MaPWave · Designing Many-Particle Wavefunctions in Mesoscopic Quantum Devices

Designing Many-Particle Wavefunctions in Mesoscopic Quantum Devices

Project Context: The overarching goal of “MaPWave” is to define the electronic structure and carrier dynamics of 2D semiconductor quantum devices by directly engineering the quantum wavefunctions of the charge carriers.This requires access to the energy- and momentum-dependent quantum states in micro- and nano-scale devices. The plan is to combine state-of-the-art electron spectroscopies with femtosecond time-resolution and nano-scale spatial resolution in order to overcome these challenges and demonstrate that electronic and optoelectronic properties of quantum devices composed of 2D transition metal dichalcogenides (TMDCs) can be engineered at the level of the fundamental electronic wavefunctions. Overall Objectives: I. Preparation of electron-hole pair wave function: The idea is to use the method of stacking the dissimilar TMDCs WS2,MoS2 and WSe2 as a primary approach to engineer the quantum states of 2D semiconductors. The electronic band gaps of these materials are staggered, thereby making it possible to excite a hole in one material while an electron is excited in the other when exposed to a light pulse. Strong Coulomb interactions between these oppositely charged excitations leads to the formation of an interlayer electron-hole pair, which is called an interlayer exciton. These quasiparticles follow the Bose-Einstein quantum statistics such that they can condense into a single quantum state –i.e., a Bose-Einstein condensate. These collective many-body states are highly robust with long lifetimes that make them extremely attractive for both energy harvesting and storage, as well as for quantum information technology where they can be utilized as fault-tolerant qubits. The preparation of the many-body wavefunction associated with such a condensate and obtain quantitative information on electron-hole binding energies, lifetime and density, which dictate the quantum efficiency of the materials. 2. Tuning many-body interactions with superlattices: Introducing a lattice mismatch via a finite twist angle between stacked 2D semiconductors leads to a moiré superlattice. The long-range potential of such a moiré can be tuned using the twist angle, leading to momentum-shifted replicas of the quantum states with distinct interacting exciton condensates. Direct measurement of the extent of localization of such superlattice excitons and determine their lifetime depending on the superlattice, which will ultimately widen the scope of potential optoelectronic applications of the materials. 3.Transfermation of electronic properties: Stacks of TMDCs will be integrated in field-effect device architectures, enabling control of the charge carrier concentration in the materials using an electrostatic gate electrode. Doping the materials with extra electrons leads to the possibility of inducing conducting states that would induce a semiconductor-to-metal transition. Depending on interaction strength, which is controlled by carrier concentration, temperature and twist angle, the charged excitations around the Fermi level of the doped system could form charge ordered or superconducting states. By inducing and tuning these states, which demonstrates complete quantum control of basic electronic properties and function.

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