Synopsis: It takes two

The voltage created in inclined thin anisotropic films illuminated by laser light is significantly affected by a photovoltaic component.
Synopsis figure
Credit: K. Takahashi et al., Phys. Rev. B (2011)

A significant transverse voltage (more than 10V) has been observed for several inclined-oriented anisotropic thin films when illuminated by laser light. This effect has been attributed to the off-diagonal thermoelectric effect, in which a temperature gradient orthogonal to the film plane induces a voltage parallel to the plane. However, recent results that deviate from the expected behavior of the thermoelectric effect have caused researchers to propose that the induced voltage may be due to an optical and hence nonthermal effect.

Writing in Physical Review B, Kouhei Takahashi and co-workers at Panasonic Corporation in Kyoto, Japan, present measurements of laser-induced voltages in CaxCo02 (x0.5) thin films at different laser wavelengths. The signals behave as expected for energies lower than the band gap of the film, but for energies above the band gap, the signal is smaller than what would be expected from the off-diagonal thermoelectric effect alone. This deviation is consistent with an interband transition, indicating that a small photovoltaic effect is suppressing the voltage signal. By revealing the nature of the different effects on the signal, this experiment helps resolve the controversy of the responsible effect. The results have bearing on applications such as sensitive thermal sensors and thermoelectric generators. – Brad Rubin


Features

More Features »

Announcements

More Announcements »

Subject Areas

OpticsMaterials Science

Previous Synopsis

Superconductivity

Magnetism shortly before pairing

Read More »

Next Synopsis

Atomic and Molecular Physics

Clocking the last century

Read More »

Related Articles

Synopsis: Particle Acceleration with Multiple Laser Pulses
Optics

Synopsis: Particle Acceleration with Multiple Laser Pulses

Trains of laser pulses can be used to accelerate high-repetition-rate electron bunches to high energies. Read More »

Focus: <i>Image</i>—Cooperating Lasers Make Topological Defects
Nonlinear Dynamics

Focus: Image—Cooperating Lasers Make Topological Defects

A circle of interacting lasers is a new model system for exploring topological defects, disordered structures that show up in a wide variety of seemingly unrelated systems. Read More »

Synopsis: Crumpled Graphene
Graphene

Synopsis: Crumpled Graphene

The crumpling of graphene sheets explains a “soft spot” in the material’s mechanical response. Read More »

More Articles