Interfacial Coupling and Electron-phonon Coupling in van der Waals Heterostructures

Abstract Dirac plasmons in graphene hybridize with phonons of transition metal dichalcogenides (TMDs) when the materials are combined in so-called van der Waals heterostructures (vdWh), thus forming surface plasmon-phonon polaritons (SPPPs). The extend to which these modes are coupled depends on the TMD composition and structure, but also on the plasmons' properties. By performing realistic simulations that account for the contribution of each layer of the vdWh separately, we calculate how the strength of plasmon-phonon coupling depends on the number and composition of TMD layers, on the graphene Fermi energy and the specific phonon mode. From this, we present a semiclassical theory that is capable of capturing all relevant characteristics of the SPPPs. We find that it is possible to realize both strong and ultra-strong coupling regimes by tuning graphene's Fermi energy and changing TMD layer number.

Download Full-text

Interfacial coupling induced critical thickness for the ferroelectric bistability of two-dimensional ferromagnet/ferroelectric van der Waals heterostructures

Physical Review B ◽

10.1103/physrevb.100.235445 ◽

2019 ◽

Vol 100 (23) ◽

Cited By ~ 3

Author(s):

Xiaokun Huang ◽

Guannan Li ◽

Chao Chen ◽

Xin Nie ◽

Xiangping Jiang ◽

...

Keyword(s):

Critical Thickness ◽

Van Der Waals ◽

Two Dimensional ◽

Interfacial Coupling ◽

Van Der Waals Heterostructures

Download Full-text

Intrinsic effect of interfacial coupling on the high-frequency intralayer modes in twisted multilayer MoTe2

Nanoscale ◽

10.1039/d1nr01309b ◽

2021 ◽

Author(s):

Yuchen Leng ◽

Miaoling Lin ◽

Yu Zhou ◽

Jiang-Bin Wu ◽

Da Meng ◽

...

Keyword(s):

High Frequency ◽

Van Der Waals ◽

Interfacial Coupling ◽

Van Der Waals Heterostructures ◽

Intrinsic Effect

The interfacial coupling at the interface makes van der Waals heterostructures (vdWHs) exhibit many unique properties that cannot be realized in its constituents. Such study usually starts with a twist...

Download Full-text

Investigations of Electron-Electron and Interlayer Electron-Phonon Coupling in van der Waals hBN/WSe2/hBN Heterostructures by Photoluminescence Excitation Experiments

Materials ◽

10.3390/ma14020399 ◽

2021 ◽

Vol 14 (2) ◽

pp. 399

Author(s):

Joanna Jadczak ◽

Joanna Kutrowska-Girzycka ◽

Janina J. Schindler ◽

Joerg Debus ◽

Kenji Watanabe ◽

...

Keyword(s):

Physical Properties ◽

Emission Intensity ◽

Van Der Waals ◽

Double Resonance ◽

Strong Increase ◽

Exciting Light ◽

Photoluminescence Excitation ◽

Phonon Coupling ◽

Excitation Light ◽

Electron Phonon Coupling

Monolayers of transition metal dichalcogenides (TMDs) with their unique physical properties are very promising for future applications in novel electronic devices. In TMDs monolayers, strong and opposite spin splittings of the energy gaps at the K points allow for exciting carriers with various combinations of valley and spin indices using circularly polarized light, which can further be used in spintronics and valleytronics. The physical properties of van der Waals heterostructures composed of TMDs monolayers and hexagonal boron nitride (hBN) layers significantly depend on different kinds of interactions. Here, we report on observing both a strong increase in the emission intensity as well as a preservation of the helicity of the excitation light in the emission from hBN/WSe2/hBN heterostructures related to interlayer electron-phonon coupling. In combined low-temperature (T = 7 K) reflectivity contrast and photoluminescence excitation experiments, we find that the increase in the emission intensity is attributed to a double resonance, where the laser excitation and the combined Raman mode A′1 (WSe2) + ZO (hBN) are in resonance with the excited (2s) and ground (1s) states of the A exciton in a WSe2 monolayer. In reference to the 2s state, our interpretation is in contrast with previous reports, in which this state has been attributed to the hybrid exciton state existing only in the hBN-encapsulated WSe2 monolayer. Moreover, we observe that the electron-phonon coupling also enhances the helicity preservation of the exciting light in the emission of all observed excitonic complexes. The highest helicity preservation of more than 60% is obtained in the emission of the neutral biexciton and negatively charged exciton (trion) in its triplet state. Additionally, to the best of our knowledge, the strongly intensified emission of the neutral biexciton XX0 at double resonance condition is observed for the first time.

Download Full-text

Magnetically brightened dark electron-phonon bound states in a van der Waals antiferromagnet

Nature Communications ◽

10.1038/s41467-021-27741-3 ◽

2022 ◽

Vol 13 (1) ◽

Author(s):

Emre Ergeçen ◽

Batyr Ilyas ◽

Dan Mao ◽

Hoi Chun Po ◽

Mehmet Burak Yilmaz ◽

...

Keyword(s):

Ground State ◽

Bound States ◽

Degrees Of Freedom ◽

Coherent Control ◽

Magnetic Order ◽

Van Der Waals ◽

Strong Interactions ◽

Phonon Coupling ◽

Excitation Spectra ◽

Electron Phonon Coupling

AbstractIn van der Waals (vdW) materials, strong coupling between different degrees of freedom can hybridize elementary excitations into bound states with mixed character1–3. Correctly identifying the nature and composition of these bound states is key to understanding their ground state properties and excitation spectra4,5. Here, we use ultrafast spectroscopy to reveal bound states of d-orbitals and phonons in 2D vdW antiferromagnet NiPS3. These bound states manifest themselves through equally spaced phonon replicas in frequency domain. These states are optically dark above the Néel temperature and become accessible with magnetic order. By launching this phonon and spectrally tracking its amplitude, we establish the electronic origin of bound states as localized d–d excitations. Our data directly yield electron-phonon coupling strength which exceeds the highest known value in 2D systems6. These results demonstrate NiPS3 as a platform to study strong interactions between spins, orbitals and lattice, and open pathways to coherent control of 2D magnets.

Download Full-text