arXiv subjects

A. I. Larkin

Publications and source records attributed to A. I. Larkin.

45 records · Page 3Linked to original sources

arXiv1997

New quantum phases in a one-dimensional Josephson array

We examine the phase diagram of an ordered one-dimensional Josephson array of small grains. The average grain charge in such a system can be tuned by means of gate voltage. At small grain-to-grain conductance, this system is strongly correlated because of the charge discreteness constraint (Coulomb blockade). At the gate voltages in the vicinity of the charge degeneracy points, we find new phases equivalent to a commensurate charge density wave and to a repulsive Luttinger liquid. The existence of these phases can be probed through a special dependence of the Josephson current on the gate voltage.

cond-mat.mes-hall↗

arXiv1997

Parity Effect in Ground State Energies of Ultrasmall Superconducting Grains

We study the superconductivity in small grains in the regime when the quantum level spacing $δ\varepsilon$ is comparable to the gap $Δ$. As $δ\varepsilon$ is increased, the system crosses over from superconducting to normal state. This crossover is studied by calculating the dependence of the ground state energy of a grain on the parity of the number of electrons. The states with odd numbers of particles carry an additional energy $Δ_P$, which shows non-monotonic dependence on $δ\varepsilon$. Our predictions can be tested experimentally by studying the parity-induced alternation of Coulomb blockade peak spacings in grains of different sizes.

cond-mat.mes-hall↗

arXiv1996

Divergence of the Classical trajectories and Weak Localization

We study the weak localization correction (WLC) to transport coefficients of a system of electrons in a static long-range potential (e.g. an antidot array or ballistic cavity). We found that the weak localization correction to the current response is delayed by the large time $t_E = λ^{-1} |\ln \hbar|$, where $λ$ is the Lyapunov exponent. In the semiclassical regime $t_E$ is much larger than the transport lifetime. Thus, the fundamental characteristic of the classical chaotic motion, Lyapunov exponent, may be found by measuring the frequency or temperature dependence of WLC.

cond-mat↗

arXiv1996

Role of divergence of classical trajectories in quantum chaos

We study logarithmical in $\hbar$ effects in the statistical description of quantum chaos. We found analytical expressions for the deviations from the universality in the weak localization corrections and the level statistics and showed that the characteristic scale for these deviations is the Ehrenfest time, $t_E= λ^{-1}|\ln\hbar|$, where $λ$ is the Lyapunov exponent of the classical motion.

cond-mat↗

arXiv1996

On the superconductivity in the system with preformed pairs

We discuss the phenomenology of the superconductivity resulting from the bose condensation of the preformed pairs coexisting with unpaired fermions. We show that this transition is more mean field like than usual bose condensation, i.e. it is characterized by a relatively small value of the Ginzburg parameter. We consider the Hall effect in the vortex flow regime and in the fluctuational regime above $T_c$ and show that in this situation it is much less than in the transition driven entirely by bose condesation but much larger than in a usual superconductivity. We analyse the available Hall data and conclude that this phenomenology describes reasonably well the data in the underdoped materials of $YBaCuO$ family but is not an appropriate description of optimally doped materials or underdoped $LaSrCuO$.

cond-mat↗

arXiv1995

Peak effect in twinned superconductors

A sharp maximum in the critical current $J_c$ as a function of temperature just below the melting point of the Abrikosov flux lattice has recently been observed in both low and high temperature superconductors. This peak effect is strongest in twinned crystals for fields aligned with the twin planes. We propose that this peak signals the breakdown of the collective pinning regime and the crossover to strong pinning of single vortices on the twin boundaries. This crossover is very sharp and can account for the steep drop of the differential resistivity observed in experiments.

cond-mat↗

arXiv1995

Sign Change of the Flux Flow Hall Effect in HTSC

A novel mechanism for the sign change of the Hall effect in the flux flow region is proposed. The difference $δn $ between the electron density at the center of the vortex core and that far outside the vortex causes the additional contribution to the Hall conductivity $δσ_{xy}=-δn ec/B$. This contribution can be larger than the conventional one in the dirty case $Δ(T)τ<1$. If the carrier density inside the core exceeds that far outside, a double sign change may occur as a function of temperature.

cond-mat↗

arXiv1995

On the spin density wave transition in a two dimensional spin liquid

Strongly correlated two dimensional electrons are believed to form a spin liquid in some regimes of density and temperature. As the density is varied, one expects a transition from this spin liquid state to a spin density wave antiferromagnetic state. In this paper we show that it is self-consistent to assume that this transition is second order and, on this assumption, determine the critical behavior of the $2p_F$ susceptibility, the NMR rates $T_1$ and $T_2$ and the uniform susceptibility. We compare our results to data on high $T_c$ materials.

cond-mat↗

arXiv1993

On the theory of the spin gap in bilayer cuprates

We formulate and solve a model of two planes of antiferromagnetically correlated electrons coupled together by a weak antiferromagnetic interaction of strength $λ$. We show that in-plane antiferromagnetic correlations dramatically enhance the pairing effect of the interplane interaction. For the case where the in-plane correlation length $κ^{-1} \sim T^{-1/2}$, we find that the interaction $λ$ leads to spin pairing at a temperature $T^{*} \sim λ$, much higher than the usual BCS result $exp(-J/λ)$. We suggest that this is a possible explanation of the spin gap effects observed below $T^{*} \sim 150K$ in $YBa_2Cu_3O_{6.6}$.

cond-mat↗