C{sup 2}){sup 2}, where {Omega} is the spacing between the neighboring levels of the reservoir and n{Omega} is the difference between the energies of the states L{sub 0} and L{sub n}. The appearance of the mentioned low-frequency oscillations is due to the formation of collective states of the two-level system that are 'dressed' by the reservoir. The predicted oscillations can be detected by femtosecond spectroscopy methods.

• OSTI ID: 22028010
• Journal Information: Journal of Experimental and Theoretical Physics, Journal Name: Journal of Experimental and Theoretical Physics Journal Issue: 4 Vol. 113; ISSN JTPHES; ISSN 1063-7761
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
77 NANOSCIENCE AND NANOTECHNOLOGY
COUPLING
COUPLING CONSTANTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
MATRIX ELEMENTS
MIXING
NANOSTRUCTURES
OSCILLATIONS
PHONONS
PULSES
TUNNEL EFFECT