# Sergey Vitkalov

Physics

Nonlinear properties of low dimensional systems

85 St Nicholas Terrace

New York , NY 10027

### Education:

- 1986 - Ph.D. at Institute of Solid State Physics of Russian Academy of Science.
- Thesis: "Nonlinear microwave effects in Bismuth at high magnetic field"
- Thesis advisers: V. F. Gantmakher and G. I. Leviev
- 1981 - Master Degree at Moscow Institute of Physics and Technology

### Biography:

**Positions Held**

2007-pres Associate Professor, Physics Department, CCNY

2002-2006 Assistant Professor, Physics Department, CCNY

1998-2002 Research Professor, Research Foundation, CUNY

1997-1998 Research Associate, Chemistry Department, University of Florida

1989-1999 Senior Research Associate, P.N.Lebedev Physical Institute of Russian Academy of Sciences, Russia

1986-1989 Research Associate, P.N.Lebedev Physical Institute of Russian Academy of Sciences, Russia

**Research:**

Research is focused on dynamical and nonlinear properties of low dimensional

electron systems. Goals are to understand fundamental properties of electron

transport in nano-scaled objects leading to practical applications.

**Current grants:**

**1. National Science Foundation** -**DMR: #1104503**

“Quantal Heating of 2D Electrons in Crossed Electric and Quantizing Magnetic Fields” S. A.Vitkalov (PI); 2011-2014;

**2. National Science Foundation - ECCS: #1128459**

“Electron Heating in Superconducting Heterostructures for Advanced Sensing and Communications” S. A. Vitkalov (PI), M. P. Sarachik (Co-PI, CCNY), A. V. Sergeev (Co-PI, SUNY at Buffalo); 2011-2014;

## Current research topics

**Nonlinear Properties of 2D electrons in crossed electric and magnetic field.**

Warming in complex physical systems, in particular global warming, attracts significant contemporary interest. It is essential, therefore, to understand basic physical mechanisms leading to overheating. It is well known that application of an electric field to conductors heats electric charge carriers. Often an elevated electron temperature describes the result of the heating. Our recent ** results** demonstrate that an electric field applied to a conductor with discrete electron spectrum produces a non-equilibrium electron distribution, which cannot be described by a temperature. Such electron distribution changes dramatically the conductivity of highly mobile two dimensional electrons in a magnetic field, forcing them into a state with a **zero differential resistance**. Most importantly the results demonstrate that, in general, **the effective overheating** in the systems with discrete spectrum is significantly stronger than the one in systems with continuous and homogeneous distribution of the energy levels at the same input power.

**Nonlinear response of low dimensional systems**

**Quantum dots:**

Nonlinear directed transport in mesoscopic objects is a subject of considerable fundamental interest due to potential applications in nanoelectronics. At high frequency, the unavoidable breaking of the inverse symmetry of small quantum systems by an impurity potential is reflected in photovoltaic effects. More recently, various competing mechanisms of the rectification in quantum dots have been proposed and found experimentally. Most efforts have been focused on the nonlinear properties of mesoscopic objects in the regime, where the electron transport is governed by quantum interference. In our recent research we study the nonlinear electron transport in a different regime, where the classical ballistic trajectories appear to provide the dominant contribution to the rectification. In magnetic fields we have observed a **gigantic reduction** of the directed electron transport through ballistic dot with lateral size, d = 1 micron, significantly smaller than the mean free path (8 micron) of the electrons in adjoining 2D layers. (see Phys. Rev. Lett. 97, 226807 (2006))

**Micro thermocouple:**

Recently we^{ }reported **measurements of the rectification** of microwave radiation (0.7–20 GHz) at^{ }the boundary between two-dimensional electron systems created by a narrow^{ }gap split gate on a silicon surface. We have found that this tiny system of two different 2D metals work as a controllable thermocouple. We have studied the system of two metals for different temperatures,^{ }electron densities, and microwave power. For frequencies above 4 GHz and^{ }different temperatures, the rectified voltage *V*_{dc} as a function of^{ }microwave power *P* can be collapsed onto a single universal^{ }curve *V*=*f*^{*}(*P*^{*}) using two scaling parameters. The scaled voltage *V*^{ }is a linear function of power *P*^{*} for small power^{ }and proportional to (*P*^{*})^{1/2} at higher power. A theory is^{ }developed which attributes the observed voltage to the thermoelectric response^{ }associated with local heating by the microwave radiation of adjacent^{ }two-dimensional electron systems with different densities *n*_{1} and *n*_{2}. Excellent^{ }quantitative agreement is obtained between theory and experiment. (see Phys. Rev. B 77, 035415 (2008))