The concept of matter waves, also known as de Broglie waves, was proposed by Louis de Broglie, a French physicist. In his doctoral thesis published in 1924, de Broglie put forward the idea that if light can exhibit both wave and particle properties, then perhaps particles like electrons, which were known to behave like particles, could also exhibit wave-like properties. This hypothesis suggested that particles should have a characteristic wavelength associated with them.
De Broglie's proposal was later confirmed experimentally through electron diffraction experiments conducted by Clinton Davisson and Lester Germer in 1927, and independently by George Paget Thomson in the same year. These experiments demonstrated that electrons, which are considered as particles, could indeed exhibit wave-like behavior when interacting with a crystalline material, resulting in diffraction patterns similar to those observed for waves.
De Broglie's work on matter waves played a crucial role in the development of quantum mechanics and had a profound impact on our understanding of the nature of particles at the atomic and subatomic levels. His contribution earned him the Nobel Prize in Physics in 1929.