PREFACE
What you hold in your hands is not a textbook but rather a guide. A guide
cannot replace the trip itself. Nevertheless, it can give you a hint about the path
to choose, where to turn or to stay, what is worth looking at and thinking about.
If you do not know the local language, a guide may also be used as a phrase-book
telling you how to ask the way or understand the legend on a direction sign.
Usually, a guide-book begins with a large-scale map. Its role in our book
about the country of electrons and disorder in solids is played by a schematic list
of contents (see the back endpaper) explaining the logic of the “administrative
and territorial division of the country”, the specification of its eleven chapters –
provinces and links between them. Nine provinces depicted by white rectangles
are well-known natural topics. The two remaining grey rectangles are specified
by the form and the methods used in the appendices. The section entitled
Percolation Theory summarizes the main concepts underlying this branch of
mathematics. It is present in this book as a comparatively new discipline,
nowadays widely used in physics, which has not been included into standard
university courses for physicists. The section entitled TunnelIVCharacterist-
ics describes experiments which are closely related simultaneously to several
different phenomena such as, e.g., interelectron interference, the Coulomb gap,
hopping conductivity, metal–insulator transitions, etc. By considering this topic
in a individual section, we have tried to avoid unnecessary repetition. We hope
that the reader, once acquainted with this section, would then repeatedly return
to it when reading different topics in the book. Special symbols with a readily
understood meaning indicate the chapters in which the material considered in
the appendices is used.
As a rule, a large-scale map also indicates some contiguous territories indicated
by grey ellipses in our schematic. We also indicate how to reach them: a list of
necessary references and the most important review articles is given at the end
of this preface. The reader is assumed to be well acquainted with such topics as
electrons in an ideal lattice, transport in theτ-approximation, and scattering,
or, at least, to be able to recollect these topics. In fact, no perfect knowledge of
superconductivity or charge-densitywaves isnecessary.
The suggested schematic represents not only a specific list of contents, but
itself contains some unique information. However, one should keep in mind that
since the country on the map is virtual, the map, as the ancient geographic maps,
is far from being objective: its appearance depends on the author’s knowledge and
taste. However, the large contiguous territory named “Interacting Electrons” is
not depicted on our map because, in fact, it is a country of tomorrow. Numerous
discoveries in this land, its development, and road-building are all the deeds of