Spectroscopic Evidence of Ultrafast Topological Phase Transition by Light-Driven Strain

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Controlling topological invariants is crucial for quantum information processing and spintronics, offering potential for efficient spin-current switches.
• Traditional mechanical strain methods for manipulating topological states are limited by in-plane fractures, hindering high-speed applications.
• Bismuth selenide (Bi2Se3) requires significant strain for Z2 topological switching.

Purpose of the Study:

• To investigate light-driven strain-induced topological phase transitions in Bi2Se3 using ultrafast spectroscopy.
• To explore the potential for ultrafast, reversible control over topological invariants.
• To demonstrate a mechanism for high-speed, dissipationless spin-current manipulation.

Main Methods:

• Ultrafast optical spectroscopy
• Terahertz (THz) spectroscopy
• Application of light-induced strain in Bi2Se3

Main Results:

• Experimental evidence of ultrafast switching behavior in Bi2Se3, transitioning from topological insulator to hybridized and normal insulating states.
• Light-induced out-of-plane strain effectively suppresses surface-bulk coupling, allowing surface and bulk conductance differentiation at room temperature.
• Observed coherent conductance modulation at hypersound frequencies due to sudden alterations in surface and bulk transport near the transition point.

Conclusions:

• Light-triggered ultrafast switching of topological invariants in Bi2Se3 is experimentally demonstrated.
• This method provides a promising pathway for high-speed topological switching and related spintronic applications.
• The findings suggest potential for time-dependent manipulation of topological states through photoexcitation intensity control.