19 July 2024
Floquet Fermi liquids: Non-equilibrium dance with unique properties

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Understanding Floquet Fermi Liquids

Fermi liquids are quantum mechanical systems where fermions, such as electrons in a metal, exhibit predictable behavior at absolute zero temperature. These systems are governed by Fermi-Dirac statistics, which describe the distribution of fermions in thermal equilibrium. When subjected to a periodic driving force and in contact with a fermionic bath, Fermi liquids can enter a non-equilibrium state known as the Floquet Fermi liquid (FFL). This unique state has garnered interest from researchers due to its intriguing properties and potential applications in electronic systems.

Formation of the Floquet Fermi Liquid

In a Fermi liquid, energy states are continuous, with filled states below the Fermi energy and empty states above it. The Fermi energy level delineates the transition between occupied and unoccupied states at absolute zero. When a periodic force is applied to a Fermi liquid, its energy levels are altered, forming what are known as Floquet bands. These bands represent the modified energy states of the Fermi liquid under the influence of the driving force. The introduction of a fermionic bath further complicates the system, leading to the emergence of a non-steady state termed the Floquet Fermi liquid. This state deviates from the typical Fermi-Dirac statistics observed in equilibrium, displaying a staircase-like pattern of energy state occupation with multiple jumps.

Characteristics and Phenomena of Floquet Fermi Liquids

In the Floquet Fermi liquid state, multiple Fermi surfaces, known as Floquet Fermi surfaces, emerge within the system. These surfaces are nested within each other, creating a layered effect akin to a Russian nesting doll. The presence of these nested Fermi surfaces gives rise to specific phenomena, such as quantum oscillations that manifest as periodic changes in a material’s properties under external parameters like magnetic fields. The interference between different-sized Floquet Fermi surfaces results in observable beating patterns in quantum oscillations, which can be manipulated by tuning the driving force parameters. The ability to control electronic behavior through the manipulation of Floquet Fermi surfaces opens up new possibilities for engineering electronic devices and systems.

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Implications and Future Directions

The study of Floquet Fermi liquids not only sheds light on the behavior of quantum systems under non-equilibrium conditions but also offers potential applications in optoelectronic technologies. Researchers have highlighted the possibility of generating net rectified currents using purely monochromatic light, even within the energy gap of a material. This discovery could pave the way for the development of novel devices such as light amplifiers, sensors, solar cells, and energy harvesting technologies. Moving forward, experimental validation of the Floquet Fermi liquid state and further exploration of its properties could lead to breakthroughs in controlling and manipulating electronic behavior at the quantum level.

Links to additional Resources:

1. www.nature.com/articles/s41567-023-02094-y 2. www.mpi-halle.mpg.de/en/news/2023/beyond-equilibrium-scientists-investigate-floquet-fermi-liquids 3. www.ntu.edu.sg/news/detail/ntu-scientists-make-breakthrough-in-understanding-non-equilibrium-states-of-matter

Related Wikipedia Articles

Topics: Fermi liquid, Floquet bands, Quantum oscillations

Fermi liquid theory
Fermi liquid theory (also known as Landau's Fermi-liquid theory) is a theoretical model of interacting fermions that describes the normal state of the conduction electrons in most metals at sufficiently low temperatures. The theory describes the behavior of many-body systems of particles in which the interactions between particles may be...
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Bloch's theorem
In condensed matter physics, Bloch's theorem states that solutions to the Schrödinger equation in a periodic potential can be expressed as plane waves modulated by periodic functions. The theorem is named after the Swiss physicist Felix Bloch, who discovered the theorem in 1929. Mathematically, they are written where r{displaystyle mathbf...
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Quantum oscillations
In condensed matter physics, quantum oscillations describes a series of related experimental techniques used to map the Fermi surface of a metal in the presence of a strong magnetic field. These techniques are based on the principle of Landau quantization of Fermions moving in a magnetic field. For a gas...
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