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


More Announcements »

Subject Areas

OpticsMaterials Science

Previous Synopsis


Magnetism shortly before pairing

Read More »

Next Synopsis

Atomic and Molecular Physics

Clocking the last century

Read More »

Related Articles

Viewpoint: Relaxons Heat Up Thermal Transport
Materials Science

Viewpoint: Relaxons Heat Up Thermal Transport

A recasting of the theory that underlies thermal transport in electrical insulators relies on new vibrational modes called relaxons. Read More »

Synopsis: Hydrogen  Bonding Comes to the Rescue
Chemical Physics

Synopsis: Hydrogen Bonding Comes to the Rescue

Hydrogen bonding may safeguard biomolecules against the damaging effects of UV light. Read More »

Viewpoint: Cold Results from Fast Lasers

Viewpoint: Cold Results from Fast Lasers

Ultrafast lasers show promise to cool down and trap atomic species inaccessible to more traditional methods. Read More »

More Articles