Skobeltsyn Institute of Nuclear Physics
Lomonosov Moscow State University

Laboratory of nanostructure physics

The Laboratory of nanostructure physics (LNP) is a part of the Department of microelectronics (LME) of SINP MSU. It was organized in 1999 and integrated research teams apecialized in the fields close to the studies of DSc. Konstantin Likharev at the Physics Department of MSU (Laboratory of cryoelectronics). The Head of the Laboratory is Professor, DSc. Mikhail Kupriyanov.

The Laboratory is equipped with unique home and foreign technological instruments which allow to carry out experimental and theoretical studies at the highest scientific level.

The basic direction of the Laboratiory concerns theoretical and experimental studies of the processes in the metal and molecular nanostructures and based on them devices.

Theoretical research is focused on the studies of electron transport in the nanostructures containing superconducing normal and ferromagnetic materials. Interest in electron transport problems is explained by a number of specific quantum effects which are not only observable, but also beneficial.

First of all, it's Josephson effect according to which in the systems containing more than two superconducting electrodes dissipation-free current flowing is possible regardless type of material providing connection between the electrodes. Electrode-to-elecrode voltage occures when current exceeds some crucial value. Due to presence of potentials difference electromagnetic emission is generated in the structure at the frequency associated with the voltage by the proportionality factor composed from fundamental constants. This effect allows to produce quantum standards of voltage basing on Josephson structures. These standards can repeat both absolute value of the volatage at the levels of 1 and 10 Volts, and the specified signal shape with metrological accuracy. In this field the scientists of the Laboratory cooperate with colleagues from the Institute of Physical Problems (Zelenograd) and Institute of microstructures physics RAS (Nizhny Novgorod).

Nanostructures with superconducting and ferromagnetic materials are rich in a number of non-equilibrium mesoscopic effects. Non-equilibrity of electrons' energy distribution (i.e. its difference from Fermi-like shape) is easily realized in normal metal contacting with superconductor, for instance, by simple specification of direct current across the boundary. Superconducting current flowing in the superconductor transforms into normal current at the length of about length of energy relaxation of electron in normal metal which at low temperature can reach the value of dozens of micrometers. If there are several boundaries, than it is possible to influence on transport between pair electrodes by passing current through another selected electrodes of the nanostructure. In the structures with ferromagnetics presence of exchange field will influence on electron and hole excitations in different ways. Therefore superconducting properties induced from superconductor S in ferromagnetic F do not pass of exponentially as in the case of normal metal, but have oscillation nature. At fixed geometry size of the system it can result in non-monotone behaviour of ctucial temperature of multi-layer SFSFS structures and in temperature oscillations of crucial current of SFS Josephson barrier. Theoretical research of mesoscopic non-equilibrium effects in nanostructers with superconductors is one of the fields of scientific interest of the scientists of the Laboratory. They work in this field in close collaboration with Twente Uniersity (Netherlands), Institute of Solid State Physics (Chernogolovka) and HYPRESS (USA).

Non-euilibrium effects also occur at electromagnetic emission absorption in superconducting films of bolometers and detectors of microwave emission based on SINIS heterostructures. Development of these devices is also one of the directions of the Laboratory activity.

Josephson effect combined with effect of quantization of magnetic flow in the closed superconductive circuits provides an opportunity of production of high-accuracy instruments for magnetic flow measurements (superconductive quantum interferometers) and devices of superfast information processing (rapid single flux quantum logic - RSFQL). First RSFQL-devices were designed at MSU and experimentally produced at the Institute of Radioelectronics RAS. Unlike semiconductor computing systems information in the elements of RSFQL logic is presented not in potential, but in impulse form, i.e. logical unit corresponds not to a specified level of voltage, but to pulse-or-no-pulse within the interval between control clock. As it happens that area of this impulse is determined only by combination of quantum constants, i.e. strictly quantized. Impulses are regenerated by Josephson barriers and spread to the distances of about several cantimeters by striplines and Josephson lines with minimum dissipation and despersion distortions. Recently operation of RSFQL logic is demonstrated at frequency of about 750 GHz and at dissipation level for logic ioperation which is five orders of magnitude lower than at semiconductor analogs. Research in this direction is carried out by the scientists of the Laboratory in cooperation with HYPRESS (USA) and Stony Brook University (USA).

There are theoretical studies of the structures with new high-temperature superconductors - pnictides -materials with complicated mlti-zone electron structire and unusual types of superconductive pairing carried out in the Laboratory. For the first time the scientists of the Laboratory obtained boundary conditions for the contact of the normal metal and multi-zone superconductors basing on the equations of close coupling. The boundary conditions are true beyond approximation of effective mass and allow to take into account both complicated non-parabolic and anisotropic spectrum of normal excitations in the superconductor and their multi-zone nature, and unusual types of symmetry if superconductive parameter of order. Basing on the defined boundary conditions a number of new effects, including interferation of states, belonging to different valleys of multi-zone metal, were predicted. Currently the research is focused in application of the obtained conditions for calculations of parameters and processes in multilayer structures containing pnictides.

With decreasing geometry size of Josephson barrier there occur a new class of quantum mesoscopic effects due to quantization of electric charge - "single electronics". There is an experimental-technological basis in the Laboratory which allows to produce and study the devices where current transport and information storage are provided by single electrons. This research is carried out in close collaboration with scientists from the Laboratory of cryoelectronics of thePhysics Department of MSU. Recently the research team specialized in metallic single-electronics has offered, manufactured and studied original nano-sized structures - prototypes of the future digital and analogous quantum electronics devices, has developed and implemented original methods of production and analysis of wide class of nanostructures, has developed an electrometer sensor, recordly sensitive to the induced elecric charge (about 10^-5 electron's charge/Hz^1/2 ). In this field the scientists of the Laboratory cooperate with Physics-technical Federal Center (Braunschweig, Germany).

There was developed a unique instrument which allows to carry out research of optical properties of nano-objects in the near-field, for instance, to study mechanisms of SHM tunnel current transformation into fluctuating luminescence of null-dimensional semiconductor nanostructures.

The scientists of the Laboratory carry out fundamental intersiciplinary experimental and theoretical studies of physical properties of semiconductor field transistor with a channel-nanowire and its opportunities for application in diagnostics of nanobiosystems and nanoelectronics devices as field/charge sensor. The main emphasis is made in the development of the methods for forming, production and calculation of sensor's paramters with nano-wire geometry intended for local measurements.