1,062 research outputs found
Irreversibility on the Level of Single-Electron Tunneling
We present a low-temperature experimental test of the fluctuation theorem for
electron transport through a double quantum dot. The rare entropy-consuming
system trajectories are detected in the form of single charges flowing against
the source-drain bias by using time-resolved charge detection with a quantum
point contact. We find that these trajectories appear with a frequency that
agrees with the theoretical predictions even under strong nonequilibrium
conditions, when the finite bandwidth of the charge detection is taken into
account
Full counting statistics of information content
We review connections between the cumulant generating function of full
counting statistics of particle number and the R\'enyi entanglement entropy. We
calculate these quantities based on the fermionic and bosonic path-integral
defined on multiple Keldysh contours. We relate the R\'enyi entropy with the
information generating function, from which the probability distribution
function of self-information is obtained in the nonequilibrium steady state. By
exploiting the distribution, we analyze the information content carried by a
single bosonic particle through a narrow-band quantum communication channel.
The ratio of the self-information content to the number of bosons fluctuates.
For a small boson occupation number, the average and the fluctuation of the
ratio are enhanced.Comment: 16 pages, 5 figure
Full counting statistics for transport through a molecular quantum dot magnet
Full counting statistics (FCS) for the transport through a molecular quantum
dot magnet is studied theoretically in the incoherent tunneling regime. We
consider a model describing a single-level quantum dot, magnetically coupled to
an additional local spin, the latter representing the total molecular spin s.
We also assume that the system is in the strong Coulomb blockade regime, i.e.,
double occupancy on the dot is forbidden. The master equation approach to FCS
introduced in Ref. [12] is applied to derive a generating function yielding the
FCS of charge and current. In the master equation approach, Clebsch-Gordan
coefficients appear in the transition probabilities, whereas the derivation of
generating function reduces to solving the eigenvalue problem of a modified
master equation with counting fields. To be more specific, one needs only the
eigenstate which collapses smoothly to the zero-eigenvalue stationary state in
the limit of vanishing counting fields. We discovered that in our problem with
arbitrary spin s, some quartic relations among Clebsch-Gordan coefficients
allow us to identify the desired eigenspace without solving the whole problem.
Thus we find analytically the FCS generating function in the following two
cases: i) both spin sectors lying in the bias window, ii) only one of such spin
sectors lying in the bias window. Based on the obtained analytic expressions,
we also developed a numerical analysis in order to perform a similar
contour-plot of the joint charge-current distribution function, which have
recently been introduced in Ref. [13], here in the case of molecular quantum
dot magnet problem.Comment: 17 pages, 5 figure
Contiguous 3d and 4f magnetism: towards strongly correlated 3d electrons in YbFe2Al10
We present magnetization, specific heat, and 27Al NMR investigations on
YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic
susceptibility at low temperatures is strongly enhanced at weak magnetic
fields, accompanied by a ln(T0/T) divergence of the low-T specific heat
coefficient in zero field, which indicates a ground state of correlated
electrons. From our hard X-ray photo emission spectroscopy (HAXPES) study, the
Yb valence at 50 K is evaluated to be 2.38. The system displays valence
fluctuating behavior in the low to intermediate temperature range, whereas
above 400 K, Yb3+ carries a full and stable moment, and Fe carries a moment of
about 3.1 mB. The enhanced value of the Sommerfeld Wilson ratio and the dynamic
scaling of spin-lattice relaxation rate divided by T [27(1/T1T)] with static
susceptibility suggests admixed ferromagnetic correlations. 27(1/T1T)
simultaneously tracks the valence fluctuations from the 4f -Yb ions in the high
temperature range and field dependent antiferromagnetic correlations among
partially Kondo screened Fe 3d moments at low temperature, the latter evolve
out of an Yb 4f admixed conduction band.Comment: To appear in Phys. Rev. Let
Keys for successful introduction of ecosan toilets : experiences from an ecosan project in Vietnam
Joint Research on Environmental Science and Technology for the Eart
Energy Dissipation and Fluctuation-Response in Driven Quantum Langevin Dynamics
Energy dissipation in a nonequilibrium steady state is studied in driven
quantum Langevin systems. We study energy dissipation flow to thermal
environment, and obtain a general formula for the average rate of energy
dissipation using an autocorrelation function for the system variable. This
leads to a general expression of the equality that connects the violation of
the fluctuation-response relation to the rate of energy dissipation, the
classical version of which was first studied by Harada and Sasa. We also point
out that the expression depends on coupling form between system and reservoir.Comment: 4 pages, 1 figur
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