東華大學圖書館 |

語系: 繁體中文

說明(常見問題)

回圖書館首頁

手機版館藏查詢

登入

回首頁

切換: 標籤 | MARC模式 | ISBD

The Quantum-to-Classical Transition ...

Benatov, Latchezar Latchezarov.

FindBook

Google Book

Amazon

博客來

The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems./
作者:	Benatov, Latchezar Latchezarov.
面頁冊數:	142 p.
附註:	Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.
Contained By:	Dissertation Abstracts International76-01B(E).
標題:	Condensed matter physics. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3633442
ISBN:	9781321132724

The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems.
Benatov, Latchezar Latchezarov.

The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems. - 142 p.

Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.

Thesis (Ph.D.)--Dartmouth College, 2014.

This item must not be sold to any third party vendors.

This thesis comprises two separate but related studies, dealing with two strongly interacting nanoscale systems on the border between the quantum and classical domains. In Part 1, we use a Born-Markov approximated master equation approach to study the symmetrized-in-frequency current noise spectrum and the oscillator steady state of a nanoelectromechanical system where a nanoscale resonator is coupled linearly via its momentum to a quantum point contact (QPC). Our current noise spectra exhibit clear signatures of the quantum correlations between the QPC current and the back-action force on the oscillator at a value of the relative tunneling phase where such correlations are expected to be maximized. We also show that the steady state of the oscillator obeys a classical Fokker-Planck equation, but can experience thermomechanical noise squeezing in the presence of a momentum-coupled detector bath and a position-coupled environmental bath. Besides, the full master equation clearly shows that half of the detector back-action is correlated with electron tunneling, indicating a departure from the model of the detector as an effective bath and suggesting that a future calculation valid at lower bias voltage, stronger tunneling and/or stronger coupling might reveal interesting quantum effects in the oscillator dynamics. In the second part of the thesis, we study the subsystem dynamics and thermalization of an oscillator-spin star model, where a nanomechanical resonator is coupled to a few two-level systems (TLS's). We use a fourth-order Runge-Kutta numerical algorithm to integrate the Schrodinger equation for the system and obtain our results. We find that the oscillator reaches a Boltzmann steady state when the TLS bath is initially in a thermal state at a temperature higher than the oscillator phonon energy. This occurs in both chaotic and integrable systems, and despite the small number of spins (only six) and the lack of couplings between them. At the same time, pure initial states do not thermalize well in our system, indicating that mixed state thermalization stems from the thermal nature of the initial bath state. Under the influence of a thermal TLS bath, oscillator Fock states decay in an approximately exponential manner, but there is also a concave-down trend at very early times, possibly indicative of Gaussian decay. In the case of initial Fock state superpositions, the diagonal density matrix element behaves very similarly to single initial Fock states, while the off-diagonal matrix element decays sinusoidally with an exponentially decreasing amplitude. The off-diagonal decay time is much smaller then the diagonal one, indicating that superposition states decohere much faster than they decay. Both decay times decrease with increasing Fock state number, but more slowly than the 1/n dependence seen in the presence of an external ohmic bath.

ISBN: 9781321132724Subjects--Topical Terms:

3173567
Condensed matter physics.

The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems.
LDR:03860nmm a2200301 4500 001 2059844
005 20150827083006.5
008 170521s2014 ||||||||||||||||| ||eng d
020 $a 9781321132724
035 $a (MiAaPQ)AAI3633442
035 $a AAI3633442
040 $a MiAaPQ $c MiAaPQ
100 1 $a Benatov, Latchezar Latchezarov. $3 3173979
245 1 4 $a The Quantum-to-Classical Transition in Strongly Interacting Nanoscale Systems.
300 $a 142 p.
500 $a Source: Dissertation Abstracts International, Volume: 76-01(E), Section: B.
500 $a Adviser: Miles P. Blencowe.
502 $a Thesis (Ph.D.)--Dartmouth College, 2014.
506 $a This item must not be sold to any third party vendors.
520 $a This thesis comprises two separate but related studies, dealing with two strongly interacting nanoscale systems on the border between the quantum and classical domains. In Part 1, we use a Born-Markov approximated master equation approach to study the symmetrized-in-frequency current noise spectrum and the oscillator steady state of a nanoelectromechanical system where a nanoscale resonator is coupled linearly via its momentum to a quantum point contact (QPC). Our current noise spectra exhibit clear signatures of the quantum correlations between the QPC current and the back-action force on the oscillator at a value of the relative tunneling phase where such correlations are expected to be maximized. We also show that the steady state of the oscillator obeys a classical Fokker-Planck equation, but can experience thermomechanical noise squeezing in the presence of a momentum-coupled detector bath and a position-coupled environmental bath. Besides, the full master equation clearly shows that half of the detector back-action is correlated with electron tunneling, indicating a departure from the model of the detector as an effective bath and suggesting that a future calculation valid at lower bias voltage, stronger tunneling and/or stronger coupling might reveal interesting quantum effects in the oscillator dynamics. In the second part of the thesis, we study the subsystem dynamics and thermalization of an oscillator-spin star model, where a nanomechanical resonator is coupled to a few two-level systems (TLS's). We use a fourth-order Runge-Kutta numerical algorithm to integrate the Schrodinger equation for the system and obtain our results. We find that the oscillator reaches a Boltzmann steady state when the TLS bath is initially in a thermal state at a temperature higher than the oscillator phonon energy. This occurs in both chaotic and integrable systems, and despite the small number of spins (only six) and the lack of couplings between them. At the same time, pure initial states do not thermalize well in our system, indicating that mixed state thermalization stems from the thermal nature of the initial bath state. Under the influence of a thermal TLS bath, oscillator Fock states decay in an approximately exponential manner, but there is also a concave-down trend at very early times, possibly indicative of Gaussian decay. In the case of initial Fock state superpositions, the diagonal density matrix element behaves very similarly to single initial Fock states, while the off-diagonal matrix element decays sinusoidally with an exponentially decreasing amplitude. The off-diagonal decay time is much smaller then the diagonal one, indicating that superposition states decohere much faster than they decay. Both decay times decrease with increasing Fock state number, but more slowly than the 1/n dependence seen in the presence of an external ohmic bath.
590 $a School code: 0059.
650 4 $a Condensed matter physics. $3 3173567
650 4 $a Quantum physics. $3 726746
650 4 $a Physics. $3 516296
690 $a 0611
690 $a 0599
690 $a 0605
710 2 $a Dartmouth College. $b Physics and Astronomy. $3 1036059
773 0 $t Dissertation Abstracts International $g 76-01B(E).
790 $a 0059
791 $a Ph.D.
792 $a 2014
793 $a English
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3633442