# Shyamal K. Bose

Brock University, Physics Department
(905) 688-5550 ext. 3876

Professor, and Associate Dean, FMS Undergraduate Programs
PhD (Simon Fraser), MSc (Dalhousie), MSc (Patna)
Office: MC B202
Phone: (905) 688-5550 ext. 3876
E-mail: bose@brocku.ca

## Research Interests

Non-crystalline materials: calculation of the electronic structure, and transport properties of liquid and amorphous metals, alloys, and semiconductors. Electronic structure, stability, and transport properties of quasicrystals. Vibrational and magnetic properties of amorphous materials. Study of superconductivity based on ab initio electronic structure and electron-phonon coupling calculations. Phase transitions in localized-spin models.

The above is by no means an exhaustive list. My research interests have evolved over the years and covered different areas of condensed matter physics, and I imagine this will be the case in future as well. However, the main thrust of my research efforts has always been theoretical studies of electronic and related properties of condensed matter under the rubric of what is commonly known as ab initio electronic structure studies. By that we mean calculations that are parameter free- the only input is the information about the electronic states of the elements that make up the condensed matter phase. The computational techniques depend on the nature of the system. Liquids and amorphous solids, because of their positional or topological disorder, need a different approach than what can be used for crystalline solids. Random alloys, where there is always an underlying lattice and the disorder lies only in the occupation of the lattice sites by elements of type A or B or C etc. (chemical disorder), can be treated successfully by yet other approaches. Quasicrystals are neither periodic nor strictly aperiodic, and thus, methods suited for both crystalline solids and topologically disordered systems have been used for such cases.

What is the use of studying electronic structure? Well, electronic structure forms the basis of all other studies of the physical properties of the solid; cohesive and phase stability properties, transport properties, lattice vibrational properties, magnetism, superconductivity and so on. Most physical properties of solids and liquids are dictated by the behaviour of the electrons in the atoms that form the building blocks of these systems. It is important that we study and understand these electrons as accurately as possible, so that we can not only better describe the physical properties of these systems but also predict new phases and new materials and fabricate solids and liquids with precisely tailored properties. This is a complex problem, residing at the heart of contemporary materials science and technology programs. My objective is to perform very accurate quantum mechanical studies of the electrons in various condensed matter systems and relate these studies to their magnetic, electrical, superconducting and various other physical properties. I will be working on a class of materials from the viewpoint of their potential application in 'spintronics', an emerging branch of applied physics. Electrons have two fundamental properties: charge and spin. Although the latter invokes in one's mind the picture of a spinning baseball or top, it is fundamentally a quantum mechanical entity. Until now we have only manipulated the flow of 'charge' in electrical circuits and used it to our advantage to build the enormously successful 'electronics' industry. 'Spintronics' is the science of manipulating the other fundamental property of the electron: its spin, and in particular, the flow of spins or the 'spin current'. It is believed that devices based on 'spintronics' will overcome several fundamental limitations of the electronic devices, most of which are related to the loss of energy in the form of heat associated with the flow of charge, the so-called 'charge current'.

Another one of my projects will be aimed at understanding the behaviour of some of the Heusler and shape-memory alloys. The latter are also called smart metals, as upon deformation they remember their original shape to which they can be returned upon heating. These are useful in the aerospace industry and medical technology. In addition, I will also be working on superconducting materials (some of them newly discovered), with the ultimate goal of predicting the existence of new materials with high superconducting transition temperatures.

I also delve into Monte Carlo studies involving models of spin systems, structural, and thermodynamic properties of solids and liquids. These are numerical studies based on the principles of statistical and condensed matter physics.

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Phonon spectrum and electron-phonon coupling (Eliashberg spectral and transport functions) in hcp Fe: ideal c/a ratio, a = 4.6 a.u. ("Pressure dependence of electron-phonon coupling and superconductivity in hcp Fe: A linear response study", Phys. Rev. B, 67, 214518 (2003))

 ---------------------------------------- Unit cell of 1/1 Cd$_6$Yb (spacegroup I23). The Cd (small) and Yb atoms (large) form a shell structure. In the center Cd atoms are located on four vertices of a cube. The next shell (the dodecahedral cavity) consists of Cd atoms placed on the vertices of a dodecahedron. The third shell is a Cd icosidodecahedron composed of triangles and pentagons. Yb atoms are located at the centers of the pentagons. The remaining Cd atoms and Cd atoms of the icosidodecahedra in neighboring unit cells (not shown) form a defect triacontahedron. "Electronic States in 1/1 Cd6Yb and 1/1 Cd6Ca: Relativistic, correlation and structural effects", Phys. Rev. B 70, 184205 (2004). ------------------------------ The regular array of 216 atoms shown on the left is for silicon in diamond structure, which turns into the so-called WWW model of amorphous Si, a 216-atom cluster of amorphous Si shown on the right... ... via local rearrangements of bonds and subsequent relaxation using the Keating potential. Electronic structure of the model is discussed in "Electronic properties of a realistic model of amorphous silicon", S.K. Bose, K. Winer and O.K. Andersen. Phys. Rev B 37, 6262 (1988). WWW stands for F. Wooten, K. Winer and D. Weaire. (see Phys. Rev. Lett. 54, 1392 (1985).)

## Teaching Assignments (2017-18)

• PHYS 5P50 - Advanced Quantum Mechanics I (fall term)
• PHYS 3P90 - Classical Mechanics (winter term)