Floquet-Engineered Valleytronics in Dirac Systems

Kundu, Arijit; Fertig, H. A.; Seradjeh, Babak

doi:10.1103/physrevlett.116.016802

Cited by 88 publications

(63 citation statements)

References 38 publications

(57 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the last few years, the concept of engineering such periodically driven systems, often called Floquet systems, has gained prominence, particularly due to the feasibility of experiments in solid state 6 as well as in photonic 7 and cold atom systems 8 . Floquet topological systems have been studied extensively to predict non-equilibrium Majorana modes [9][10][11] , non-trivial transport properties [12][13][14][15] as well as to control the band-structure 3,16,17 .…”

Section: Introductionmentioning

confidence: 99%

Brillouin-Wigner theory for Floquet topological phase transitions in spin-orbit-coupled materials

et al. 2016

Self Cite

View full text Add to dashboard Cite

We develop the high frequency expansion based on the Brillouin-Wigner (B-W) perturbation theory for driven systems with spin-orbit coupling which is applicable to the cases of silicene, germanene and stanene. We compute the effective Hamiltonian in the zero photon subspace not only to order O(ω −1 ), but by keeping all the important terms to order O(ω −2 ), and obtain the photoassisted correction terms to both the hopping and the spin-orbit terms, as well as new longer ranged hopping terms. We then use the effective static Hamiltonian to compute the phase diagram in the high frequency limit and compare it with the results of direct numerical computation of the Chern numbers of the Floquet bands, and show that at sufficiently large frequencies, the B-W theory high frequency expansion works well even in the presence of spin-orbit coupling terms.

show abstract

Section: Introductionmentioning

confidence: 99%

Brillouin-Wigner theory for Floquet topological phase transitions in spin-orbit-coupled materials

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…This two-dimensional (2D) material has been grown experimentally by successful deposition of silicene sheet on silver substrate [9][10][11] . Also the interest in silicene soared due to the possibility of its various future applications ranging from spintronics [13][14][15][16][17] , valleytronics [18][19][20][21][22] to silicon based transistor 23 at room temperature. Very recently, it has been reported that low energy excitations in silicene follows relativistic Dirac equation akin to graphene 7,24 .…”

Section: Introductionmentioning

confidence: 99%

Thermal conductance by Dirac fermions in a normal-insulator-superconductor junction of silicene

2016

View full text Add to dashboard Cite

We theoretically study the properties of thermal conductance in a normal-insulatorsuperconductor junction of silicene for both thin and thick barrier limit. We show that while thermal conductance displays the conventional exponential dependence on temperature, it manifests a nontrivial oscillatory dependence on the strength of the barrier region. The tunability of the thermal conductance by an external electric field is also investigated. Moreover, we explore the effect of doping concentration on thermal conductance. In the thin barrier limit, the period of oscillations of the thermal conductance as a function of the barrier strength comes out be π/2 when doping concentration in the normal silicene region is small. On the other hand, the period gradually converts to π with the enhancement of the doping concentration. Such change of periodicity of the thermal response with doping can be a possible probe to identify the crossover from specular to retro Andreev reflection in Dirac materials. In the thick barrier limit, thermal conductance exhibits oscillatory behavior as a function of barrier thickness d and barrier height V0 while the period of oscillation becomes V0 dependent. However, amplitude of the oscillations, unlike in tunneling conductance, gradually decays with the increase of barrier thickness for arbitrary height V0 in the highly doped regime. We discuss experimental relevance of our results.

show abstract

“…Our finding reveals more general valley selection rules and promises enhanced control over the valleytronic properties of Dirac materials, such as graphene, TMDs, as well as Weyl semimetals. Furthermore, by using higher pump intensity or lower pump photon energy with selective light helicity, we expect to reveal higher-order coherent effects that could produce polarized valley current in transport experiments [114].…”

Section: Discussionmentioning

confidence: 99%

Coherent Light-Matter Interactions in Monolayer Transition-Metal Dichalcogenides

Sie

2018

Springer Theses

View full text Add to dashboard Cite

Semiconductors that are thinned down to a few atomic layers can exhibit novel properties beyond those encountered in bulk forms. Transition-metal dichalcogenides (TMDs) such as MoS 2 , WS 2 and WSe 2 are prime examples of such semiconductors. They appear in layered structure that can be reduced to a stable single layer where remarkable electronic properties can emerge. Monolayer TMDs have a pair of electronic valleys which have been proposed as a new way to carry information in next generation devices, called valleytronics. However, these valleys are normally locked in the same energy level, which limits their potential use for applications.This dissertation presents the optical methods to split their energy levels by means of coherent light-matter interactions. Experiments were performed in a pump-probe technique using a transient absorption spectroscopy on MoS 2 and WS 2 , and a newly developed XUV light source for time and angle-resolved photoemission spectroscopy (TR-ARPES) on WSe 2 and WTe 2 . Hybridizing the electronic valleys with light allows us to optically tune their energy levels in a controllable valley-selective manner. In particular, by using off-resonance circularly polarized light at small detuning, we can tune the energy level of one valley through the optical Stark effect. At larger detuning, we observe 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, which enables us to separate the two effects at two different valleys.Monolayer TMDs also possess strong Coulomb interaction that enhances many-body interactions between excitons, both bonding and non-bonding interactions. In the former, bound excitonic quasiparticles such as biexcitons play a unique role in coherent light-matter interactions where they couple the two valleys to induce opposite energy shifts. In the latter, non-bonding interactions between excitons are found to exhibit energy shifts that effectively mimics the Lennard-Jones interactions between atoms. Through these works, we demonstrate new methods to optically tune the energy levels of electronic valleys in monolayer TMDs. AcknowledgmentsFirst and foremost, I would like to thank my advisor Prof. Nuh Gedik for his mentorship and support. He has been a constant source of inspiration since I first started my graduate studies. Actually it was even before that. I remember my first meeting at a conference in Boston where he presented a real-time image of crystalline lattice motion. The idea of watching Michael Jackson performing Billie Jean flashed through my head, because he was that cool and inspiring, and he continues to be so. He has been a tremendous support since day one, where I was given the opportunity to design and build the XUV beamline for ARPES in the lab as well as the freedom to build the white-light setup next to it. His vigor to make new innovations in timeresolved experiments is always inspiring. Throughout my graduate studies, he...

show abstract

Floquet-Engineered Valleytronics in Dirac Systems

Cited by 88 publications

References 38 publications

Brillouin-Wigner theory for Floquet topological phase transitions in spin-orbit-coupled materials

Brillouin-Wigner theory for Floquet topological phase transitions in spin-orbit-coupled materials

Thermal conductance by Dirac fermions in a normal-insulator-superconductor junction of silicene

Coherent Light-Matter Interactions in Monolayer Transition-Metal Dichalcogenides

Contact Info

Product

Resources

About