Coherent Light-Matter Interactions in Monolayer Transition-Metal Dichalcogenides

1. Front Matter

   Pages i-xvii

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2. Introduction

   • Edbert Jarvis Sie

   Pages 1-11

3. Time-Resolved Absorption Spectroscopy

   • Edbert Jarvis Sie

   Pages 13-25

4. Intervalley Biexcitons in Monolayer MoS2

   • Edbert Jarvis Sie

   Pages 27-36

5. Valley-Selective Optical Stark Effect in Monolayer WS2

   • Edbert Jarvis Sie

   Pages 37-57

6. Intervalley Biexcitonic Optical Stark Effect in Monolayer WS2

   • Edbert Jarvis Sie

   Pages 59-76

7. Large, Valley-Exclusive Bloch-Siegert Shift in Monolayer WS2

   • Edbert Jarvis Sie

   Pages 77-92

8. Lennard-Jones-Like Potential of 2D Excitons in Monolayer WS2

   • Edbert Jarvis Sie

   Pages 93-114

9. XUV-Based Time-Resolved ARPES

   • Edbert Jarvis Sie

   Pages 115-129

This thesis presents optical methods to split the energy levels of electronic valleys in transition-metal dichalcogenides (TMDs) by means of coherent light-matter interactions. The electronic valleys found in monolayer TMDs such as MoS2, WS2, and WSe2 are among the many novel properties exhibited by semiconductors when thinned down to a few atomic layers, and have have been proposed as a new way to carry information in next generation devices (so-called valleytronics). These valleys are, however, normally locked in the same energy level, which limits their potential use for applications. The author describes experiments performed with a pump-probe technique using transient absorption spectroscopy on MoS2 and WS2. It is demonstrated that hybridizing the electronic valleys with light allows one to optically tune their energy levels in a controllable valley-selective manner. In particular, by using off-resonance circularly polarized light at small detuning, one can tune the energy level of one valley through the optical Stark effect. Also presented within are observations, at larger detuning, of a separate contribution from the so-called Bloch--Siegert effect, a delicate phenomenon that has eluded direct observation in solids. The two effects obey opposite selection rules, enabling one to separate the two effects at two different valleys.

• time-resolved absorption spectroscopy
• angle-resolved absorption spectroscopy
• coherent light-matter interactions
• electronic valleys
• valleytronics
• Bloch-Siegert effect
• optical Stark effect
• XUV spectroscopy

• Stanford University, Stanford, USA

  Edbert Jarvis Sie

Edbert Jarvis Sie was awarded a PhD in physics by Massachusetts Institute of Technology in 2017. He is now a postdoctoral research fellow at Stanford University.

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