# Ultrafast room-temperature valley manipulation in silicon and diamond

## TL;DR

Researchers demonstrated a fast method to control electron valleys in silicon and diamond at room temperature, which could lead to new types of electronic devices.

## Contribution

An ultrafast optical technique for valley manipulation in bulk semiconductors at room temperature is introduced.

## Key findings

- Electron valley populations can be controlled using femtosecond infrared pulses in silicon and diamond.
- The method operates on subpicosecond timescales and is compatible with silicon-based technology.
- This technique enables potential terahertz valleytronic devices at room temperature.

## Abstract

Some semiconductors have more than one degenerate minimum of the conduction band in their band structure. These minima—known as valleys—can be used for storing and processing information, if it is possible to generate a difference in their electron populations. However, to compete with conventional electronics, it is necessary to develop universal and fast methods for controlling and reading the valley quantum number of the electrons. Even though selective optical manipulation of electron populations in inequivalent valleys has been demonstrated in two-dimensional crystals with broken time-reversal symmetry, such control is highly desired in many technologically important semiconductor materials, including silicon and diamond. We demonstrate an ultrafast technique for the generation and read-out of a valley-polarized population of electrons in bulk semiconductors on subpicosecond timescales. The principle is based on the unidirectional intervalley scattering of electrons accelerated by an oscillating electric field of linearly polarized infrared femtosecond pulses. Our results are an advance in the development of potential room-temperature valleytronic devices operating at terahertz frequencies and compatible with contemporary silicon-based technology.

Control over electron populations in different conduction band minima in semiconductors can be used to store and process information. Now the ultrafast optical manipulation of such electrons at room temperature has been demonstrated in silicon and diamond.