Display device and display method

A display device comprising:

• an optical cell including:
• a first electrode;
• a second electrode;
• an ion conduction layer facing the first electrode and the second electrode and containing a mobile ion;
• and
• a first nanostructure provided between the first electrode and the ion conduction layer, the first nanostructure being electrically connected to the first electrode, having a first plasmon resonance wavelength in a visible light region, and containing a first metal element,
• a first metal compound layer containing the first metal element contained in the first nanostructure and having a refractive index different from a refractive index of the ion conduction layer, the first metal compound layer being formed on at least a part of a surface of the first nanostructure by applying a voltage between the first electrode and the second electrode, and
• an amount of the first metal compound layer being different between in a first state and in a second state, a first voltage being applied between the first electrode and the second electrode in the first state, a second voltage different from the first voltage being applied between the first electrode and the second electrode in the second state.