Topological Materials

09.04.2025

Topological Materials

Why in the news?   

The United Nations has declared 2025 as the International Year of Quantum Science and Technology, marking 100 years since quantum theory began to revolutionise science.

What are Topological Materials?

• Topological materials are substances that exhibit different physical properties on their surface and in their interior.
• These materials may behave like a metal on the outside (conducting electricity) but like an insulator on the inside (not conducting electricity).
• The term "topological" refers to the unique geometric and quantum properties of the material, which remain unchanged even if the shape of the material is distorted.
• Discovered in the latter half of the 20th century, these materials represent a new class of quantum matter.
• Nobel Prize in Physics (2016) was awarded to scientists (David Thouless, Duncan Haldane, and Michael Kosterlitz) for their theoretical discoveries in this field.

How do they work?

• These materials exhibit a metallic surface (conducting electrons freely) while maintaining an insulating core (electrons remain localized).
• This strange duality arises from quantum mechanical effects, especially the topology of electronic band structures.
• The behaviour is deeply rooted in the principles of quantum mechanics, where electron spin and momentum interplay due to a phenomenon called spin-orbit coupling.
• The interaction of light and matter, the collective behavior of electrons, and phase transitions are governed by quantum principles.
• The UN declared 2025 as the International Year of Quantum Science and Technology, marking 100 years since the foundation of quantum mechanics.

Why do Metals and Insulators differ?

• In metals, electrons are free to move — like a soup of charge, allowing conduction of electricity and heat.
• In insulators, electrons are bound tightly to their atoms and do not move freely, hence they do not conduct electricity.
• When light (an electromagnetic wave) hits these materials:
• In metals, electrons move collectively and reflect light.
• In insulators, electrons move individually, allowing light to pass through.

                               Source: The Hindu

Consider the following statements regarding Topological Materials:

1.Topological materials are substances that exhibit different physical properties on their surface and in their interior.

2.These materials may behave like a metal on the outside (conducting electricity) but like an insulator on the inside (not conducting electricity).

 3.The term "topological" refers to the unique geometric and quantum properties of the  material.

How many of the statements given above are correct?

A.Only one

B.Only two

C.All three

D.None

Answer C